Milk derived ingredients from the production of cheese and butter can be used as vehicles for nutrients. Buttermilk is a nutritious product of milk that comes from the churning of cream into butter. One of the advantages of buttermilk is that it is enriched in milk fat globule components, such as phospholipids and forms emulsions with fat when treated with high shear. The objective of this work was to explore the effects of shear on regular buttermilk and whey buttermilk in terms of liposomal aggregate size and chemical composition. The effects of microfluidization at 2000 psi and homogenization at 2000 psi/500 psi on the particle size distribution of liposomal aggregates between whey buttermilk (WBM) at pH 4.6 and 6.8 and commercial sweet buttermilk (SBM) at pH 4.60 were compared with whey protein isolate (WPI) at pH 4.6. At pH 6.80, WPI and SBM are too soluble in water to measure particle size but WBM is not as soluble. From this investigation, the mean particle diameter of the SBM aggregates at pH 4.6 decreased after the first pass through the microfluidizer and the same is true, after homogenization. SBM aggregates at pH 4.6 had a significantly larger mean particle diameter before treatments in both shear processes compared to WPI at pH 4.6 and WBM at pH 4.6 and WBM at pH 6.8 (p < 0.0001). WPI at pH 4.6 and WBM at both pH showed no significant differences in their mean particle size in both homogenized and microfluidized treatments. WPI and SBM samples resulted in significant particle diameter differences vi from before to after homogenizing at pH 4.6. SBM at pH 4.6 had significantly larger average particle diameter than WBM at pH 4.6 (p < 0.0002), WPI at pH 4.6 (p < 0.0002) and WBM at pH 6.8 (p < 0.0045) before microfluidization at pass 0. WBM and WPI across all treatments showed very similar tendencies in small particle size attributes and some similarities in protein composition. In addition, the small aggregate size of WBM is suggested to be influenced by the presence of phospholipids and thus, creating significantly smaller mean particles compared to SBM even before inducing high shear. In contrast, treated and untreated SBM differed from WBM in phospholipid composition in both homogenization and microfluidization techniques. WBM samples contained more phospholipids than SBM, whereas WPI samples contained very low concentrations of phospholipids. Through HPLC analysis, WPI, SBM, and WBM showed different profiling of the phospholipid classes. These differences may be due structural changes of the aggregates from shearing, initial thermal treatments or hydrophobic and/or protein-phospholipid interactions between the aggregates. SBM samples also exhibited different protein profiling than WBM and WPI samples. This study suggests that high shear and presence of phospholipids impact the size distribution of liposomal aggregates through structural alterations. The aggregates can be utilized as a novel ingredient and in the processing of dairy foods to deliver nutrition.

Dans cette thèse on utilise une méthode de Galerkin discontinue (GD) pour modéliser la propagation des ondes dans un matériau endommagé. Deux modèles différents pour la description de l’endommagement ont été considérés. Dans la première partie de la thèse on utilise un modèle d’endommagent assez général, basé sur une modélisation micromécanique. Pour ce modèle on établit un critère de stabilité basé sur une densité critique de fissuration. On développe aussi une méthode numérique GD capable de capturer les instabilités au niveau microscopique. On construit une solution exacte pour analyser la précision de la méthode proposée.Plusieurs résultats numériques vont permettre d’analyser la propagation des ondes dans les configurations planes et anti-planes. Dans la deuxième parte de la thèse on étudie la propagation des ondes dans un milieux fissuré (microfissures en contact avec frottement). La méthode numérique développée utilise une technique GD et la méthode du Lagrangien augmenté. En utilisant cette méthode on a pu calculer numériquement la vitesse de propagation moyenne dans un matériau endommagé. On a pu comparer les résultats obtenus avec les formules analytiques obtenues avec des approches micromécaniques. Finalement, on a utilisé les calculs numériques pour étudier la propagation des ondes après un impact sur une plaque céramique pour les deux modèles mécaniques considérés. / A discontinuous Galerkin (DG) technique for modeling wave propagation in damaged (brittle) materials is developed in this thesis. Two different types of mechanical models for describing the damaged materials are considered. In the first part of the thesis general micro-mechanics based damage models were used. A critical crack density parameter, which distinguishes between stable and unstable behaviors, wascomputed. A new DG-numerical scheme able to capture the instabilities and a micro-scale time step were proposed. An exact solution is constructed and the accuracy of the numerical scheme was analyzed. The wave propagation in one dimensional and anti-plane configuration was analyzed through several numerical computations. In the second part of the thesis the wave propagation in cracked materials with a nonlinear micro-structure (micro-cracks in frictional contact) was investigated. The numerical scheme developed makes use of a DG-method and an augmented Lagrangian technique. The effective wave velocity in a damaged material, obtained by a numerical upscaling homogenization method, was compared with analytical formula of effective elasticity theory. The wave propagation (speed, amplitude and pulse length) in micro-cracked materials in complex configurations was studied. Finally, numerical computations of blast wave propagation,for the both models, illustrate the role played by the micro-cracks orientation and by the friction.

Three different concentrated whole milks (2.5x, 2.75x, and 3.0x) were produced by mixing equal parts of ultrafiltration retentate of whole milk and reverse osmosis retentate of the UF milk permeate. The concentrated whole milks were ultra-high temperature processed by direct steam injection (140.6°C) followed by flash cooling and two-stage homogenization pressures (2500/500 psi, 3500/700 psi, or 4500/900 psi). The milk concentrates were packaged aseptically and stored at room temperature. On the other hand, the milk concentrates produced by the RO single membrane system with the same concentration levels served as the control. Physicochemical properties of the milks were surveyed every 2 weeks during a 6-month storage period. The milk concentrates combined from the blending of multiple-membrane retentates showed the expeected concentrations of all major nutrients except nonprotein nitrogen. A 20% to 32% shortage of nonprotein nitrogen permeated through the RO membrane during the production of the concentrated whole milks. Over the 6 months' storage, nonprotein nitrogen content did not significantly change in the 2.5x, 2.75x, and 3.0x concentrated whole milks. No microbial growth or enzyme activity was measured or observed in the samples collected. Milk concentrated 2.5x with 4500/900psi homogenization pressure did not show cream plug formation during the first 5 months of storage. Milk concentrated 2.75x with 4500/900 psi homogenization pressure had the approximate cream plug level of the 2.5x concentrated milk at 4 months of storage. Milk concentrated 3.0x with 4500/900 psi homegenization pressure showed cream plugging at 2.5 months. As higher homogenization pressure was applied to the milk concentrates, less creaming occurred at all milk concentration levels. Homogenization at all pressures did not reduce or eliminate sedimentation during storage. The milk concentrates from the control RO membrane processing showed less sedimentation than did the concentrates from the multiple membrane system at the same homogenization pressure (2500/500 psi). the higher the concentration of total milk solids, the more sedimentation occurred. Viscosity was not affected by homogenization pressure in any of the concentrated whole milks.

Natural fibers have drawn attention of researchers as an environmentally-friendly alternative to synthetic fibers. Developing natural fiber reinforced bio-composites are a viable alternative to the problems of non-degrading and energy consuming synthetic composites. This study focuses on (i) the application of kenaf fiber as a potential reinforcement and, (ii) determining the tensile properties of the randomly oriented short kenaf fiber composite both experimentally and numerically. Kenaf fiber micro-structure and its Young's modulus with varying gage length (10, 15, 20, and 25.4 mm) were investigated. The variation in tensile strength of kenaf fibers was analyzed using the Weibull probability distribution function. It was observed that the Young's modulus of kenaf fiber increased with increase in gage length. Fabrication of randomly oriented short kenaf fiber using vacuum bagging techniques and hand-lay-up techniques were discussed and the tensile properties of the specimens were obtained experimentally. The tensile modulus of the composite sample at 22% fiber volume fraction was found to be 6.48 GPa and tensile strength varied from 20 to 38 MPa. Numerical models based on the micro mechanics concepts in conjunction with finite element methods were developed for predicting the composite properties. A two-step homogenization procedure was developed to evaluate the elastic constants at the cell wall level and the meso-scale level respectively. Von-Mises Fisher probability distribution function was applied to model the random orientation distribution of fibers and obtain equivalent modulus of composite. The predicted equivalent modulus through numerical homogenization was in good agreement with the experimental results.

The popularity of cosmetic surgery in the U.S. has increased dramatically over the last ten years - particularly for women, who make up the largest group of cosmetic surgery consumers. Cosmetic surgery can include relatively simple procedures such as permanent hair removal or Botox to more complicated procedures like breast augmentations and face-lifts. The rise in popularity of cosmetic surgery exalts only one kind of beauty and excludes many women from ever attaining this ideal, so while women may feel empowered, surgery acts as a form of assimilation, because the act of cosmetic surgery reifies an exclusionary beauty norm. With cosmetic surgery, this hegemonic ideal is becoming more attainable, and in the process, some women modify their individual identities, which I argue are shaped by such things as ethnicity, age, body shape, wrinkles, etc., and instead tend to become one homogenized group. I also argue that cosmetic surgery is a form of colonization of the body because most people who do fit with what is perceived as normal and beautiful experience pressure to assimilate. The body becomes colonized (via surgery) much as a country does in the sense that the colonizing group otherizes the colonized, and deems their way of life, or culture, as abhorrent and in need of assimilation to the dominant groups way of life. The colonizers (creators of the beauty myth) seek to modify womens identities in order to suit the beauty ideal. The modification of identity is a possibility because some of the most common procedures such as rhinoplasty, eyelid surgery, and Botox, seek to eliminate, or downplay, ethnic, or age associated traits in exchange for traits that adhere to the beauty ideal. External markers such as an ethnic nose, or even wrinkles, help define women and link them to their cultural origins or individual identity. Society has deemed such markers, particularly for women, as unacceptable because they are not in line with the U.S.'s beauty ideal, therefore, cosmetic surgery, and the inevitable the move towards monoculturalism threatens women's identities.

Le but de la thèse est d'étudier l'homogénéisation d'équations de convection-diffusion singulières et de problèmes spectraux à poids indéfini. La thèse se compose de deux parties. La première partie contient des résultats qualitatifs et asymptotiques pour les solutions d'équations de type convection-diffusion stationnaires et instationnaires, qui sont définies dans des domaines bornés ou nonbornés. Les problèmes examinés comprennent des études qualitatives pour une équation elliptique avec des termes du premier ordre dans un cylindre semi-infini, l'homogénéisation de modèles de convection-diffusion dans des cylindres minces et une analyse asymptotique d'équations de convection-diffusion instationnaires avec un grand terme du premier ordre, posées dans un domaine borné. La deuxième partie de la thèse porte sur l'homogénéisation de problèmes spectraux à poids indéfini, pouvant changer de signe. On montre que le comportement asymptotique dépend essentiellement de la moyenne du poids, notamment si la moyenne est nulle ou non nulle. On construit alors le développement asymptotique du spectre dans les deux cas.

Essential oils (EOs) or their isolated components, such as eugenol and carvacrol, have strong antimicrobial activities against both Gram-positive and Gram-negative bacteria and are generally recognized as safe by the FDA. However their hydrophobic properties limit their dispersion and stabilization in aqueous food systems. This requires higher concentrations, which in turn negatively affect the quality of foods. The objective here was to determine the effect of the natural emulsifier lecithin on the antimicrobial activity of eugenol and carvacrol and possible food applications. Escherichia coli K12 and E. coli O157:H7 strains ‘Cider’ and ATCC 43889 were used. Homogenized eugenol and carvacrol, with and without lecithin, were screened for antimicrobial activity. The stability of the samples measured by particle size and zeta potential was not affected by different concentrations of lecithin. For all strains, the antimicrobial activity of carvacrol and eugenol was enhanced significantly (P<0.05) by low concentration of lecithin. The D-value (time at a specific concentration of antimicrobial necessary to cause a 90% reduction in viable cells) for E. coli K12 exposed to 0.047% v/v eugenol or 0.015 % v/v carvacrol was reduced from 13.3 to 6.3 min and 17.4 to 9.7 min, respectively, with the addition of 0.0025% lecithin (w/v). Similarly 0.0025% w/v lecithin in the presence of 0.058% v/v eugenol or 0.0188% v/v carvacrol, caused the D-value to decrease from 4.0 to 1.2 min and 10.2 to 6.9 min, respectively, for E. coli strain ‘Cider’ and from 6.2 min to 3.6 min and 9.9 to 5.4 min, respectively, for E. coli ATCC 43889. Higher lecithin concentrations (> 0.005% w/v) increased D-values compared to lower concentrations. Similar results were found in vegetable juice. The results showed that a small amount of lecithin can enhance the antimicrobial activities of essential oils. Addition of lecithin had no effect on oil-water emulsion droplet particle size and the stability of the samples was not affected by different concentration of lecithin. We believe that lecithin enhances the antimicrobial activity of eugenol and carvacrol droplets by improving the ionic interactions between the positively charged lecithin-containing essential oil components and negatively charged bacterial cells.

In this dissertation we develop and analyze numerical method to solve general elliptic boundary value problems with many scales. The numerical method presented is intended to capture the small scales effect on the large scale solution without resolving the small scale details, which is done through the construction of a multiscale map. The multiscale method is more effective when the coarse element size is larger than the small scale length. To guarantee a numerical conservation, a finite volume element method is used to construct the global problem. Analysis of the multiscale method is separately done for cases of linear and nonlinear coefficients. For linear coefficients, the multiscale finite volume element method is viewed as a perturbation of multiscale finite element method. The analysis uses substantially the existing finite element results and techniques. The multiscale method for nonlinear coefficients will be analyzed in the finite element sense. A class of correctors corresponding to the multiscale method will be discussed. In turn, the analysis will rely on approximation properties of this correctors. Several numerical experiments verifying the theoretical results will be given. Finally we will present several applications of the multiscale method in the flow in porous media. Problems that we will consider are multiphase immiscible flow, multicomponent miscible flow, and soil infiltration in saturated/unsaturated flow.

This work focuses on a new beta metastable titanium alloy, Ti-5553, for aeronautical applications. The goals of this study are the characterization of the two phases (alpha and beta) of this titanium alloy and the numerical modeling of representative cells of this material, which will be used to determine the appropriate microstructure. This thesis is divided into several parts. First, the numerical tools necessary to characterize this alloy and to model representative cells using the periodic homogenization theory will be presented. Secondly, the body-centered cubic beta phase will be identied. Then, the third part will concentrate on the characterization of the hexagonal close-packed alpha phase. Finally, the last part of this thesis will focus on choosing and modeling representative cells containing the phases identfied in the previous parts. The experimental tensile tests performed at different strain rates have demonstrated the necessity of using an elastic-viscous-plastic constitutive law. Guided by macroscopic (tensile and simple shear) experiments, a microscopic plasticity-based constitutive law was chosen to characterize this alloy instead of a macroscopic Norton-Hoff's constitutive one. It will be shown that the beta phase can be fully maintained in macroscopic samples at room temperature, making the characterization of the material behavior of this phase possible from macroscopic experiments. The optimized set of parameters was validated on nanoindentation tests performed in different beta grain orientations. In addition, a sensitivity analysis of several parameters from nanoindentation tests was performed and shows the importance of accurately defining some parameters, such as the exact shape of the indenter, and the negligible influence of other parameters, such as Poisson's ratio. From this study of experimental and numerical nanoindentation tests, it also appears that the orientation of the beta grain indented hardly affects the nanoindentation results. The characterization of the alpha phase was performed using nanoindentation experimental tests available for different grain orientations. This choice was influenced by the impossibility of maintaining only an alpha phase in a macroscopic Ti-5553 sample at room temperature and by the failure to represent the phase accurately from macroscopic (alpha+beta) samples. The material characterization of this phase is complex and difficulties occur when the behavior of this phase has to be characterized for different orientations by only one set of parameters. Finally, experimental microstructures were chosen and their simplied corresponding representative cells were meshed. Numerical simulations of these representative cells were performed and the influence of several parameters will be studied, such as the effect of the appearance of the alpha phase in the beta matrix and the effect of the shape of the alpha phase on the behavior of the cell.

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