Tesis sobre el tema "Interactions de surface"
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1
Roach, Paul. "Measurement of surface-protein interactions on novel surfaces". Thesis, Nottingham Trent University, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.431900.
Resumen
This thesis is concerned with the fundamental principles affecting protein adsorption. The effects of surface chemistry and topography on protein adsorption characteristics have been identified and quantified. Particular attention has been made to understand how the conformation of surface-bound proteins was affected by the surface onto which they adsorbed. Quartz crystal microbalance (QCM), UV-Vis spectroscopy and fluorometry were used to assess protein-surface affinity and amounts of protein adsorbed at surface saturation levels. Infrared spectroscopy was used to quantify protein conformational changes incurred upon adsorption. A fluorescent assay protocol was developed for use as an external calibration method for the quantification of adsorbed protein an d the results obtained were compared with QCM and an amido black protein assay of the same systems. Model experiments were performed using bovine fibrinogen (an elongated molecule) and albumin (a globular molecule) adsorbing onto flat hydrophilic (OH terminated) and hydrophobic (CH3 terminated) surfaces in the first instance, but later superhydrophilic and superhydrophobic surfaces were also studied. Surface curvature on the nano-scale was used to model topography, wherein protein molecules adsorbed onto spherical substrates (15-165 nm diameter) having chemically defined surfaces. Results obtained indicate that both proteins exhibit a less organised secondary structure upon adsorption onto hydrophobic compared to hydrophilic surfaces, with this effect being greatest for albumin. Adsorption rates and binding affinities were found to be higher on hydrophobic surfaces although the amounts adsorbed at saturation were lower. Supporting spectroscopic data suggests that proteins undergo surface induced deformation upon adsorption. Topography was shown to compound the effects of surface chemistry, with fibrinogen being more denatured on surfaces presenting high surface curvature whereas albumin was more denatured on larger substrates. These effects are most probably due to the differing size and shape of the proteins investigated. This study highlights the possibility of using tailor-made surfaces to influence binding rates and the conformation of bound proteins through protein-surface interactions. The data presented in this thesis demonstrates our ability to control protein adsorption characteristics through careful consideration of the underlying surface, which may facilitate the development and fabrication of materials / surface coatings with tailored bioactivity.
2
Severn, Kathryn A. "Science of synthetic turf surfaces : player-surface interactions". Thesis, Loughborough University, 2010. https://dspace.lboro.ac.uk/2134/7216.
Resumen
This research project has investigated the mechanical properties and behaviour of third generation synthetic turf surfaces used for football and rugby, with a focus on the traction behaviour produced at the shoe-surface interface. The physical characteristics and mechanical properties of the component materials used in the construction of third generation surfaces were examined. The bulk density of the rubber infill material was found to be a key variable. This was shown to be influenced by compaction and the resulting compression of the rubber infill material under an applied load. Increasing the compactive effort and/or compression under loading increased the bulk density. Shear strength of the rubber infill material was shown to be influenced by bulk density, increasing with a higher bulk density. The composite surface system behaviour of third generation synthetic turf surfaces was investigated. Several surface variables were measured including; shockpad thickness, synthetic turf carpet construction, infill thickness, infill bulk density and infill material type. Shockpad thickness, rubber infill thickness and bulk density were found to influence the impact behaviour, with a thicker rubber layer (shockpad and/or rubber infill layer) reducing the hardness of a surface system. Increasing the bulk density of the rubber infill with compactive effort increased the surface system hardness. Traction behaviour of composite surface systems was explored using three traction test methods to measure both rotational and translational traction. Rubber infill bulk density was shown to be a primary influencing variable from the playing surface variables investigated. Several further traction variables were explored to provide a fuller understanding of the mechanisms involved in the production of traction at the shoe-surface interface including; vertical stress, stud configuration, stud dimension, stud penetration, water and temperature. Vertical stress and stud configuration were found to be primary variables influencing traction development. A traction framework has been developed identifying the factors affecting the production of traction at the shoe-surface interface. It is intended that the traction framework can be used by the sports surface industry, sports governing bodies and academia to aid in the decisions and judgements made during the design, construction and maintenance of these surfaces to obtain desired characteristics and optimise performance and safety.
3
Zidan, M. D. "Gas-liquid surface interactions". Thesis, University of Sussex, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333478.
4
Hessey, Stephen. "Surface interactions of ionic liquids". Thesis, University of Nottingham, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.664318.
Resumen
This thesis presents an investigation into the interactions between IL surfaces and gases through studying the kinetics of absorption, adsorption and desorption. A model for absorption is presented in which a gaseous molecule that impacts the surface first enters a physisorbed state, from which it can either desorb or be absorbed into the bulk IL.
5
Cotton, Ross Thomas. "Surface interactions of soccer balls". Thesis, Loughborough University, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.536210.
6
Mouncey, Simon Patrick. "Low energy ion-surface interactions". Thesis, Queen's University Belfast, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333823.
7
Subedi, Laxmi P. "AFM Tip-Graphene-Surface Interactions". University of Akron / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=akron1291144388.
8
Clowes, Steven Kenneth. "Experimental studies of surface-adsorbate interactions and surface magnetism". Thesis, University of York, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323531.
9
Ye, Zhou. "Effect of Nanoscale Surface Structures on Microbe-Surface Interactions". Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/85387.
Resumen
Bacteria in nature predominantly grow as biofilms on living and non-living surfaces. The development of biofilms on non-living surfaces is significantly affected by the surface micro/nano topography. The main goal of this dissertation is to study the interaction between microorganisms and nanopatterned surfaces. In order to engineer the surface with well-defined and repeatable nanoscale structures, a new, versatile and scalable nanofabrication method, termed Spun-Wrapped Aligned Nanofiber lithography (SWAN lithography) was developed. This technique enables high throughput fabrication of micro/nano-scale structures on planar and highly non-planar 3D objects with lateral feature size ranging from sub-50 nm to a few microns, which is difficult to achieve by any other method at present. This nanolithography technique was then utilized to fabricate nanostructured electrode surfaces to investigate the role of surface nanostructure size (i.e. 115 nm and 300 nm high) in current production of microbial fuel cells (MFCs). Through comparing the S. oneidensis attachment density and current density (normalized by surface area), we demonstrated the effect of the surface feature size which is independent of the effect on the surface area. In order to better understand the mechanism of microorganism adhesion on nanostructured surfaces, we developed a biophysical model that calculates the total energy of adhered cells as a function of nanostructure size and spacing. Using this model, we predict the attachment density trend for Candida albicans on nanofiber-textured surfaces. The model can be applied at the population level to design surface nanostructures that reduce cell attachment on medical catheters. The biophysical model was also utilized to study the motion of a single Candida albicans yeast cell and to identify the optimal attachment location on nanofiber coated surfaces, thus leading to a better understanding of the cell-substrate interaction upon attachment.Ph. D.
10
GALAL, TAREK. "Interactions ondes electromagnetiques et surfaces rugueuses : applications a la surface cutanee". Besançon, 1989. http://www.theses.fr/1989BESA2007.
Resumen
Solution analytique de la dispersion d'une onde electromagnetique par une surface rugueuse, prenant en compte les parametres locaux de la topographie=une autre technique est developpee basee sur l'utilisation d'elements finis ou de differences finies
11
Wright, Kierra D. "Chiral polymer surface-cell interaction: understanding the role of chirality & surface topography on polymer-cell interactions". DigitalCommons@Robert W. Woodruff Library, Atlanta University Center, 2012. http://digitalcommons.auctr.edu/dissertations/436.
Resumen
Understanding surface-cell interactions is essential to fabricating a successful biomaterial. In vivo, cells interact with asymmetric features on the micro- and nanoscale. Some of these features, described as valleys, ridges, and spheres, are random, but methodically placed. There are many techniques used to duplicate the topographical features that cells encounter, many of which rely on precision and are labor intensive. Alternatively, the synthetic poly(2-methoxystyrene) (P2MS) homopolymer selfassembled into desirable features, was easily processed and produced the random surface preferred by cells. The features achieved with P2MS were the result of secondary and tertiary conformations confirmed by circular dichroism. The features were also a consequence of the optical activity revealed by polarimetry. Advanced microscopy verified that the features were indeed biomimetic and measured between 150—600 nm in depth and height. Polymers were synthesized using free radical and anionic techniques; some involved the use of a chiral initiator. Spin-casting and solvent annealing were employed to create polymer films for substrate-cell studies. Reaction conditions and molecular weight were varied to achieve different topographical features and thermal profiles. In showing that the films were able to be sterilized, the films were further subjected to cytotoxicity studies involving both Escherichia coli and Bacillus cereus. The results of turbidity measurements and colony counting revealed increased cell viability. The gram positive bacteria, B. cereus, showed increased adhesion through hydrophobic interactions, the same type of interactions proteins rely on for deposition prior to cell adhesion. The cell adhesion study used the human epithelial carcinoma (HeLa) cell line, and showed increased adhesion on chiral initiated P2MS. As a result, this work verified that topographical features can influence cell behavior without the presence of biochemical cues and that P2MS may provide a viable option for tissue engineering applications.
12
Katuri, Jaideep. "Guiding active particles through surface interactions". Doctoral thesis, Universitat de Barcelona, 2018. http://hdl.handle.net/10803/663989.
Resumen
Living organisms and systems are continually converting energy, either internally stored or transduced from their surroundings, into motion. This activity and the resulting self-propulsion constantly push these biological systems out of thermal equilibrium. A number of exotic phenomenon result from the intrinsic non-equilibrium nature of these living systems, that are not accessible in a system at thermal equilibrium. In recent years, these ubiquitous non-equilibrium systems have come to be classified as active matter. Active matter, by definition, refers to systems composed of active units, each capable of converting ambient or stored energy into systematic movement. Examples range from the sub-micrometer scale, with microtubules associated with motor proteins in the cytoplasm, to the micrometer length scales of swimming bacteria, and the meter-length scales of greater familiarity, such as that of fish and birds.
There are two common themes that run through all these active matter systems. The first is the emergence of correlated collective phenomenon through particle-particle interactions as exemplified in flocking of birds, swarming of bacteria and crystallization of self-propelled particles. And the second is the ability of the active units to interact with their surroundings through self-propulsion. Common examples of this include chemotaxis and rheotaxis, observed in many biological systems. In this thesis, I have focussed on studying the ability of artificial active matter systems to respond to their local environment.
As a model active matter system, we use colloidal active particles, that propel due to self-diffusiophoresis. These particles coated with two different materials on each half are referred to as Janus particles. In a solution of H2O2, one of the sides has catalytic properties (Pt), while the other half remains inert (SiO2). This creates a concentration gradient of the reaction product along the surface of the particle and induces a phoretic slip, which propels the particle. We study the dynamics of these self-phoretic particles close to solid surfaces. The particles interact with their surroundings via hydrodynamic and phoretic effects and we observe that when confined closed to a surface, a strong alignment interaction comes into play. This effect can be used to guide micron sized active particles along predetermined pathways. We then exploit this alignment interaction to design micropatterned ratchets capable of generating a strong directional flow of active particles. A different geometry of the same system can also be used to accumulate active particles in confined areas. Finally, we study the influence of an applied external shear flow on the dynamics of active particles near surfaces. We find that a strong directional response emerges for the active particles in the direction perpendicular to the flow direction leading to the cross-stream migration of active particles. This response is dependent on the applied shear flow and the propulsion velocity of the particle, potentially opening up a possibility to sort particles of different activities based on their response to shear flows. Overall, our results indicate that active particles can have a strong directional response in certain environments allowing us to engineer ways of guiding them.Los organismos y sistemas vivos convierten energía almacenada internamente o derivada de sus alrededores en movimiento de forma continua. Esta actividad puede causar una constante auto-propulsión que lleva a estos sistemas a un estado fuera de equilibrio térmico. Gracias a esto, aparecen un gran número de fenómenos exóticos que no son accesibles para un sistema que se encuentra en equilibrio térmico. En los últimos años se ha clasificado a estos sistemas de no equilibro como “material activa”. La materia activa, por definición, incluye los sistemas compuestos de unidades activas, cada una de ellas capaz de convertir la energía almacenada o del entorno en movimiento sistemático. Existen varios ejemplos que van desde la escala sub-micrométrica, donde podemos encontrar a los microtúbulos asociados a proteínas motoras en el citoplasma, a las grandes escalas, donde se encuentran sistemas más familiares como peces o pájaros, pasando por la escala micrométrica, donde nadan las bacterias. Podemos diferenciar dos temas principales que se manifiestan en todos estos sistemas de materia activa. El primero es la aparición de fenómenos colectivos correlacionados a través de interacciones partícula-partícula, como ocurre en bandadas de pájaros, enjambres bacterianos y la cristalización de partículas auto-propulsadas. El segundo es la capacidad de estas unidades activas de interaccionar con sus alrededores a través del fenómeno de la auto-propulsión, por ejemplo, a través de quimiotaxia o reotaxia, como se puede observar en muchos sistemas biológicos y que ya han sido reportados en varios estudios. En esta tesis, me he enfocado en el estudio de este último tema principal: la interacción de partículas activas con su entorno local. Como modelo de sistema de materia activa, usamos partículas activas coloidales que se propulsan gracias al fenómeno de auto-difusioforesis. Estas partículas están recubiertas por dos materiales diferentes en cada una de sus caras, y son comúnmente llamadas “partículas Janus”. Una de sus caras está recubierta con Pt, material que cataliza la descomposición de H2O2, mientras que la otra cara está recubierta de un material inerte (SiO2). En una solución de H2O2, la reacción que ocurre en la parte catalítica produce un gradiente de concentración de producto a lo largo de la superficie de la partícula e induce un deslizamiento forético que la propulsa. En esta tesis se ha estudiado la dinámica de estas partículas "autoforéticas" cerca de superficies sólidas. De manera natural, las partículas interaccionan con su alrededor debido a los efectos foréticos e hidrodinámicos. Cuando estas partículas se hayan confinadas cerca de una superficie, observamos que se origina en ellas una fuerte interacción de alineamiento. A partir de ello, consideramos interesante diseñar ratchets micro estampados capaces de generar un flujo direccional de partículas activas. Por otra parte, estudiamos la influencia de aplicar un flujo de cizalla externo en la dinámica de las partículas activas cerca de superficies. A consecuencia del flujo externo, encontramos que en el sistema emerge una respuesta fuertemente direccional para las partículas activas en la dirección perpendicular al flujo provocando una migración "cross-stream" de partículas activas.
13
Thom, Alasdair D. "Analysis of vortex-lifting surface interactions". Thesis, University of Glasgow, 2011. http://theses.gla.ac.uk/3037/.
Resumen
The interaction of a vortex with a lifting surface occurs in many aerodynamic systems, and can induce significant airloads and radiate impulsive noise. Yet due to their complex nature, the ability to accurately model the important flow physics and noise radiation characteristics of these interactions in realistic situations has remained elusive. This work examines two cases of vortex-lifting surface interactions by enhancing the capabilities of a high fidelity flow solver. This flow solver utilises high spatial discretisation accuracy with a 5th order accurate WENO scheme, and overset meshes to accurately resolve the formation, evolution and interaction of a tip vortex using an inviscid approximation of the fluid. An existing computational infrastructure is further developed and applied to analyse blade-vortex interactions that occur on a helicopter rotor. An idealised interaction is studied, where an independently generated vortex interacts with a rotor. It is found that through the employment of adequate spatial and temporal resolution, the current methodology is capable of resolving the important details of the interaction over a range of vortex-blade miss distances. A careful study of the spatial and temporal resolution requirements is conducted to ensure that the computed results converge to the correct physical solution. It is also demonstrated that a linear acoustic analysis can accurately predict the acoustic energy propagated from these interactions to the far-field, provided the blade surface pressures are accurately computed. The methodology is then used to study an idealised propeller wake-wing interaction, which occur behind a tractor mounted turboprop. A computationally efficient method of modelling the wake-wing interaction is developed and the computed surface pressures of the interaction are confirmed to agree well with the experimental data. The analysis is coupled to an optimisation algorithm to determine a novel wing design, and it is found that significant drag reductions can be achieved with small changes in the twist distribution of the wing. This work confirms that by using a combination of strategies including efficient grids, high order accurate numerical discretisations and a flexible software infrastructure, high fidelity methods can indeed be used to accurately resolve practical cases of vortex-lifting surface interactions in detail while being feasible in a design setting. The airloads and aeroacoustics from these interactions can be accurately predicted, thus confirming that with the modern advances in computing and algorithms, high fidelity methodologies such as those presented in this thesis are in a position to be used to gain a deep understanding of the relevant flow physics and noise radiation patterns, and their impact on aircraft design.
14
Driscoll, Heather Frances. "Understanding shoe-surface interactions in football". Thesis, Sheffield Hallam University, 2012. http://shura.shu.ac.uk/17145/.
Resumen
One of the key aims of modern football shoe manufacturers is to find the balance between developing a shoe that improves performance but also minimises the risk of injury. Traction properties of the outsole play an important part in reaching this balance; high levels of traction are necessary to enable players to accelerate and change direction without slipping, but excessive traction can lead to stud fixation, a potential cause of injuries. The ability to accurately measure and assess the traction properties is essential in the design of outsoles, but appropriate test parameters need to be used in order for the assessment to relate back to the intended use. The purpose of the study was to develop a method to identify how the shoe interacts with the surface during realistic football movements and then to use observations from data collected to recommend appropriate test parameters. A high-speed camera system was developed to capture the motion of the shoe in both a laboratory and natural turf environment. The cameras were calibrated using the checkerboard approach and filmed at 1000 Hz. Five markers positioned on the side of the shoe were tracked using a semi-automated algorithm developed using image processing techniques. Transposition matrices were used to identify the location of individual studs on the outsole of the shoe enabling the orientation, velocity and acceleration of the shoe to be calculated. Two data collection studies took place; firstly a single-participant study in the laboratory using a force-plate to relate kinematic results to kinetic information and secondly, a larger scale data collection outside on natural turf. Three movements representing scenarios requiring high levels of traction in football were assessed; acceleration, change in direction and braking. A representative trial for each movement was selected and full post-processing analysis was carried out. Information such as the orientation of the shoe on foot-strike, translation directions and centre of rotations during the transition phase and the number of studs in contact with the surface during push-off was obtained for each movement. The period at which the player was at greatest risk of slipping was identified for each movement. The motion of the shoe during this period was used to suggest appropriate test conditions for mechanical and computational traction testing methods. The influence of the shoe-surface interaction on outsole design was also considered; with the observed translation directions and centre of rotations being used to suggest a design aiming to enhance translational traction, but minimise rotational resistance.
15
Kerford, M. "Modelling of energetic molecule-surface interactions". Thesis, University of Surrey, 2000. http://epubs.surrey.ac.uk/843052/.
Resumen
This thesis contains the results of molecular dynamics simulations of molecule-surface interactions, looking particularly at fullerene molecules and carbon surfaces. Energetic impacts of fullerene molecules on graphite create defect craters. The relationship between the parameters of the impacting molecule and the parameters of the crater are examined and found to be a function of the energy and velocity of the impacting molecule. Less energetic fullerene molecules can be scattered from a graphite surface and the partitioning of energy after a scattering event is investigated. It is found that a large fraction of the kinetic energy retained after impact is translational energy, with a small fraction of rotational energy and a number of vibrational modes. At impact energies where the surface is not broken and at normal incidence, surface waves are seen to occur. These waves are used to develop a method of desorbing molecules from a graphite surface without damage to either the surface or the molecules being desorbed. A number of fullerene molecules are investigated and ways to increase the desorption yield are examined. It is found that this is a successful technique for desorbing large numbers of intact molecules from graphite. This technique could be used for desorbing intact molecules into a gas phase for mass spectrometric analysis.
16
Tidwell, Caren Diana. "Endothelial cell interactions with model surfaces : effect of surface chemistry, surface mobility, and the adsorbed protein layer /". Thesis, Connect to this title online; UW restricted, 1999. http://hdl.handle.net/1773/8004.
17
Walliser, André. "Caractérisation des interactions liquide-fibre élementaire par mouillage". Mulhouse, 1992. http://www.theses.fr/1992MULH0248.
Resumen
Un système expérimental, Microwetting (marque Du Pont de Nemours), a été développé dans le but de déterminer, localement et avec précision, l'énergie de surface de fibres élémentaires par mouillage. Un faible volume de liquide est mis en contact avec une fibre en un endroit sélectionné de la surface. En l'absence d'étalement spontané, se forme alors une goutte de liquide qui adopte une conformation soit axisymétrique soit non-axisymétrique par rapport à l'axe de la fibre. Dans le premier cas, l'angle de contact entre la goutte et la fibre est calculé grâce à une équation qui relie l'angle au diamètre de la fibre, à la longueur et au diamètre de la goutte. Dans le cas d'une conformation non-axisymétrique, nous avons établi un modèle fondé sur la projection mathématique, aux volumes de gouttes nuls, des variations de paramètres géométriques de la goutte. Ce modèle conduit à la détermination de l'angle de contact représentatif des interactions à l'interface. Ainsi les mesures par mouillage sur fibres élémentaires permettent le calcul des composantes dispersive et non-dispersive de l'énergie superficielle quelles que soient les manifestations macroscopiques des interactions solide-liquide
18
Payne, Timothy Ernest Civil & Environmental Engineering Faculty of Engineering UNSW. "URANIUM (VI) INTERACTIONS WITH MINERAL SURFACES: CONTROLLING FACTORS AND SURFACE COMPLEXATION MODELLING". Awarded by:University of New South Wales. School of Civil and Environmental Engineering, 1999. http://handle.unsw.edu.au/1959.4/17482.
Resumen
The objective of the work described in this thesis was to improve the scientific basis for modelling the migration of U in the sub-surface environment. The project involved: ?? studying the sorption of U on model minerals (Georgia kaolinite and ferrihydrite) in laboratory experiments ?? carrying out experimental studies of U sorption on complex natural substrates ?? studying the mechanisms influencing U retardation in the natural environment, including transformation processes of iron oxides ?? identifying chemical factors which control U sorption on model and natural substrates ?? developing a mechanistic model for U sorption on ferrihydrite and kaolinite using the surface complexation adsorption model , and ?? assessing and modelling the effect of complexing ligands on uranyl adsorption. Uranium (VI) sorption on geological materials is influenced by a large number of factors including: pH, ionic strength, partial pressure of CO2, adsorbent loading, total amount of U present, and the presence of inorganic and organic ligands. The sorption of UO22+ typically increases with increasing pH (the 'low pH sorption edge') up to about pH 7. In systems equilibrated with air, there is a sharp decrease in sorption above this pH value (the 'high pH edge'), due to strong complexation between uranyl and carbonate. The adsorption model being used for ferrihydrite is a surface complexation model with a diffuse double layer, and both strong and weak sites for U sorption. Based on the analysis of EXAFS data, the U surface complexes were modelled as mononuclear bidentate surface complexes of the form (>FeO2)UO20. Ternary surface complexes involving carbonate with the form (>FeO2)UO2CO32- were also required for the best simulation of U sorption data. There was a slight decrease in U sorption on ferrihydrite in systems that contained sulfate. It was necessary to consider competition between UO22+ and SO42- for surface sites, as well as complexation between UO22+ and SO42- to model the data. The presence of citrate considerably reduced U sorption and caused dissolution of ferrihydrite. Complexation of citrate with both uranyl and ferric ions was taken into account in modelling this system. The model required the optimisation of the formation constant for a postulated mixed metal (U/Fe/citrate) aqueous complex. Humic acid increased U uptake at pH values below 7, with little effect at higher pH values. In terms of the amount of U sorbed per gram of adsorbent, U uptake on kaolinites KGa-1 and KGa-1B was much weaker than U uptake on ferrihydrite under similar experimental conditions. Electron microscope examination showed that titanium-rich impurity phases played a major role in the sorption of U by these standard kaolinites. A relatively simple model for uranyl sorption on the model kaolinites was able to account for U sorption under a wide range of experimental conditions. The model involved only three surface reactions on two sites (>TiOH and >AlOH), with a non-electrostatic surface complexation model. The relative amounts of the sites were estimated from AEM results. Precipitation was taken into account in modelling the experimental data obtained with high U concentrations. The effects of sulfate and citrate on U sorption by kaolinite were also assessed and modelled. Sulfate had a small effect on U sorption, which may be explained by aqueous complexation. Citrate had a greater effect, and this was not wholly explained by the formation of aqueous U-citrate complexes. The most likely explanation would also involve competition for surface sites between U and citrate. Uranyl uptake on ferrihydrite was greatly increased by the presence of phosphate. This was not due to precipitation, and was attributed to the formation of a ternary surface complex with a proposed structure of (>FeO2)UO2PO43-. The log K value for the formation of this complex was optimised using FITEQL. Phosphate also increased uptake of uranyl on kaolinite, and this was also attributed to the formation of ternary uranyl phosphate surface species. Uranium sorption on weathered schist samples from the vicinity of the Koongarra U deposit in northern Australia was generally similar to the model minerals (in terms of the effects of pH, ionic strength, total U, etc). Many experiments with the natural materials were spiked with an artificial U isotope (236U), which allowed adsorption (of 236U) and desorption (of 238U) to be distinguished, and provided a means of estimating the 'labile' or 'accessible' portion of the natural U content. A significant advantage of this method is that (unlike chemical extractions) it does not rely on the assumptions about the phases extracted by 'selective' reagents. Uranium sorption experiments were also carried out with Koongarra samples which had been treated with citrate / dithionite / bicarbonate (CDB) reagent to remove iron oxides. Uranium sorption was greatly decreased by the CDB extraction, which reduced the surface area of the samples by about 30-40%. To further elucidate the impact of iron minerals on U mobility in the natural environment, the transformation of synthetic ferrihydrite containing adsorbed natural uranium was studied. In these experiments, the ferrihydrite was partially converted to crystalline forms such as hematite and goethite. The uptake of an artificial uranium isotope (236U) and the leaching of 238U from the samples were then studied in adsorption / desorption experiments. The transformation of ferrihydrite to crystalline minerals substantially reduced the ability of the samples to adsorb 236U from solution. Some of the previously adsorbed 238U was irreversibly incorporated within the mineral structure during the transformation process. Therefore, transformation of iron minerals from amorphous to crystalline forms provides a possible mechanism for uranium immobilisation in the groundwater environment. In considering the overall effect on U migration, this must be balanced against the reduced ability of the transformed iron oxide to adsorb U. The experiments with the model and natural substrates demonstrated that trace impurities (such as Ti-oxides) and mineral coatings (such as ferrihydrite) can play a dominant role in U adsorption in both environmental and model systems. Although the various substrates had different affinities for adsorbing U, the effects of chemical factors, including pH, ionic strength, and carbonate complexation were similar for the different materials. This suggests that a mechanistic model for U sorption on model minerals may eventually be incorporated in geochemical transport models, and used to describe U sorption in the natural environment.
19
Daff, Thomas Duncan. "Copper at the nanoscale : computational studies of clusters, surfaces and surface interactions". Thesis, Birkbeck (University of London), 2010. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.725638.
Resumen
Size, shape and structure control of copper nanoparticles has been achieved through chemical synthesis methods, although only at an empirical level. An understanding of the processes involved at the molecular level will enable a finer control over the particles that are produced. Using interatomic potential methods, the (111) surface of copper is demonstrated to be the most stable both in the ground state, and with respect to surface melting. The addition of low-coordinated sites initiates melting at lower temperatures, although the terraces remain stable. The most stable particle shapes, whilst fairly spherical, still show a dominance of (111) faces. The growth modifying properties of hydrazine, the reducing agent, are modelled by surface adsorption using ab initio methods. Gas phase adsorption shows stronger binding to the (100) surface than the (111) surface. The strongest adsorptions are on the (110) surface, where the rougher structure accommodates bridging geometries, and low-coordinated adatoms provide sites for stronger adsorption on the planar surfaces. Dissociation of the molecule is thermodynamically favoured. The gas phase studies do not fully explain the synthesis. Instead, explicit treatment of the hydration shell with first-principles dynamics simulations predicts adsorption on the (111) surface, but not on the (100) surface. The preferential binding provides a consistent rationalisation of the experimental method.
20
Nayakasinghe, Mindika Tilan Abeyrathna. "Fundamental Surface Properties and Gas-Surface Interactions of Two-Dimensional Materials". Diss., North Dakota State University, 2019. https://hdl.handle.net/10365/29325.
Resumen
Heterogeneous model catalysis with supported nanomaterials on ultra-thin two-dimensional films has contributed significantly to improve the existing industrial catalytic processes, as well as to discover novel ways to enhance selectivity, specificity, and stability of the catalysts. Silica and zeolites are of particular interest, which has been widely utilized as catalysts and catalytic supports in several industrial processes. However, there are a limited number of surface science studies with zeolites due to the lack of surface analogs. Understanding the fundamental surface properties of silica and zeolites, involving the synthesis of surface analogs of silica and zeolites, characterization, surface modification, and screening for chemical and physical properties connected to the heterogeneous catalysis related applications utilizing advanced ultra-high vacuum-based surface science techniques is the main focus of this dissertation. Catalyst particles should be finely distributed on high surface area supports, in order to have high selectivity and specificity. Particle agglomeration during extreme catalyst operation (reaction) conditions decreases the efficiency of the catalysts over time. One common strategy to address the issue of particle agglomeration is to promote strong catalyst-support interactions. In this study, chemical reactivity of the inert silica was improved by doping with aluminum, which enhanced the polarity of silica (2D-zeolites) and hence the catalyst-support interactions compared to inert silica. Organohalide perovskite thin films are a fascinating class of material, which attract much attention in the recent past as the light harvesting materials in solar cells due to excellent power conversion efficiencies. However, poor thermal, chemical, and long-term stability limit the industrial applications of these organohalide perovskites. Gas-surface interactions on methylammonium lead iodide perovskite thin films were investigated in order to understand the thermal and the chemical degradation mechanisms utilizing UHV-based surface analytical techniques combined with computational calculations. Thermal stability improvement of the perovskite thin films by surface passivation using a protective chemical inhibition layer was successfully investigated experimentally.ACS-PRF
North Dakota State University. Department of Chemistry and Biochemistry
North Dakota State University. Research and Creative Activity
21
Daniel, Richard Crosson. "Ink-media interactions in ink-jet printing /". Thesis, Connect to this title online; UW restricted, 2004. http://hdl.handle.net/1773/9829.
22
Frühauf, Jens. "Surface dopant interactions in ultra-shallow junctions". [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=979061350.
23
Jarvis, Suzanne Philippa. "Atomic force microscopy and tip-surface interactions". Thesis, University of Oxford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359441.
24
Kolasinski, Robert David Goodwin David G. "Fundamental ion-surface interactions in plasma thrusters /". Diss., Pasadena, Calif. : California Institute of Technology, 2007. http://resolver.caltech.edu/CaltechETD:etd-11222006-105854.
25
Oliveira, Marta Isabel Abreu. "Molecular interactions at the T cell surface". Tese, Instituto de Ciências Biomédicas Abel Salazar, 2007. http://hdl.handle.net/10216/7220.
26
Willems, Nathalie. "Molecular dynamics simulations of lipase-surface interactions". Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:7765c334-7c02-4190-a4b2-99ad315cfe52.
Resumen
Lipases are enzymes that play fundamental roles in fat digestion and metabolism, and function at the interface formed between hydrophobic molecules and the surrounding aqueous environment. These interfacial interactions are thought to induce conformational changes in a "lid" region of the lipase, leading to a dramatic increase in activity. This thesis aims to provide insight into the interactions that govern lipase association with interfaces of di erent structural characteristics, and the possible conformational changes that arise as a function of these interactions. A multi-scale molecular simulation approach (combining atomistic and coarse-grained methods) was applied to study two different lipases with a range of interfaces, including "soft" biological surfaces and "hard" non-biological surfaces. Three major insights were gained from these studies. First, interactions of a small bacterial lipase (M37) with lipid interfaces resulted in substantial structural changes in a lid region, uncovering of the underlying active site. A mechanism of interfacial ac- tivation is proposed for this lipase. Second, the interaction of M37 with non-biological interfaces di er from lipid interfaces, leading to altered interfacial orientations with possible functional consequences. Third, the amino acid composition of the lid region of a yeast lipase (TLL) is shown to play crucial roles in lipase activation and structural stability.
27
Agbormbai, Adolf Akombi. "Gas surface interactions in rarefied hypersonic flows". Thesis, Imperial College London, 1988. http://hdl.handle.net/10044/1/46929.
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Ioannou, Marina. "Cell surface interactions of Coxsackie A9 virus". Thesis, University of Essex, 2018. http://repository.essex.ac.uk/22325/.
Resumen
An understanding of how viruses interact with their receptors is vital as this step is a major determinant of host susceptibility and disease. Coxsackievirus A9 (CAV9), an enterovirus, harbours an integrin- recognition motif, RGD (Arg-Gly-Asp), in the capsid protein VP1 and although modes of transmission and pathogenesis are still largely unknown, this motif is believed to be primarily responsible for integrins αvβ6 and αvβ3 binding. The conservation of the RGD +1 position in CAV9 and other picornaviruses showed evidence that this is related to viral tropism and infectiousness of the virus. CAV9 has also been reported to interact with the heparan sulphate/heparin class of proteoglycans (HSPG). This thesis describes work designed to improve our understanding of the involvement of a) the RGD motif and more specifically the RGDX position in CAV9 infection, using a large panel of different RGDX variants and a number of cell lines not previously used in CAV9 research b) the significance of possible interactions between CAV9 and HSPG in infection. Several CAV9 variants were tested in a panel of 8 different cell lines. Infection in each cell line was observed to follow either an RGD- dependant or RGD- independent pathway, although the results did not fully correlate with the receptor expression found on the cell lines used. The RGDX position was found to be critical for efficient infection in cells when an RGD- dependent pathway is used. To understand which integrin is likely to be involved in entry, into one of the RGD-dependent cell lines, A549, blocking antibodies against αvβ3 and αvβ6 were used. Neither antibody gave full protection against CAV9, as has been reported previously, suggesting that other integrins might also be used. Two new HSPG-binding CAV9 mutants were discovered, showing that binding to HSPG can be achieved by several mechanisms. Binding to HSPG was found to be significant in some cells, but not others, again illustrating the complexity of interactions between CAV9 and the cell surface. The results obtained have greatly improved our understanding of how CAV9 infects cells. This will be useful in the design of antivirus drugs and also gives a framework for the modification of CAV9 or other RGD containing picornaviruses for specific targeting of cancer cells for oncolytic therapy.
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Rêgo, Celso Ricardo Caldeira. "Ab-initio studies of adsorbate-surface interactions". Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/76/76131/tde-29012018-093011/.
Resumen
This thesis supplies a contribution to the understanding of the interaction between carboncarbon surfaces, atoms with carbon-surfaces, and atoms with metallic surfaces. It is well established that the surface-surface and atom-surface interactions are interesting, important and challenging for reasons that vary from industrial interest up to the academic necessity of understanding it deeply. Currently, there are many measurements and simulations for the geometric and electronic properties of Graphite, these differ by more than 40%. This implies that our understanding of the nature of this material is quite poor. The interaction between small transition-metals clusters with a Graphene sheet is another example where our knowledge is very limited. There are many theoretical studies in the literature that describe the interaction between these clusters with a Graphene sheet, but they agree and disagree on many points, which calls for systematic study of this issue. In this thesis we will focus our efforts on studying the surface-surface and atom/clusters-surface interactions. This thesis is split into three projects. The first aims to contribute to the understanding of the interlayer interactions of the bulk Graphite. In the second, we intend to shed some light on comprehending the interaction of an adatom with a Graphene sheet. Both of these projects, are studied within DFT framework with the inclusion of the van der Waals (vdW) corrections. In the Graphite project, we found that the electronic and geometric properties depend on the vdW correction employed in the calculation. In the adatom supported on Graphene project, we combined a modified Anderson-Newns model to describe the coupling between the adatom with Graphene. In addition, we found the existence of competition between quantum and classical forces, which determine the type of site in which the adatom prefers to adsorb. The last project is a dynamical study of an atom that impinges upon a metallic surface. In this project, we focus on the calculation of the sticking coefficient, a measure of the amount of nuclear density attached to the metal surface after collision. At this time the project is not one 100% ready, but our preliminary results indicates that, a small part of the nuclear density stays stuck on the metal.Esta tese ajuda a entender as interações entre duas superfícies de carbono. A natureza da interação de átomos ou aglomerados atômicos adsorvidos sobre uma superfície de carbono. Além disso, visa esclarecer a dinâmica de um átomo sendo adsorvido sobre uma superfície metálica. As interações superfície-superfície e átomos-superfícies são importantes por razões que variam desde o interesse industrial até a necessidade acadêmica para compreendê-la profundamente. Entendê-las ainda é um desafio. Diversos trabalhos apresentam medidas experimentais e simulações para as propriedades geométricas e eletrônicas do grafite. Tais medidas diferem em mais ide 40% umas da outra. Isso mostra que nossa compreensão sobre a natureza desse material ainda é bastante pobre. A interação entre pequenos grupos de metais de transição com uma folha de grapheno é outro exemplo em que nosso conhecimento é limitado. Existem muitos estudos teóricos na literatura que descrevem a interação desse tipo de aglomerado com uma folha de grafeno, porém há numerosas discordâncias. Tais controvérsias parecem suplicar por um estudo sistemático. Nesta tese focamos nossos estudos nas interações superfície-superfície e de átomos ou aglomerados atômicos com superfícies de carbono e de um metal. A tese foi dividida em três projetos. O primeiro visa compreender melhor a interação entre as camadas do grafite. No segundo, pretendemos lançar alguma luz no entendimento da interação de átomos e aglomerados atômicos com uma folha de grafeno. Esses dois projetos, são estudados à luz da Teoria do Funcional da Densidade com a inclusão das correções van der Waals (vdW). No Projecto sobre o grafite, mostramos que as propriedades eletrônicas e geométricas dependem do tipo de correção de vdW empregada no cálculo. No projeto sobre átomos e aglomerados atômicos adsorvidos no grapheno, combinamos um modelo modificado de Anderson-Newns para descrever o acoplamento entre um átomo adsorvido e o grafeno. Além disso, encontramos uma competição entre forças quânticas e clássicas, a qual determina o tipo de sítio no qual o átomo prefere ser adsorvido. O último projeto é um estudo dinâmico de um átomo colidindo contra uma superfície metálica. Nesse projeto o foco é posto no cálculo do coeficiente de aderência, o qual mede a taxa de densidade nuclear presa na superfície metálica após a colisão. Resultados preliminares indicam que, uma pequena parte da densidade nuclear permanece aderida ao metal depois da colisão.
30
Usman, Jauhr. "Quantification of affinity mediated cell/surface interactions". Thesis, University of Bath, 1997. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362307.
31
Jones, Cullen Brandon. "Groundwater-Surface Water Interactions near Mosier, Oregon". PDXScholar, 2016. https://pdxscholar.library.pdx.edu/open_access_etds/3414.
Resumen
The town of Mosier, Oregon, is located near the east, dry end of the Columbia River Gorge, and the local area is known for cherry orchards that rely heavily on groundwater for irrigation. The CRBG groundwater system in Mosier has experienced groundwater declines of up to 60 meters due to over-pumping and or commingling. Declining groundwater levels have led to concerns over the sustainability of the resource, as it is the principle water source for irrigation and domestic use. Despite numerous previous studies of groundwater flow in CRBG aquifers here and elsewhere in the Columbia River basin, an aspect that has received relatively little attention is the interaction between groundwater and surface waters at locations where interflow zones are intersected by the surface waters.
The objective of my research is to investigate how CRBG interflow zone exposures in Mosier Creek may be controlling groundwater elevations in the area. The methods used include: (1) geochemical analysis of well cuttings and detailed geologic mapping along area streams to identify interflow zones of individual CRBG flows, (2) analysis of stream discharge data and groundwater elevation data to confirm exchange of groundwater and surface waters, and (3) collection and analyses of 31 water samples from area wells, streams, and springs, to determine if waters from individual CRBG aquifers can be hydrochemically identified and to further constrain understanding of surface and groundwater interactions.
My study confirms that the general elevation of the Pomona Member and Basalt of Lolo interflow zone creek exposure is coincident with the elevation where a change in slope of the decline trend in 2004 is seen in Mosier area well hydrographs. Furthermore, the results of stream discharge data indicated a close connection between drawdown from groundwater pumping during irrigation season and groundwater- surface water interaction. At the time of drawdown in the upper-most CRBG aquifer (Pomona), the stream transitions from gaining to losing water into the groundwater system.
Elemental chemistry data indicates the Frenchman Springs Sentinel Gap aquifer waters are the most evolved waters in this study. Stable isotopic data reinforced this determination as the Sentinel Gap waters are the lightest, or most negative, with regard to δD and δ18O. Sentinel Gap samples were more depleted than other aquifer samples by 4.38 to 6.89 0/100 for δD and 0.39 to 0.59 0/100 for δ18O. The results of the general chemistry and isotope data reveal a more evolved chemical signature in lower watershed groundwater versus a less evolved signature for waters from wells located higher up on the Columbia Hills anticline. This was interpreted to be the result of the major structural features in the area providing for a more regional pathway of recharge in lower watershed groundwaters, versus a more local source of recharge for upper watershed groundwaters. There was also a pronounced commingled signature in the elemental ratios of lower watershed aquifer waters. The suspected mechanism of recharge to lower watershed wells is through younger Cascadian deposits upslope from the local watershed.
The findings of this study reveal the importance of a detailed understanding of CRBG stratigraphy and its relation to surface waters, especially for other areas within the Yakima Fold Belt or Oregon and Washington. Studies that do not consider the influence that individual CRBG flows can have on groundwater-surface water interactions, and the groundwater system as a whole, run the risk of improperly assessing the groundwater resource for a region.
32
Doherty, Kyle George. "Microplasma technology for influencing cell-surface interactions". Thesis, University of Liverpool, 2014. http://livrepository.liverpool.ac.uk/18213/.
Resumen
Cataracts are the most common cause of preventable blindness worldwide. During cataract surgery a polymeric intraocular lens (IOL) is used to replace the cloudy natural lens. The most common post-operative complication is posterior capsule opacification (PCO). PCO is a wound healing response related to scarring, in which cellular changes disrupt the light path to the back of the eye through various processes, requiring a costly surgery to restore vision. The material of the IOL has been shown to affect PCO and it is hypothesised that the surface modification of IOL materials may be able to reduce the incidence of PCO. The use of plasmas established in the field of biomaterials modification and atmospheric pressure processes have significant benefits over the previous low pressure systems. In this work investigates the use of an atmospheric pressure plasma jet to modify the surface properties of polymeric materials, with the aim of developing a surface treatment method for use on IOLs. Materials and Methods The centre of polystyrene (PS) and poly(methyl methacrylate)(PMMA) surfaces were treated with an atmospheric pressure microplasma jet. The modification of surfaces was characterised by spatially resolved water contact angle, x-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). LECs were seeded onto surfaces and grown for 1-7 days. Cell attachment, growth and morphology were examined microscopically. The concentrations of some cytokines implicated in PCO (transforming growth factor-β2, basic fibroblast growth factor, interleukin-1, interleukin-6, and tumour necrosis factor-α) in culture medium were examined at specific time points. Tissue culture polystyrene and untreated materials served as controls. Atmospheric pressure plasma polymerisation of amine containing monomers using a plasma jet was also investigated. Results and Discussions The size of surface treatment could be tailored by altering flow rate and sample-nozzle distance. Surface treatment was due to an increase in surface oxygen content and plasma treatment did not cause a significant change in surface roughness. Plasma treatment increased the LEC adhesion to substrates. LECs were densely populated in the centre of treated materials and cells lacked the cobblestone morphology typical of epithelial cells. The secretion of inflammatory cytokines by LECs grown on plasma treated surfaces did not appear to be up-regulated in comparison to tissue culture polystyrene, however these results are preliminary. This work demonstrated that atmospheric pressure plasma polymerisation can be achieved using the plasma jet system to incorporate nitrogen functionalisation onto PS surfaces; however oxygen was also incorporated onto surfaces. Conclusions This work demonstrates that an atmospheric pressure microplasma jet can be used to modify surfaces in a spatially defined manner, without damaging the polymer surfaces. The increase in surface oxygen promotes cell adhesion which can be confined to an area <3mm. This treatment size is too large to be used to create different spatially defined treatments on IOL optics as the typical optic diameter is only 6mm. The large treatment size is possibly due to gas convection spreading reactive species across the surface of samples when the plasma jet reaches the surface. Plasma polymerisation could possibly be used to incorporate functional groups which promote LEC growth which maintains an epithelial morphology.
33
Fernandez, Nicolas. "Etude des interactions gaz - surface par DFT". Thesis, Aix-Marseille, 2015. http://www.theses.fr/2015AIXM4715/document.
Resumen
Les travaux présentés dans cette thèse relèvent principalement de la réactivité des surfaces et des interactions gaz-surface. Les champs d'application de ce travail sont variés et s'inscrivent principalement dans le domaine de la fusion nucléaire et du projet ITER.Dans ce cadre, la modélisation à l'échelle atomique est un outil important pour comprendre et interpréter les résultats expérimentaux. Notre domaine de compétences est celui du calcul de structures électroniques et des propriétés chimiques. Ces calculs sont principalement conduits dans le cadre de la Théorie de la Fonctionnelle de la Densité (DFT) et de la thermodynamique statistique.Bien que composé de six chapitres, ce manuscrit comporte trois parties principales. La première est dédiée à la présentation des méthodes de calculs utilisées tout au long de cette thèse. La deuxième partie est consacrée à l'étude de la formation du carbure de béryllium à partir d'un dépôt de béryllium sur une surface de graphite. Le degré de fiabilité des résultats DFT a été évalué et les principales étapes de la formation de carbure de béryllium ont été déterminées. La troisième partie développée sur deux chapitres est consacrée à l'étude de l'interaction entre l'hydrogène et le tungstène métallique. La dissolution, la diffusion ainsi que le piégeage de l'hydrogène dans le tungstène ont été étudiés. Un excellent accord a été obtenu entre les valeurs calculées et les résultats expérimentaux de référenceThe work herein presented deals with the reactivity of surfaces and the gas–surface interaction. This work is connected to different fields of applied science and more specifically to the field of nuclear materials for fusion devices like the International Thermonuclear Experimental Reactor (ITER).Numerical simulations at the atomic scale can provide an in depth understanding of the mechanisms at the origin of experimental observations. More specifically, our skills are about electronic structure calculations and chemical properties modelling; most of the work we produced has been conducted within the framework of the Density Functional Theory (DFT) and statistical thermodynamics. While made of six chapters, the manuscript can be cast in three main parts. The first one is dedicated to the methods used throughout this thesis. The second is devoted to the formation of beryllium carbide from deposited beryllium atoms on graphite surfaces; the reliability of the DFT results was benchmarked and the main steps of the beryllium carbide formation were determined. The third part explores the interaction between hydrogen and metallic tungsten. The formation of vacancies in the material, its impact on the solubility and diffusion of hydrogen in tungsten were investigated, and the results were compared with experiment; an excellent agreement was found
34
Di, Fino Alessio. "Comparative approach to barnacle adhesive-surface interactions". Thesis, University of Newcastle upon Tyne, 2015. http://hdl.handle.net/10443/2838.
Resumen
Barnacles are considered to be one of the major marine fouling organisms. Their settlement behaviour has been investigated using mainly Balanus amphitrite as a model organism. To better understand the mechanisms involved during the colonisation of surfaces by cypris larvae we have investigated another species, B. improvisus, which is reported to have different surface preferences compared to B. amphitrite. This study aims to unravel the effects of surface physicochemical cues, in particular surface free energy (SFE), surface charge and elastic modulus on the settlement of cyprids of both species. The use of well-defined surfaces under controlled conditions further facilitates comparison of the results with B. amphitrite. Furthermore, since this phase of presettlement behaviour is characterised by temporary adhesive (footprint) deposition, considered to be fundamental to surface exploration and surface discrimination by cyprids, some of the chemistries used for the settlement assays were used to investigate temporary adhesive-surface interactions. Cyprids were exposed to a series of model surfaces, namely self-assembled monolayers (SAMs) of alkanethiols with varying end-groups, homogenously applied to gold-coated polystyrene Petri dishes. The settlement response was significantly higher on negatively charged SAMs and lower on positively charged surfaces, while intermediate settlement occurred on neutral SAMs. Furthermore, no effects were observed when data were plotted against surface free energy after 48 hr of exposure. Temporary adhesive on SAMs was investigated using imaging ellipsometry and atomic force microscopy. Relatively thick footprints with low wetting were found on positively charged surfaces. Settlement of both species was also low on these surfaces. Footprints were thinner and spread more on hydrophobic surfaces. The adhesion force of temporary adhesive measured with functionalised AFM tips was higher on hydrophobic and negatively charged surfaces for both species. Furthermore, PDMS-based surfaces were prepared varying the elastic modulus, keeping constant other parameters, settlement behaviour and strength of adhesion of juveniles and adults were tested. We conclude that cyprid settlement behaviour of both species is influenced more by surface charge than SFE under controlled conditions. The temporary adhesives (footprints) of the two species had a stronger affinity for hydrophobic surfaces. Contrary ii to previous reports, therefore, the settlement preferences and adhesive secretion of these two species are similar. Elastic modulus influences settlement, juveniles and adults removal of both species, although B. improvisus is more sensitive if compared with B. amphitrite. This finding will be important for understanding the mechanism of surface selection by cyprids and for the development of future antifouling technologies.
35
Pavey, Karl David. "Piezoelectric quartz crystal monitoring of surface interactions". Thesis, University of Brighton, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299222.
Resumen
Quartz crystal microbalances, (QCM), are high frequency oscillators, capable of nanogram mass resolution in both air and liquid environments. ~ work has produced data showing the feasibility of using the QCM for monitoring interactions in liquids for several types of systems and has allowed comparison with surface plasmon resonance (SPR) where appropriate. Bulk phase changes in viscosity and density have been used in the development of a QCM agglutination assay for the Staphylococcus epidermidis infection which has reduced diagnosis periods by a factor of twelve. Direct interactions at the crystal electrode have been employed when studying bacterial adhesion to protein treated gold surfaces. It was shown that suspensions containing as little as I x 10-2 cellsml-1 could be recognised using the QCM system. A novel boronic acid - vicinal diol interaction mechanism has been employed as a model for receptor-ligand binding. New boronic acid disulphide and short chain thiol derivatives have been synthesised and the formation of self assembled monolayers of the~e compounds monitored, both on the gold QCM electrodes and on the gold films of SPR slides, the assembly mechanism being shown to fit a two stage model shown by other workers for straight chain thiols. Monolayer orientation was confirmed using SPR, by the binding of a range of saccharides and the diol containing enzyme cofactor nicotinamide adenine dinucleotide. The enzymes lactate dehydrogenase and glucose-6-phosphate dehydrogenase have been shown to interact with bound NAD using both a novel flow injection system with QCM detection and SPR. The low molecular weight saccharide, glucose, was shown to bind reversibly to GDH on the surface of a QCM and the potential for kinetic stu4ies recognised. This was taken one step further with a preliminary investigation into sensing within real fluids, using diluted and spiked human seruin samples.
36
Oliveira, Marta Isabel Abreu. "Molecular interactions at the T cell surface". Doctoral thesis, Instituto de Ciências Biomédicas Abel Salazar, 2007. http://hdl.handle.net/10216/7220.
37
Plunkett, Mark. "Dynamic interactions of interfacial polymers". Doctoral thesis, KTH, Chemistry, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3395.
Resumen
The relationship between the amount and conformation of apolymer at the solid-liquid interface, and the resultinginteraction forces between two such surfaces has beeninvestigated. With a degree of control of the polymerconformation, by varying the temperature, solvent quality,polymer charge density etc, it has been possible to measure andinterpret the resulting changes in the surface interactions.The recurring themes of dynamics and hydrodynamics have beencontinually considered due to the large range and viscoelasticnature of the polymeric systems.
The polymeric systems investigated in this thesis are, poly(N-isopropylacrylamide), poly (12-hydroxystearate) and a seriesof AM-MAPTAC polyelectrolytes with variable chargedensities.
Adsorption and conformation of polymers have beeninvestigated by the novel QCM instrument. By comparison tosimultaneously measured energy loss information, a greaterunderstanding of the conformation of the polymer has beengained, both as a function of layer build-up during initialadsorption, and as a result of induced conformational changes.Comparing the results toin situsurface plasmon resonance and subsequent x-rayphotoelectron spectroscopy measurements, the relativeconcentration of polymer within the layer is determined. Inaddition, efforts have been made to extend the scope of thetechnique, in such ways as measuring with QCM as a function oftemperature and deriving viscoelastic properties. The later isstill to be achieved in absolute terms for polymer layers inliquid environments, yet both the principle and experimentalcapabilities have been shown.
Normal interaction forces have been measured as a functionof solvation of the polymer layer, for both adsorbed andgrafted polymer layers. For fully solvated (steric) polymerlayers, which can act as colloidal stabilisers, the dynamics ofthe repulsive force, including hydrodynamics have beeninvestigated. The same has been achieved for collapsed polymerlayers, in which the dynamic adhesion has also beeninvestigated. The effect on the adhesion of three differentdynamic mechanisms has been determined (which, like the surfaceforces, depend on the polymer conformation andviscoelasticity). These dynamic mechanisms are based onbridging forces, polymer entanglement and a viscoelasticbulkresponse from the surface layers.
Lateral or friction measurements have also been completed.The effect of load and rate have been investigated as afunction of both the polymer charge density and the underlyingsubstrate, which result in a variable conformation and bindingstrength to the substrate. This has resulted in a complexaddition of numerous mechanisms, the dominant mechanism beingdetermined by the binding strength to the surface, polymerconformation and viscoelasticity. The results have shown thatadsorbed polymer layers can be used to both increase anddecrease friction, and to change the direction of the ratedependence.
38
Liang, He. "Control of surface interactions with ultra-violet/ozone modification at polystyrene surface". Thesis, Robert Gordon University, 2014. http://hdl.handle.net/10059/948.
Resumen
Surface interactions and reactivity are of critical importance in current biomedical technologies, for example, satisfactory cell attachment and long term viability are essential for optimal in vitro tissue culture and for successful implantation and stability of cardiovascular medical implants such as stents and grafts. To achieve this, the control of fundamental forces and the resulting molecular interactions between the relevant surface and absorbing or adhering species in the physiological system is compulsory. This work utilised the surface modification technique of Ultra-Violet/ Ozone to improve the polystyrene biocompatibility by oxidising the surface with additional polar oxygen functional groups without damaging the surface bulk property. UV/Ozone treatment utilised throughout this study produced controllable oxygen functional groups and led to an increase in surface atomic oxygen level to 41% on unwashed and 35% on washed polystyrene surfaces, washing resulted in the removal of low molecular weight oxidised materials. Surface energy was increased by the addition of oxygen functional groups with the combination of alcohol (C-OR), carbonyl (C=O) and carboxyl (O-C=O); Saturation state was reached after 300s of UV/Ozone treatment where no more oxygen functionalities were incorporated to the surface. Moreover, UV/ozone treatment did not show an effect on the surface roughness studied by atomic force microscopy. The biological responses of human endothelial umbilical vein cells (HUVECs) were studied at the different level of UV/Ozone treated surfaces. HUVEC adhesion, proliferation and migration were significantly improved by the treatment compared to untreated and tissue cultures plastics (TCPs). Among the levels of UV/ozone treatment studied, 120s and 180s were found to be the most effective and HUVEC proliferation did not seem to be affected by the high level of oxygen. Similarly, the surface oxygen level did not affect the migration over UV/Ozone treated over 60s. Hypoxic condition significantly increased HUVECs migration on UV/Ozone treated, TCPs and untreated surfaces compared to normoxia, the oxygen rich surface did not favour to HUVECs that underwent regulatory process to enable the cells to increase migration. Under laminar flow conditions, HUVECs did not only grow, proliferate and migrate but also showed standard responses on UV/Ozone treated polystyrene surface. A decrease in cell size was observed at all shear stress intensities studied (1 dyn/cm2, 9 dyn/cm2 and 25 dyn/cm2) and the decrease was more obvious at higher shear stress. High shear stress intensity also induced high cell turnovers, which may be related to air bubbles induced at high flow rate. The overall findings of this study clearly illustrate that UV/Ozone surface treatment can be applied on polystyrene to improve human endothelial cells functionalities in term of adhesion, proliferation and migration in both static and laminar flow environment.
39
Balu, Balamurali. "Plasma processing of cellulose surfaces and their interactions with fluids". Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/31675.
Resumen
Thesis (Ph.D)--Chemical Engineering, Georgia Institute of Technology, 2010.Committee Chair: Breedveld, Victor; Committee Chair: Hess, Dennis; Committee Member: Aidun, Cyrus; Committee Member: Deng, Yulin; Committee Member: Singh, Preet. Part of the SMARTech Electronic Thesis and Dissertation Collection.
40
Brown, Marion Hanbury. "Physical interactions of the CD2 antigen". Thesis, Open University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.277634.
41
Ferraz, Natalia. "Effect of Surface Nanotopography on Blood-Biomaterial Interactions". Doctoral thesis, Uppsala universitet, Institutionen för fysikalisk och analytisk kemi, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-110614.
Resumen
Biologically inspired materials are being developed with the aim of improving the integration of medical implants and minimizing non-desirable host reactions. A promising strategy is the design of topographically patterned surfaces that resemble those found in the extracellular environment. Nanoporous alumina has been recognized as a potential biomaterial and as an important template for the fabrication of nanostructures. In this thesis in vitro studies were done to elucidate the role of alumina nanoporosity on the inflammatory response. Specifically, by comparing alumina membranes with two pore sizes (20 and 200 nm in diameter). Complement and platelet activation were evaluated as well as monocyte/macrophage behaviour. Whole blood was incubated with the alumina membranes and thereafter the biomaterial surfaces were evaluated in terms of protein and platelet adhesion as well as procoagulant properties. The fluid phase was analyzed for complement activation products and platelet activation markers. Besides, human mononuclear cells were cultured on the alumina membranes and cell adhesion, viability, morphology and release of pro-inflammatory cytokines were evaluated. The results indicated that nanoporous alumina with 200 nm pores promotes higher complement activation than alumina with 20 nm pores. In addition, platelet response to nanoporous alumina was found to be highly dependent on the material porosity, as reflected by differences in adhesion, PMP generation and procoagulant characteristics. A clear difference in monocyte/macrophage adhesion and activation was found between the two pore size alumina membranes. Few but highly activated cells adhered to the 200 nm membrane in contrast to many but less activated monocytes/macrophages on the 20 nm surface. The outcome of this work emphasizes that nanotopography plays an important role in the host response to biomaterials. Better understanding of molecular interactions on nano-level will undoubtedly play a significant role in biomaterial implant development and will contribute to design strategies for controlling specific biological events.
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Nussbaum, Ralph. "Surface interactions of wood with adhesives and coatings /". Stockholm, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3229.
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Perkin, Susan. "Counterion and charge correlation effects on surface interactions". Thesis, University of Oxford, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.432566.
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Preston, Alexandra McEwan. "Interactions of immunoglobulin superfamily leukocyte cell surface molecules". Thesis, University of Oxford, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318630.
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Álvarez-Asencio, Rubén. "Nanotribology, Surface Interactions and Characterization : An AFM Study". Doctoral thesis, KTH, Yt- och korrosionsvetenskap, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-145727.
Resumen
When two surfaces achieve contact, then contact phenomena such as adhesion, friction and wear can occur, which are of great interest in many disciplines, including physics, physical chemistry, material chemistry, and life and health sciences. These phenomena are largely determined by the nature and magnitude of the surface forces such as van der Waals, capillary and hydration forces. Moreover these forces are length-dependent, and therefore when the system scales down, their contribution scales up, dominating the interaction between the surfaces. A goal of my PhD work was to investigate fundamental contact phenomena in terms of the surface forces that regulate their properties. The primary tool applied in this PhD thesis work has been the atomic force microscopy (AFM), which (with all of its sub-techniques) offers the possibility to study such forces with high resolution virtually between all types of materials and intervening media. Therefore, in this work it was possible to study the long ranged interactions presented in air between different industrially relevant materials and how these interactions are shielded when the systems are immersed in an ionic liquid. Also investigated was the influence of microstructure on the tribological properties of metal alloys, where their good tribological properties were related with the vanadium and nitrogen contents for a FeCrVN tool alloy and with the chromium content for a biomedical CoCrMo alloy. Moreover, the effect of the intervening media can significantly affect the surface properties, and when the biomedical CoCrMo alloy was immersed in phosphate buffer saline solution (PBS), repulsive hydration forces decreased the friction coefficient and contact adhesion. On the other hand, with the immersion of the FeCrVN tool alloy in the NaCl solution, small particles displaying low adhesion were generated in specific regions on the surface with low chromium content. These particles are assumed to be related to a prepitting corrosion event in the tool alloy. The mechanical properties of stratum corneum (SC), which is the outermost layer of the skin, were also studied in this work. The SC presents a highly elastic, but stiff surface where the mechanical properties depend on the nanoscale. A novel probe has been designed with a single hair fibre in order to understand how the skin deforms locally in response to the interaction with such a fibre probe. This study revealed that is mostly the lateral scale of the deformation which determines the mechanical properties of the SC. Finally, important achievements in this work are the developments of two new techniques - tribological property mapping and the Hybrid method for torsional spring constant evaluation. Tribological property mapping is an AFM technique that provides friction coefficient and contact adhesion maps with information attributed to the surface microstructure. The Hybrid method is an approach that was originally required to obtain the torsional spring constants for rigid beam shaped cantilevers, which could not be previously determined from their power torsional thermal spectra (conventional method). However, the applicability is shown to be general and this simple method can be used to obtain torsional spring constants for any type of beam shape cantilever.QC 20140603
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Gillen, David R. "A study of plasma-related ion-surface interactions". Thesis, Queen's University Belfast, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.287621.
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Green, Rebecca J. "Protein/polymer interactions investigated by surface plasmon resonance". Thesis, University of Nottingham, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336926.
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Kenny, Daniel James. "Scanning tunnelling microscopy studies of cluster-surface interactions". Thesis, University of Birmingham, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.394708.
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Roberts, Shawn Conrad. "Surface/groundwater interactions in the Lincolnshire limestone aquifer". Thesis, University College London (University of London), 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313820.
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Cook, Jeanette Claire. "Experimental & theoretical studies of surface-adsorbate interactions". Thesis, University of York, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296559.