Indiana University-Purdue University Indianapolis (IUPUI) / Tissue cells display mechanosensitivity in their ability to discern and respond to changes in the viscoelastic properties of their surroundings. By anchoring and pulling, cells are capable of translating mechanical stimuli into a biological response through a process known as mechanotransduction, a pathway believed to critically impact cell adhesion, morphology and multiple cellular processes from migration to differentiation. While previous studies on polymeric gels have revealed the influence of substrate elasticity on cellular shape and function, a lack of suitable substrates (i.e. with mobile cell-substrate linkers) has hindered research on the role of substrate viscosity. This work presents the successful design and characterization of lipid-bilayer based cell substrates of tunable viscosity affecting cell-substrate linker mobility through changes in viscous drag. Here, two complementary membrane systems were employed to span a wide range of viscosity. Single polymer-tethered lipid bilayers were used to generate subtle changes in substrate viscosity while multiple, polymer-interconnected lipid bilayer stacks were capable of producing dramatic changes in substrate viscosity. The homogeneity and integrity of these novel multibilayer systems in the presence of adherent cells was confirmed using optical microscopy techniques. Profound changes in cellular growth, phenotype and cytoskeletal organization confirm the ability of cells to sense changes in viscosity. Moreover, increased migration speeds coupled with rapid area fluctuations suggest a transition to a different migration mode in response to the dramatic changes in substrate viscosity.

Yes / The presence of lubricant droplets in the gas that flows through the piston assembly and crankcase of an internal combustion engine (generically termed oil misting) has important implications for performance, particularly lubricant supply to the upper piston assembly, oil consumption and lubricant degradation. A significant source of these droplets is thought to be oil shearing and blow-through by blow-by gas flows in the piston assembly. An experimental rig was developed to simulate the high velocity gas and lubricant film interactions at a top piston ring gap where the flow conditions are most severe. Flows of lubricant droplets were produced and characterised in terms of the proportion of the oil flow that formed droplets in the gas flow and the size distribution of the droplets produced. Considering various aspects of a commercial automotive crankcase formulation, the effect of lubricant viscosity was found to be particularly important. Of the lubricant additives evaluated, viscosity modifiers were found to have the greatest effect on the tendency to form droplets: Detailed study on a range of viscosity modifiers identified that the influence of their molecular architectures on viscoelasticity was the key mechanism.

No description available.

[pt] Esta dissertação de mestrado aborda um estudo aprofundado do artigo [2]. No Capítulo 2, são introduzidas as definições e conceitos fundamentais necessários para a análise teórica subsequente. Uma proposição é demonstrada, estabelecendo a existência de uma expansão de Taylor para funções em um determinado espaço, enfatizando o papel do expoente de Escauriaza. O capítulo continua apresentando dois lemas que relacionam subsoluções e supersoluções em termos de viscosidade e propriedades de normas. A primeira versão do lema considera a relação entre a dimensão do espaço e a norma, enquanto a segunda versão utiliza o expoente de Escauriaza para obter resultados mais refinados. Também são apresentados dois resultados que explicam a relação entre diferentes noções de soluções viscosas e sua conexão com os espaços de Sobolev. As propriedades dos operadores de Pucci são discutidas como conclusão deste capítulo. No Capítulo 3, a dissertação estabelece a definição da geometria da fronteira do domínio em questão. Em seguida, um importante lema é demonstrado, estabelecendo a existência de soluções fortes em um determinado espaço, explorando a regularidade das funções envolvidas com base nesse lema. Os conceitos de super-diferenciabilidade e sub-diferenciabilidade são introduzidos, desempenhando um papel crucial na compreensão do comportamento das soluções viscosas e suas relações com derivadas de ordem superior. Um resultado geral que amplia essas definições é apresentado. Duas versões em que a função u é duas vezes super-diferenciável são discutidas, considerando o espaço Ld e posteriormente o espaço Lp , de modo que p menor que d. A dissertação prossegue demonstrando a relação entre sub-solução Lp-viscosidade e sub-solução Lp-forte quando u pertence a um espaço específico. Em seguida, é mostrado que os limites uniformes de soluções também são soluções. Por fim, é apresentado o resultado principal da dissertação, demonstrando a unicidade das soluções fortes. / [en] This master s thesis delves into an in-depth study of the article [2]. Chapter2 begins by introducing fundamental definitions and concepts essential forthe subsequent theoretical analysis. A proposition is then demonstrated,establishing the existence of a Taylor expansion for functions in a givenspace, emphasizing the role of the Escauriaza exponent.The chapter proceeds to present two lemmas that relate subsolutions andsupersolutions in terms of viscosity and properties of norms. The firstversion of the lemma considers the relationship between the dimension ofspace and the norm, while the second version uses the Escauriaza exponentto obtain more refined results. Two results are shown to explain that explainthe relationship between different notions of viscous solutions and theirconnection with Sobolev spaces.The properties of the Pucci operators are discussed at the conclusion of thischapter. Chapter 3 begins by establishing the definition of the boundarygeometry of the domain in question. An important lemma is demonstrated,which establishes the existence of strong solutions in a given space andexplores the regularity of the functions involved based on this lemma.The concepts of superdifferentiability and subdifferentiability areintroduced, playing a crucial role in understanding the behavior of viscoussolutions and their relationships with higher order derivatives. A generalresult that extends these definitions is presented. The dissertation discussestwo versions wherein the function u is twice super-differentiable, consideringthe space Ld and later the space Lp, so that p less than d.The dissertation goes on to demonstrate the relationship between Lp-viscosity sub-solution and Lp-strong sub-solution when u belongs to aspecific space. Next, it is shown that the uniform limits of solutions arealso solutions. Finally, the main result of the dissertation is presented,demonstrating the uniqueness of strong solutions.

The focus of this dissertation is the development of a fundamental understanding of the acoustics and piezoelectric transducer governing the operation of piezoelectric inkjets and horn-based ultrasonic atomizers when utilizing high viscosity working fluids. This work creates coupled, electro-mechanical analytical models of the acoustic behavior of these devices by extending models from the literature which make minimal simplifications in the handling terms that account for viscous losses. Models are created for each component of the considered fluid ejectors: piezoelectric transducers, acoustic pipes, and acoustic horns. The acoustic pipe models consider the two limited cases when either the acoustic boundary layer or attenuation losses dominate the acoustic field and are adapted to account for changes in cross-sectional area present in acoustic horns. A full electro-mechanical analytical model of the fluid ejectors is formed by coupling the component models using appropriate boundary conditions. The developed electro-mechanical model is applied to understand the acoustic response of the fluid cavity alone and when combined with the transducer in horn-based ultrasonic atomizers. An understanding of the individual and combined acoustic response of the fluid cavity and piezoelectric transducer allow for an optimal geometry to be selected for the ejection of high viscosity working fluids. The maximum pressure gradient magnitude produced by the atomizer is compared to the pressure gradient threshold required for fluid ejection predicted by a hydrodynamic scaling analysis. The maximum working fluid viscosity of the standard horn-based ultrasonic atomizer and those with dual working fluid combinations, a low viscosity and a high viscosity working fluid to minimize viscous dissipation, is established to be on the order of 100mPas. The developed electro-mechanical model is also applied to understand the acoustic response of the fluid cavity and annular piezoelectric transducer in squeeze type ejectors with high viscosity working fluids. The maximum pressure gradient generated by the ejector is examined as a function of the principle geometric properties. The maximum pressure gradient magnitude produced by the ejector is again compared to the pressure gradient threshold derived from hydrodynamic scaling. The upper limit on working fluid viscosity is established as 100 mPas.

The viscosity and density of bis(8-methylnonyl) benzene-1,2- dicarboxylate {diisodecyl phthalate (DIDP)}, with a nominal viscosity at T = 298 K and p = 0.1 MPa of 87 mPa•s, have been measured at temperatures from (298.15 to 423.15) K and pressures from (0.1 to 70) MPa. A vibrating wire viscometer, with a wire diameter of about 0.15 mm, was utilised for the viscosity measurements and the results have an expanded uncertainty, (k = 2), including the error arising from the pressure measurement, of between ±(2 and 2.5) % The density was determined with two vibrating tube densimeters one for operation at p≈0.1 MPa with an expanded uncertainty (k = 2) of about ±0.1 %, the other that used at pressures up to 70 MPa, with an estimated expanded uncertainty (k = 2) of about ±0.3 %. Measurements of density and viscosity were performed on three samples of DIDP each with different purity stated by the supplier and as a function of water mass fraction. The measured viscosity and density are represented by interpolating expressions with differences between the experimental and calculated values that are comparable with the expanded (k = 2) uncertainties. The obtained viscosities at p = 0.1 MPa agree with values reported in the literature within the combined expanded (k = 2) uncertainties of the measurements while our densities differ by no more than 1.5 %. Viscosity data at p > 0.1 MPa deviate systematically from the literature values in the range of -10 % to 10 %. An apparatus capable of simultaneously measuring the solubility of a gas dissolved in a liquid and the viscosity and the density of the resulting mixture over a wide temperature and pressure range was constructed and tested. Preliminary results have been reported.

Mayonnaise is a mixture of egg yolk, vinegar, water, spices and 70-80% oil forming a semi-solid oil-in-water emulsion. When preparing a low-fat mayonnaise with an increased water content, thickening agents are required for increased viscosity and emulsion stability. The hydrocolloids xanthan gum and guar gum are sometimes used for this purpose and they act synergistically creating a viscosity increase. However, guar gum has poor acid stability, and because mayonnaise is an acidic product guar gum will eventually start to degrade causing a viscosity decrease and subsequent emulsion separation. Despite this fact, guar gum and xanthan gum are extensively used in mayonnaises today. The aim of this degree project was to explore how the synergy between guar gum and xanthan gum influences the viscosity of a low fat mayonnaise and whether high acidity will have an impact on the viscosity over a 4-week period. This was to examine if and if so, how a mayonnaise recipe can be modified to maintain a cost efficient product with the desired rheological properties in times of hydrocolloid price fluctuations. The study was conducted by preparing 15 mayonnaises with 50% fat, either at pH 3,5; 4 or 5 and a total of 0,6 % hydrocolloids with varying proportions of guar gum and xanthan gum. The mayonnaise samples were studied by measurements of viscosity, color changes and a visual comparison of their mayonnaise-like flow-properties compared to Hellmann’s Real Mayonnaise used as reference. The viscosity of the mayonnaises increased with increasing ratio of guar gum. On the other side, there were greater viscosity losses in mayonnaises with increasing ratio of guar gum 4 weeks after preparation compared to 4 days, with no apparent signs of correlation between higher acidity and hydrocolloid degradation. Mayonnaises with 20% xanthan gum and 80% guar gum had the texture most similar to the reference. In these low-fat mayonnaises, the use of more xanthan gum led to an undesired “slimy” texture and a lower viscosity – an important aspect if adjusting a low-fat mayonnaise recipe by increasing the ratio of xanthan gum. Because a commercial mayonnaise sometimes is consumed several months after manufacturing, that time frame is most likely required in order to fully measure how much the high acidity in mayonnaise will affect its viscosity. This project has shown a pattern where viscosity in the assessed mayonnaises starts to decrease a few weeks after preparation. However to find out exactly to what extent and how this would affect the overall product, and ultimately: if guar gum/xanthan gum combinations are suitable for long-term mayonnaise applications, further studies are required. / Viskositet och syrastabilitet i majonnäs med låg fetthalt och olika proportioner av xantan och guarkärnmjöl Majonnäs är en blandning av äggula, vinäger, vatten, kryddor och 70-80% olja som bildar en semi-solid olja-i-vatten-emulsion. För att tillverka en lågfettsmajonnäs med högre vatteninnehåll behöver förtjockningsmedel tillsättas för viskositet och emulsionsstabilitet. Hydrokolloiderna xantangummi och guarkärnmjöl används ibland i detta syfte och de utövar en synergi som ger ökad viskositet. Dock har guarkärnmjöl dålig syrastabilitet och eftersom majonnäs är en sur produkt kommer guarkärnmjölet efter ett tag att brytas ned vilket leder till en viskositetsminskning och emulsionsseparation. Trots detta används guarkärnmjöl och xantangummi i stor utsträckning i majonnäser idag. Syftet med examensarbetet var att undersöka hur synergin mellan guarkärnmjöl och xantangummi påverkar viskositeten i en lågfettsmajonnäs och huruvida en hög syrahalt kommer att påverka viskositeten under en 4-veckorsperiod. Detta för att se om och i så fall hur ett majonnäsrecept kan modifieras för att erhålla en kostnadseffektiv produkt om priset på hydrokolloider växlar. För arbetet bereddes 15 majonnäser med 50% fetthalt, antingen med pH 3,5; 4 eller 5 och totalt 0,6% hydrokolloider med olika proportioner av guarkärnmjöl och xantangummi. Majonnäserna undersöktes genom mätning av viskositet, färgförändringar och en visuell jämförelse av deras majonnäsliknande flytegenskaper i förhållande till Hellmann’s Real Mayonnaise som användes som referens. Viskositeten i majonnäserna ökade med ökande halt guarkärnmjöl. Å andra sidan minskade viskositeten i högre grad med ökande halt guarkärnmjöl 4 veckor efter tillverkning jämfört med 4 dagar, men inga tydliga samband mellan högre syrahalt och nedbrytning av hydrokolloider syntes. Majonnäser med en blandning av 20% xantangummi och 80% guarkärnmjöl hade den konsistens som var mest lik referensen. I dessa försök med lågfettsmajonnäser ledde användandet av högre halt xantangummi till en oönskad ”slimig” textur och en lägre viskositet – en viktig aspekt om ett recept på lågfettsmajonnäs ska modifieras genom att öka halten xantangummi. Eftersom en kommersiell majonnäs ibland konsumeras flera månader efter tillverkning så är det troligtvis den tidsramen som krävs för att helt kunna mäta hur mycket den höga syrahalten i majonnäs kommer att påverka dess viskositet. Detta projekt har påvisat ett mönster där viskositeten i de analyserade majonnäserna börjar minska några veckor efter tillverkningen. Men för att få reda på exakt i vilken utsträckning och hur detta skulle påverka produkten i sin helhet, och i slutändan: om kombinationen med guarkärnmjöl och xantangummi är lämplig för majonnäser med lång hållbarhet krävs ytterligare studier.

Real-time, bedside observation of patient clotting is essential in various surgeries in the operating room (OR), but specifically during cardiac surgeries. The objective of this thesis is to design and test a new piezoelectric device that can be used for viscoelasticity measurement with time as a Point of Care (POC) test. Slow turnaround times (TAT) of current methods to monitor blood viscoelastic changes in patients have led to excessive bleeding and the need for blood transfusions in many situations (Despotis et al, 1997). This study shows that the phase shift produced by a resonator sensor can be related to the viscosity of a liquid. By monitoring a phase shift between an actuator and sensor pair, a numeric relationship can be generated and suffice as a calibration curve for each probe. At a calculated error averaging a maximum of 2%, and coefficient of determination and correlation coefficient exceeding 0.95, two probes have been tested in various glycerin solutions and prepared for whole blood experimentation. They have also been tested in varying temperatures to simulate effectiveness in a dynamic environment, similar to that of clotting whole blood.

La variété de l'offre alimentaire actuelle incite à l'hyperphagie qui est en partie responsable de la prise de poids corporel. Réduire la consommation est ainsi devenu une contrainte pour une certaine partie de la population. Dans ce contexte, les fibres, qui sont des glucides non-digestibles dans l'intestin grêle, permettent de réduire la prise alimentaire, d'atténuer les sensations de faim et/ou d'augmenter les sensations de satiété. Cependant, les mécanismes comportementaux, périphériques et centraux à l'origine de ces effets sont mal-connus. Leur capacité à maintenir cet effet anorexigène en présence d'autres nutriments comme les lipides et les protéines a également été très peu étudiée.L'étude de ces mécanismes est l'objet de cette thèse. Des fibres telles que la gomme de guar (GG) fortement viscosifiante et le fructo-oligosaccharide (FOS) très fermentescible ont été administrées, en début de journée, aux souris sous forme de solution à raison de 700 µL et à une dose de 3%, 5% et 14% via un gavage intra-gastrique. Cette étude a montré que les solutions fortement visqueuses, notamment le GG 5% et le mélange GG-FOS 14% étaient les seules capables d'exercer un effet anorexigène à court terme comparées aux solutions moins visqueuses comme l'eau, le GG 3%, le FOS 14% et les solutions de nutriments comme les protéines (peptides de caséine) et les lipides (huile de colza) qui fournissent 10% de l'ingéré calorique quotidien des animaux (1.2 kcal). Pour le cas du mélange visqueux GG-FOS 14%, la baisse de la prise alimentaire est due au rassasiement (réduction de 50% de la taille et de la durée du repas dans les 30 premières minutes post-ingestion). Cette baisse, non compensée jusqu'à la fin de la journée, n'est pas associée à une aversion gustative conditionnée. Ce rassasiement est dû à l'intégration au niveau du centre de contrôle de la taille du repas (NTS), des signaux vagaux de distension gastrique et de la cholecystokinine (CCK). Quand les fibres visqueuses GG 5% et GG-FOS 14% sont mélangées avec des protéines, elles perdent leur effet anorexigène. L'action de les mélanger avec les lipides a par contre montré que seul le mélange visqueux GG-FOS 14% est capable d'exercer un effet anorexigène. L'effet anorexigène du mélange lipide et GG-FOS 14% est dû au niveau de chaque repas aux signaux mécaniques gastriques et CCK vagaux, et à l'axe PYY- système mélanocortique hypothalamique pour le maintien de l'effet sur la journée.En conclusion, les fibres visqueuses sont des nutriments qui peuvent participer au contrôle de la prise alimentaire en stimulant le rassasiement. Elles sont capables de maintenir cet effet en milieu lipidique. Elles pourraient ainsi être ajoutées aux aliments riches en lipides pour mieux contrôler la prise alimentaire et le poids corporel. / The various types of food currently marketed encourage people to eat more, thus leading to weight gain, and reducing food intake has become challenging. To help deal with this, it was shown that dietary fibers decreased food intake and/or feelings of hunger while increasing those of satiety. However, the behavioral, peripheral and central mechanisms underlying this phenomenon are not well known. This study was undertaken in order to characterize these mechanisms. Dietary fibers such as the highly viscous guar gum (GG) and the highly fermentable fructo-oligosaccharide (FOS), in doses of 3%, 5% and 14%, were given to mice by intra-gastric gavage of 700 µL volume. It appeared that highly viscous fibers such as GG 5% and the mixture GG-FOS 14% were able to decrease food intake compared to less viscous preloads such as water, FOS and nutrient solutions (protein solution with casein peptides, lipid solution with rapeseed oil supplying 1.2 kcal or 10% of daily energy intake in mice). Specifically, the mixture GG-FOS 14% induced satiation by reducing the size and duration of meals during the first 30 min post-treatment. This effect was neither compensated for by the end of the day, nor was it associated with conditioned taste aversion. The GG-FOS 14% -induced satiation was due to gastric distension and vagal CCK signaling which were integrated at the level of the NTS, a nucleus controlling meal size. Moreover, mixing GG 5% and GG-FOS 14% with protein abolished their food intake inhibitory effect. In contrast, when mixed with lipid, GG-FOS 14% maintained its anorexigenic effect. The mixture of lipid and GG-FOS 14% stimulated satiation which involved vagal CCK signaling, gastric distension and the NTS. Additionally, the communication between systemic PYY and melanocortic neurons at the level of the hypothalamus was implicated in the anorexigenic effect of this mixtureIn conclusion, viscous dietary fibers can control food intake by stimulating satiation. They are able to maintain their anorexigenic effect in lipid media such that they can be added to foods containing more fat in order to control food intake and body weight.

Master of Science / Food Science / Sajid Alavi / Pulp/paste candy is popular in Mexico and is gaining popularity around the world. Pulp/paste candy is characterized as a soft, semi-fluid candy with particles in a colloidal suspension, typically squeezed out of the package for consumption. It is made by hydrating gums in water and mixing them with corn syrup, acid, powdered/pulverized sugar, and other minor ingredients yielding a product around 80°Brix and pH between 2-3. Over time the sucrose in the candy tends to invert, causing two types of failure: package leakage and solidification in package. Based on the findings of previous work from Molina-Rubio et al. (2010), a modified semi-liquid syrup model system was created with corn syrup, sugar, gums, and water. The model system was used to identify the influence these ingredients had on viscosity and texture since these factors are linked to the typical modes of failure in pulp/paste candy. An oscillatory sweep was used on a controlled force rheometer to identify the linear viscoelastic range. Oneway ANOVA with Tukey HSD was used to compare % total solids levels with complex viscosity at 0.1 rad/sec (there was a significant difference between all levels) and minimum tan (delta) (mid and high level were similar). Using a stepwise method, ANOVA models were generated that showed statistically significant effects on complex viscosity for gum level and sugar level as well as interactions (p < 0.05) between invert syrup-water, gum-water, and sugar type-water. The type of gum and the amount of corn syrup used didn’t significantly impact on the viscosity of the system. Using probe tests helped to analyze samples that were too thick for the rheometer. Analysis showed an inflection point for exponentially increased hardness (85-93%TS) that should be further investigated. The stepwise regression model generated for stickiness showed that the invert syrup-water interaction was significant along with gum type. These results are applicable to the confectionery industry and can help companies test and create a candy that meets the packaging and shelf life constraints that they desire. Targeting invert syrup-water levels and the hydration of the gum will have the most impact on the final product’s viscosity and stickiness, which are important for primary package filling and storage. To create an easy to eat candy, no invert syrup should be used in formulation and gellan gum would be better to use than xanthan. Higher solids (> 85%) should also be avoided since it would create a candy that is harder to squeeze out of the package due to higher viscosity and textural hardness.