In this paper, we study Bézier surfaces in View the MathML source three-dimensional Minkowski space. In particular, we focus on timelike and spacelike cases for Bézier surfaces. We also deal with the Plateau¿Bézier problem in View the MathML source, obtaining conditions over the control net to be extremal of the Dirichlet function for both timelike and spacelike Bézier surfaces. Moreover, we provide interesting examples showing the behavior of the Plateau¿Bézier problem in View the MathML source and illustrating the relationship between it and the corresponding Plateau¿Bézier problem in the Euclidean space R3.

Dans un avenir proche, les dispositifs de détection médicaux miniaturisés en temps réels (lab-on-chip) seront au centre de la révolution des méthodes de diagnostics médicaux et d’identification des processus biologiques et cela, autant au niveau clinique qu’au niveau de la recherche. Pour y arriver, il est important de développer des chimies de surface stables et spécifiques, ce qui demande une compréhension des interactions intermoléculaires à l’interface liquide/solide. Pour bien comprendre ces interactions, il est important de développer des instruments adaptés à la mesure près de l’interface liquide/solide des différentes caractéristiques à identifier. Ce projet de recherche présente la conception, la fabrication et les expériences tests d’un capteur multimodal pour l’identification de processus biologiques à l’interface basés sur des technologies de résonance des plasmons de surface (SPR) et de microcalorimétrie. Ces deux technologies mises ensemble vont permettre d’effectuer des mesures de la cinétique des interactions ainsi que des caractéristiques thermodynamiques. En premier lieu, les caractéristiques d’une interaction intermoléculaire à l’interface d’une réaction d’hybridation d’ADN furent définies afin d’en déduire un cahier des charges pour les transducteurs. Suite à cela, la conception des transducteurs microcalorimétriques et SPR furent réalisés en tenant compte des contraintes de chacun des transducteurs. Suite à la conception théorique des différentes parties du capteur, un procédé de fabrication compatible avec les méthodes de fabrication standard de la microélectronique fut défini et testé. Afin de s’assurer de la fonctionnalité des dispositifs ainsi fabriqués, des tests de fonctionnalisation de surface furent appliqués sur les échantillons afin de tester la compatibilité du procédé de fonctionnalisation avec les méthodes de fabrication et avec une chimie de surface type. Pour terminer, un système de mélange actif fut testé et caractérisé avec le dispositif de microcalorimétrie afin de s’assurer qu’il était possible de mélanger les fluides avec les produits biologiques pour s’assurer de la qualité de la réaction de surface. Le système développé pourra être utilisé pour effectuer la mesure d’hybridation d’ADN à l’interface. Le système intègre deux modalités permettant la caractérisation en temps réel des interactions intermoléculaires à l’interface liquide/solide. Ce type de système permet la mesure de la cinétique de différents modèles biologiques tels que les puces à sucre encore certains récepteurs cellulaires ou la mesure de conformation moléculaire à l’interface. Des mesures d’oxydation du glucose catalysée par la glucose oxydase sont montrées.

The growth and morphology of fibroblasts cultured on a physically and chemically modified surface was investigated. The need to understand cellular relationships with surface topography and chemistry is essential in the fields of biomedical engineering and biotechnology. It is well documented that mammalian cell behavior senses and responds to the surrounding micro- and nano- scale environment, but the research defining the chemistry, surface architecture, and material properties for control of this behavior is still in its infancy. The cell response to a substrate is complex, involving membrane proteins, extracellular matrix (ECM), cytoskeletal rearrangement, and changes in gene expression. Conventional cell culture is carried out on two-dimensional (2-D) cell culture platforms, such as polystyrene (PS) or glass, and forces cell behavior to adapt and adhere to an unnatural, planar environment. The biological behavior of these cells is used as a starting point for drug screening, implant design, and metabolic processes, but this is a misrepresentation of cells in their native environment. This discrepancy may be hampering biological research or initiating experimental efforts that are invalid. This body of work seeks to address these issues and contains established protocols for inexpensive, pseudo three-dimensional (3-D) culture scaffolds. The research described offers a multi-disciplinary approach for fabrication of biomaterials to achieve user defined or in vivo cell behavior using human fibroblasts. To provide insight into the design of alternative cell culture templates we have analyzed cell-surface interactions and characterized the surface properties. The substrates fabricated utilized micro-roughened surface topography with 2 – 6 µm wide features and surface chemistry as a method for controlling cell behavior. Surface roughness was templated onto polydimethylsiloxane (PDMS) and PS. The fabricated polymer surfaces have been characterized by atomic force microscopy (AFM), contact angle goniometry, fluorescence microscopy, and infrared (IR) spectroscopy. Initial studies of the textured surface yielded a super-hydrophobic surface with a 154° contact angle and high surface adhesion that was investigated using surface free energy calculations. This was followed by modification of the micro-roughness with self-assembled monolayers (SAMs), proteins, or thin films of polymer for use as a culture platform for cells. Cell behavior on the modified polymers was compared and analyzed against unmodified surfaces and tissue culture PS dishes. Cell morphology on rough PDMS surface was altered by the surface topography decreasing the average cell area to 1760 µm2 compared to an average cell area of 3410 µm2 on smooth PDMS. Gene expression changes were also noted with a 2.3 fold increase in the matrix metalloproteinase, MMP14, in cells on the rough surface compared to cells cultured on Petri dishes. Surface roughness was also combined with other surface modification methods for cell culture, including cell alignment and cell sheet engineering. 50 µm wide lines of fibronectin (FN) patterned on the rough PDMS induced cell directionality while still maintaining a pseudo 3-D culture system creating the first cell culture surface of its kind. The micro-roughness was also templated onto PS and chemically modified with a thermo-responsive polymer. This novel surface produced confluent cell sheets that detached from the surface when cooled below 32°C. Cell sheets cultured on the modified PS surfaces had an increase in FN fibril formation stimulated by the surface roughness when compared to cell sheets detached from a smooth, control surface. The minor alterations to surface topology were proven to be effective in modifying cell biochemical response compared to cells cultured on flat substrates. Differences in surface topography and chemistry stimulated changes in cell adhesion, cytoskeletal arrangement, ECM composition, and gene expression. These cell properties were used as markers for comparison to native cell systems and other reports of 3 D culture scaffolds. The mechanism of altering cell response is discussed in each chapter with respect to the specific type of surface used and compared to cell response and behavior on planar culture systems. New fabrication procedures are described that include the incorporation of other surface modification techniques such as SAMs, surface patterning, and thermo-responsive polymer grafting with surface roughness for original cell culture platforms to mimic an in vivo environment. The research presented here demonstrates that micro- and nano- changes to surface topography have large impacts on the cell-surface relationship which have important implications for research and medical applications involving adherent cells.

A range of geochemical reactions are controlled by the interfacial characteristics of rocks and minerals. Many engineered and natural systems are affected by geochemical reactions that occur at interfaces. Asphalt-aggregate adhesion in road construction is influenced by the interfacial characteristics of the aggregate. Likewise, the remediation of nonaqueous-phase liquid contaminants, such as trichloroethylene or methyl tert-butyl ether, is controlled by the interactions between mineral surfaces and the organic liquid. Many natural systems are also influenced by reactions at interfaces. The migration of petroleum in sedimentary basins is influenced by the wettability of the surfaces of the basin pore space. Adhesion of organisms, such as bacteria or lichens, to rock surfaces is controlled by the interactions of proteins and mineral surfaces. Rock and mineral surfaces are described by surface energy. Surface energy is a thermodynamic construct defined as the amount of work required to form more of a surface. Surface energy can be divided into van der Waals, Lewis acid, and Lewis base components. The ability to predict the magnitude of surface energy components is valuable in understanding species behavior. Surface energy is controlled by three master variables: surface chemistry, surface morphology, and surface coatings. While the surface energy of a number of minerals and aggregates has been characterized, there has not yet been a comprehensive study of the surface energies of a variety of the most common minerals and aggregates using consistent methodology. In addition there has not yet been a study of the effect of these three master variables on surface energies of natural minerals and rocks. This study measured the surface energy of 22 common minerals and 7 aggregates. The samples’ bulk and surface chemistries were characterized with wavelength and energy dispersive spectra analyses on an electron microprobe and x-ray photoelectron spectroscopy. The XPS was also used to quantify the organic and inorganic coatings on the surfaces. Results showed that van der Waals surface energy is typically between 40 and 60 ergs/cm2. Polar surface energy varies by 1 to 3 orders of magnitude, and thus is likely the most important component in accounting for changes between natural minerals.

ABSTRACT SYNTHESIS AND CHARACTERIZATION OF SURFACE SULFONATED POLYPROPYLENE FILMS Ecevit, Safiye Tuba M.S., The Department of Polymer Science and Technology Supervisor: Leyla Aras, Prof. Dr. Co- Supervisor: Teoman Tin&ccedil / er, Prof. Dr. March 2004, 44 pages The basic reseach on the surface sulfonation of the polypropylene is very important due to the surface design for higher functionalization. For this purpose, liquid-phase sulfonation of the polypropylene surfaces at various temperatures for different time periods were performed by concentrated sulphuric acid. The physical and chemical changes formed by the effect of the sulfonation on the polypropylene surfaces were determined by contact angle measurement, mechanical analysis, UV-Vis spectrometer, differential scanning calorimeter (DSC) and scanning electron microscopy (SEM). The surface polarity and wetting properties of the samples were evaluated by contact angle measurement. It is seen that, sulfonation at low temperatures and short time periods improve these two properties of the polypropylene surfaces. Sulfonation at high temperatures and long time periods however, cause the partial breakdown of the polymer by degradation. Noticeable color change due to the degradation and carbonization of the polypropylene films sulfonated at high temperature and long time were supported by the UV-Vis spectra of the samples. Mechanical properties of sulfonated PP films were investigated. Consequently, after the sulfonation process the mechanical properties of the PP films showed a general trend of decrease with sulfonation time for a given temperature and a very fast decrease at high temperature of sulfonation. Thermal characteristics were found by differential scanning calorimeter (DSC). Thermal analysis revealed that sulfonated PP film samples displayed an additional endothermic peak. The physical effects of the sulfonation were examined by scanning electron microscopy (SEM) which showed a hexagonal hole formations due to the bursting of the air bubbles within the PP films by the effect sulfonation. The lamelae formations were also seen around these holes.

Thesis (Ph. D.)--University of Washington, 2004. / Vita. Includes bibliographical references (leaves 173-205).

By defined structuring of sliding surfaces at dynamic contact seals friction and leakage can be reduced. Compared to macro-structures, micro-structures have the advantage of a quasi-homogeneous influence on the fluid behavior in the sealing gap. The development of suitable microstructures based on prototypes, whose properties are studied on the test bench, is very expensive and time-consuming due to the challenging manufacturing process and measuring technologies, which are necessary to investigate the complex rheological behavior within the sealing gap. A simulation-based development of microstructured sealing surfaces offers a cost- and time-saving alternative. This paper presents a method for simulative design and optimization of microstructured sealing surfaces at the example of a microstructured mechanical face seal.

<p>The purpose of this thesis was to study the influence of manufacturing variations on gear performance. The manufacturing variations inherent in different manufacturing methods were studied to include the effect of real surfaces. Real surfaces have surface irregularities at least on some scale, which can significantly influence how loads are transmitted at the gear contact. To some extent, the lubricant design can help to prevent contact that could lead to tooth failures by forming a protective surface boundary layer. An experimental study was used to consider the compositions of these layers with a surface analysis method.</p><p>In Paper <strong>A</strong> a robust design approach was used to find out to what extent the current standard for calculation of surface durability treats manufacturing variations and the choice of lubricant. The results show that the simplest calculation method used is not enough to predict the effect of these on surface durability. Additionally, the standard quality levels are poorly incorporated in the standard calculating procedures for surface durability, and the quality of the gear tooth is restricted to include only a few parameters.</p><p>In Paper <strong>B</strong> a pin-on-disc machine was used to evaluate the tribofilm formation by the additives and the corresponding wear occurring in the boundary lubrication regime in environmentally adapted lubricants. Studies of the additive and base fluid interaction were carried out using glow discharge-optical emission spectroscopy. It was found that the chemically reacted surface boundary layers played an important role in terms of wear. More specifically, the oxide layer thickness had significant influence on wear. The findings also demonstrate the complexity of lubrication design formulations coupled to these layers. For example, it was found that the pre-existing surface boundary layer (before any lubricant had been added) played an important role in allowing the lubricant to react properly with the surfaces.</p><p>The aim of Paper <strong>C</strong> was to contribute to the knowledge of how different surface topographies, tied to manufacturing methods, influence the early life contact conditions in gears. Topographical measurements of differently manufactured tooth flanks were used as data input to a contact analysis program. The variation in surface topography inherent in the manufacturing method was found to have a strong influence on the contact area ratio.</p>

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