Tesi sul tema "Adhesion"
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1
Ponce, Heredia Suomi. "Adhesion of thin structures : frictional peeling and adhesive shells". Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066550/document.
Testo completoAbstract (sommario):
Dans cette thèse, nous nous intéressons à l’adhésion d’élastomères sur des substrats rigides (interactions de van der Waals). Nous revisitons ainsi, en nous appuyant sur une approche expérimentale, deux situations classiques qui permettent la mesure de l’énergie d’adhésion. Dans une première partie dédiée à l’étude du pelage, nous montrons que le frottement peut modifier le processus de détachement d’une bande d’élastomère. Ceci est tout d’abord mis en évidence lors du pelage parallèlement à l’interface, où nous montrons qu’il conduit à la progression d’une zone de frottement jusqu’au détachement de la bande pour une force proportionnelle à l’aire de contact. Nous généralisons par la suite nos résultats au pelage selon un angle quelconque. En particulier, nous montrons comment la dissipation par frottement peut augmenter de façon significative la force de pelage pour des angles faibles. Dans une deuxième partie, nous nous tournons vers la mesure d’adhésion dans une géométrie JKR, c’est à dire lors de l’indentation d’une sphère élastique adhésive avec un substrat rigide. Nous utilisons des coques élastiques dont la réponse mécanique est beaucoup plus souple bien que plus complexe. Nous montrons qu’il est néanmoins possible d’obtenir une mesure de l’adhésion par une méthode très simple et très robuste, puisqu’elle ne suppose pas de connaissance a priori de la mécanique du système. Nous espérons que cette technique permettra dans le futur d’accéder à des énergies d’adhésion très faibles ou mettant en jeu des tissus biologiques particulièrement mousIn this thesis, we are devoted to study the adhesion of elastomers to rigid substrates through van der Waals interactions. We review, from an experimental point of view, two classical methods to measure the adhesion energy. A first part is dedicated to the study of the peeling system, we show that friction can modify the detachment process of an elastomer strip. This is firstly observed in the lap-test configuration, where a sliding front propagates on the interface up until the end of the strip, for a pulling force proportional to the initial contact area. We generalize this results for the finite peeling angle case. In particular, we show how the friction dissipation significantly increases for small peeling angles. In the second part, we study the adhesion measure in the JKR geometry, i.e. for the indentation of an adhesive elastic sphere into a rigid plate. We use elastic thin shells, which elastic response is much softer, as well it is much more complex. However, it is possible to measure the adhesion energy through a very simple and robust method with no need of much details of the mechanical response of the system. We hope this technique will allow to measure the effect of very weak and sensitive adhesive systems such us biological tissues which are particularly soft
2
Muniz, Maisonet Maritza. "Topographical Enhancement of Cell Adhesion on Poorly Adhesive Materials". Scholar Commons, 2015. https://scholarcommons.usf.edu/etd/5748.
Testo completoAbstract (sommario):
The overall thrust of this dissertation is to gain a fundamental understanding of the synergistic effects between surface topography and chemical functionality of poorly adhesive materials on enhancing the adhesion of mouse embryonic fibroblasts. Cellular response to surface topography and chemical functionality have been extensively studied on their own providing valuable information that helps in the design of new and improved biomaterials for tissue engineering applications. However, there is a lack of understanding of the synergistic effect of microscale and nanoscale topography with chemical functionality and the relative impact and contribution of each in modulating cellular behavior. By understanding the relationship between these cues, in particular using materials that are poorly adhesive, this study will provide new clues as to how cells adapt to their environment and also suggest new dimensions of biomaterial design for fine-tuning cellular control.
A microstructure that combined non adhesive materials with defined surface topography and surface chemistry is presented, to assess and correlate the enhancement of mouse embryonic fibroblasts cell adhesion and spreading. Poly (N-isopropylacrylamide) or PNIPAAm electrospun fibers were overlaid on PNIPAAm thin films (100 nm) at various time points to investigate the role of topography on such coatings by keeping the chemical functionality the same. After doing this, several topographical patterns were developed, spanning from sparse to dense fiber mats, and cell adhesion strongly depended on the relative available areas for attachment on either the fibers or the supporting surface. To gain a better understanding of this finding, two surface chemistries, non-adhesive (self-assembled monolayer of polyethylene glycol (PEGSAM) alkanethiol on gold) or an adhesive coating (3-aminopropyltriethoxysilane (APTES) on glass) with well characterized adhesive properties were included in this study to assess the effect of topographical cues provided by the PNIPAAm electrospun fibers on cellular responses. With the deposition of the PNIPAAm fibers onto a PEGSAM surface, cell adhesion increased to almost 100%, and unlike the PNIPAAm surface, cell spreading was significantly enhanced. With the deposition of PNIPAAm fibers onto APTES, both cell adhesion and spreading were unaffected up to 60% fiber coverage. For both surfaces, PNIPAAm fiber densities above 60% coverage lead to adhesion and spreading independent of the underlying surface. These findings indicate the presence of a sparse topographical feature can stimulate cell adhesion on a typically non-adhesive material, and that a chemical dissimilarity between the topographic features and the background enhances this effect through greater cell-surface interaction.
In addition to the aforementioned studies, cell response was also assessed on PNIPAAm thin films coatings with thicknesses ranging from 100 nm to 7 nm. Cell adhesion and spreading was enhanced as the thickness of the thin film decreased. This change was more noticeable below 30 nm, wherein 7 nm shows the highest cell adhesion and spreading enhancement. The results reported are preliminary results and further experiments will be conducted, to support the data. It is believed that cellular response was enhanced due to a change in surface topography at the nanoscale level.
3
Kessler, Amanda. "Intercoat adhesion : How can intercoat adhesion be studied and what influences intercoat adhesion". Thesis, KTH, Skolan för kemi, bioteknologi och hälsa (CBH), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-230693.
Testo completoAbstract (sommario):
Coatings cover most objects in our daily lives. They can have functional properties such as protecting the coated material or esthetic properties to decorate and provide pleasant appearance. Coatings have historically dried by evaporation of solvents, but now, UV curing coatings are on the uprising. Acrylate functional groups on polymers, oligomers and monomers react through radical chain polymerization initiated by photoinitiators. Photoinitiators are molecules which forms radicals when irradiated with UV light.Coatings are often applied on multiple layers, each layer providing one function for the overall system. To function properly and have desired life time the layers must adhere to each other. The problem of intercoat adhesion has yet to find good techniques for analysis and explanation of what influences it. Many theories have been suggested and most likely many play a part in the overall adhesion.The master thesis project aim to investigate which properties that influences intercoat adhesion and how it can be studied. To relate properties of coatings to the intercoat adhesion one UV curing primer is set to use for all coating systems, and various topcoats have been produced with slight changes in formulation. The study can be divided into two parts; a pre-study and a main study. The pre-study follows up on a previous master thesis conducted at Sherwin-Williams AB. The pre-study has waterbased and waterbased UV-curable topcoats. The main study has UV curable topcoats. Properties which are studied in the main study are chemical backbone of the binder, functionality of monomers, influence of addition of wetting agents, defoamers, fillers and pigment, viscosity, density, pH, curing degree at depth, surface energy, surface tension, surface polarity and monomer to binder ratio.The pull-off method is the best method of analysis of intercoat adhesion today. A dolly is glued to a surface and then lifted, the force of lifting the dolly is measured. The method has one significant drawback; the break must be completely in the interphase of where the adhesion wishes to be analyzed. Throughout this study most interphase failures were between substrate and primer, resulting in no value for intercoat adhesion.No correlation was found between intercoat adhesion and chemical backbone of the binder, functionality of monomers, addition of wetting agents, defoamers, viscosity, pH, surface energy, surface tension or surface polarity. Lower intercoat adhesion was observed for coatings containing talc, calcium carbonate and titanium dioxide. Coating containing titanium dioxide showed insufficient curing above a coating thickness of 40 μm. The insufficient curing could be observed as wrinkles on the surface and liquid coating remaining in the coating interphase. Curing degree in depth of the topcoat is believed to be the main reason to decreased intercoat adhesion for the coating containing titanium dioxide. The insufficient curing could not be confirmed with infrared spectrometry. The reason why talc and calcium carbonate showed decreased intercoat adhesion is not known. Indications suggest that a lower monomer to binder ratio decrease intercoat adhesion, theories to explain this are the high viscosity and the low number of functional groups per volume. A higher number of functional groups per volume could increase the number of crosslinks formed between topcoat and primer.Färger finns överallt omkring oss. De kan ha funktionella egenskaper så som att skydda det målade materialet eller ge ett önskvärd utseende. Ett bord ska både tåla att få spillt kaffe på sig och se behagligt ut. Ofta appliceras färger i flera lager för att uppnå önskade egenskaper och utseende. Dessa färglager bör sitta bra i varandra för att inte avflagning ska uppstå. Hur bra färgskikten sitter i varandra kallas mellanskiktsvidhäftning. Mellanskiktsvidhäftning har varit en utmaning genom hela färgindustrins historia och ännu har inga entydiga förklaringar på vad som påverkar eller hur man ska mäta det uppkommit.Kommersiella färger har historiskt varit lösningsmedelsbaserade och torkat. Torkning innebär att flyktiga komponenter i färgen avgår genom att evaporera. I och med moderna försök att minska negativa effekter på miljön har vattenbaserade och helt lösningsmedelsfria färger utvecklats. De lösningsmedelfria färgerna torkar inte utan färgfilmen formas genom en kemisk reaktion initierad med hjälp av ultraviolett (UV) ljus. Ett tidigare examensarbete utfört på Sherwin-Williams AB undersökte mellanskiktsvidhäftningen för en UV härdande grund med vattenbaserade topplacker. Detta projekt är menat som en fortsättning på tidigare projekt men fokuserar huvudsakligen på UV härdande topplacker på en låst UV härdande grund. Syftet med studien är att undersöka hur olika egenskaper hos topplacker påverkar mellanskiktsvidhäftningen samt undersöka hur man kan studera mellanskiktsvidhäftning.Den främsta metoden för att undersöka mellanskiktsvidhäftning konstaterades vara dragprovsmätning, då övriga mätmetoder inte ger entydiga resultat. I dragprovningsmetoden limmas en metallknopp på en yta för att sedan dras av vinkelrätt från ytan och kraften som krävs mäts. Nackdelen med metoden är att för att kunna mäta specifikt mellanskiktvidhäftningen måste brottet ske i gränsskiktet mellan färgerna. Brottet uppstod framförallt mellan substrat och grundfärg under studien.Resultaten från studien kunde inte påvisa ett samband mellan den kemiska strukturen av bindemedlet, antalet funktionella grupper på monomer, tillsatser av vätmedel, skumdämpare, viskositet, densitet, pH, ytenergi, ytspänning, ytpolaritet samt krympning av filmen vid härdning. Resultaten indikerar att tillsats av talk, krita eller titandioxid minskar mellanskiktsvidhäftningen. Anledningen till att talk samt krita minskar mellanskiktsvidhäftningen kan ej förklaras. Titandioxiden påverkade uthärdningen av filmen vilket tros vara anledningen till den minskade mellanskiktsvidhäftningen. Det går att se en indikation att minskat förhållande av vikten monomerer mot vikten bindemedel i färgformuleringen minskade mellanskiktsvidhäftnigen. Detta tros bero på en minskad mängd funktionella akrylatgrupper per volym samt ökad viskositet. Förstudien som använde vattenbaserade och vattenbaserade UV härdande topplacker indikerade en försämrad mellanskiktsvidhäftning för rena vattenbaserade system på UV härdande primer.
4
Elineni, Kranthi Kumar. "Regulation of Cell Adhesion Strength by Spatial Organization of Focal Adhesions". Scholar Commons, 2011. http://scholarcommons.usf.edu/etd/3088.
Testo completoAbstract (sommario):
Cell adhesion to extracellular matrix (ECM) is critical to various cellular processes like cell spreading, migration, growth and apoptosis. At the tissue level, cell adhesion is important in the pathological and physiological processes that regulate the tissue morphogenesis. Cell adhesion to the ECM is primarily mediated by the integrin family of receptors. The receptors that are recruited to the surface are reinforced by structural and signaling proteins at the adhesive sites forming focal adhesions that connect the cytoskeleton to further stabilize the adhesions. The functional roles of these focal adhesions extend beyond stabilizing adhesions and transduce mechanical signals at the cell-ECM interface in various signaling events. The objective of this research is to analyze the role of the spatial distribution of the focal adhesions in stabilizing the cell adhesion to the ECM in relation to cell's internal force balance. The central hypothesis was that peripheral focal adhesions stabilize cell adhesion to ECM by providing for maximum mechanical advantage for resisting detachment as explained by the membrane peeling mechanism. Micropatterning techniques combined with robust hydrodynamic shear assay were employed to test our hypothesis. However, technical difficulties in microcontact printing stamps with small and sparse features made it challenging to analyze the role of peripheral focal adhesions in stabilizing cell adhesion. To overcome this limitation, the roof collapse phenomenon in stamps with small and sparse features (low fill factor stamps) that was detrimental to the reproduction of the adhesive geometries required to test the hypothesis was analyzed. This analysis lead to the valuable insight that the non-uniform pressure distribution during initial contact caused by parallelism error during manual microcontact printing prevented accurate replication of features on the substrate. To this end, the template of the stamp was modified so that it included an annular column around the pattern zone that acted as a collapse barrier and prevented roof collapse propagation into the pattern zone. Employing this modified stamp, the required geometries for the cell adhesion analysis were successfully reproduced on the substrates with high throughput. Adhesive areas were engineered with circular and annular patterns to discern the contribution of peripheral focal adhesions towards cell adhesion strength. The patterns were engineered such that two distinct geometries with either constant adhesive area or constant spreading area were obtained. The significance of annular patterns is that for the same total adhesive area as the circular pattern, the annular pattern provided for greater cell spreading thereby increasing the distance of the focal adhesions from the cell's center. The adhesion strength analysis was accomplished by utilizing hydrodynamic shear flow in a spinning disk device that was previously developed. The results indicate that for a constant total adhesive area, the annular patterns provide for greater adhesion strength by enhancing cell spreading area and providing for greater moment arm in resisting detachment due to shear. The next examination was the effect of the cell's internal force balance in stabilizing the cell adhesion. The working hypothesis was that microtubules provide the necessary forces to resist the tensile forces expressed by the cell contractile machinery, thereby stabilizing cell adhesion. Since microtubule disruption is known to enhance cell contractility, its effect on the cell adhesion strength was examined. Moreover, the force balance in cells was altered by engineering adhesive areas so that the cells were either spherical or completely spread and then disrupted microtubules to understand the significance of the force balance in modulating the cell adhesion strength. The results indicated that disruption of microtubules in cells on adhesive islands resulted in a 10 fold decrease in adhesion strength compared to untreated controls whereas no significant change was observed in completely spread cells between treated and untreated controls. This is in surprising contrast to the previous contractility inhibition studies which indicate a less pronounced regulation of adhesion strength for both micropatterned and spread cells. Taken together, these findings suggest that the internal force balance regulated by cell shape strongly modulates the adhesion strength though the microtubule network. In summary, this project elucidates the role of peripheral focal adhesions in regulating the cell adhesion strength. Furthermore, this study also establishes the importance of the internal force balance towards stabilizing the cell adhesion to the ECM through the microtubule network.
5
Zhao, Lee Cheng. "Cell adhesion characterization of adhesive forces and effect of topography /". [Gainesville, Fla.] : University of Florida, 2000. http://etd.fcla.edu/etd/uf/2000/ana7043/LCZhao%5FThesis.pdf.
Testo completoAbstract (sommario):
Thesis (M.S.)--University of Florida, 2000.Title from first page of PDF file. Document formatted into pages; contains ix, 79 p.; also contains graphics. Vita. Includes bibliographical references (p. 69-77).
6
Fredriksson, Fanny. "Outcome and prevention strategies in peritoneal adhesion formation". Doctoral thesis, Uppsala universitet, Barnkirurgi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-282119.
Testo completoAbstract (sommario):
Peritoneal adhesions occur in up to 93% of adults after peritoneal trauma during surgery. Most adhesions are asymptomatic but can cause female infertility, small bowel obstruction (SBO) and chronic abdominal pain. Adhesion prophylaxis is needed to reduce the significant morbidity and increased health care costs resulting from peritoneal adhesions. This thesis aims to establish a relevant and reproducible experimental adhesion model to simultaneously study the healing processs and adhesion formation and later to examine whether carbazate-activated polyvinyl alcohol (PVAC), an aldehyde-carbonyl scavenger, can reduce adhesion formation or not; and, in a long-term follow-up, to investigate the incidence of and identify risk factors for adhesive SBO requiring surgical treatment after laparotomy during infancy and to survey the prevalence of self-reported chronic abdominal pain and female infertility. Male Sprague-Dawley rats were subjected to laparotomy, cecal abrasion, and construction of a small bowel anastomosis and examined at various time points after surgery. Early elevation of IL-6, IL-1β and TNF-α concentrations in peritoneal fluid but not in plasma correlate to adhesion formation in this rodent adhesion model, indicating that anti-adhesion treatment should be early, local and not systemic. The animals were treated with either peritoneal instillation of PVAC, or the anastomosis was sutured with PVAC-impregnated resorbable polyglactin sutures. At day 7, bursting pressure of the anastomosis was measured and adhesions were blindly evaluated using Kennedy- and Nair scoring systems. PVAC-impregnated sutures reduced adhesion formation without reducing bursting pressure. Infants who underwent laparotomy between 1976 and 2011 were identified (n=1185) and 898 patients were included with a median follow-up time of 14.7 (range 0.0-36.0) years. The median age at first laparotomy was 6 (range 1.0-365.0) days. There were 113 patients (12.6%) with adhesive SBO, with the highest incidence found in patients with Hirschsprung’s disease (19 of 65, 29%), malrotation (13 of 45, 29%), intestinal atresia (11 of 40, 28%) and necrotizing enterocolitis (16 of 64, 25%). Lengthy duration of surgery (hazard ratio (HR) 1.25, 95% CI, 1.07 to 1.45), stoma formation (HR 1.72, 1.15 to 2.56) and postoperative complications (HR 1.81, 1.12 to 2.92) were independent risk factors. Chronic abdominal pain was reported in 180 (24.0%) of 750 patients, and 17 (13.8%) of 123 women reported infertility. The morbidity after laparotomy in neonates and infants is high. Awareness of the risk factors may promote changes in surgical practice.
7
Jordan, Allison Clare. "Modelling platelet adhesion". Thesis, University of Leeds, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.410947.
Testo completo
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Coyer, Sean R. "Modulation of cell adhesion strengthening by nanoscale geometries at the adhesive interface". Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/34763.
Testo completoAbstract (sommario):
Cell adhesion to extracellular matrices (ECM) is critical to many cellular processes including differentiation, proliferation, migration, and apoptosis. Alterations in adhesive mechanisms are central to the behavior of cells in pathological conditions including cancer, atherosclerosis, and defects in wound healing. Although significant progress has been made in identifying molecules involved in adhesion, the mechanisms that dictate the generation of strong adhesive forces remain poorly understood. Specifically, the role of nanoscale geometry of the adhesive interface in integrin recruitment and adhesion forces remains elusive due to limitations in the techniques available for engineering cell adhesion environments. The objective of this project was to analyze the role of nanoscale geometry in cell adhesion strengthening to ECM. Our central hypothesis was that adhesive interactions are regulated by integrin clusters whose recruitment is determined by the nanoscale geometry of the adhesive interface and whose heterogeneity in size, spacing, and orientation modulates adhesion strength.
The objective of this project was accomplished by 1) developing an experimental technique capable of producing nanoscale patterns of proteins on surfaces for cell adhesion arrays, 2) assessing the regulation of integrin recruitment by geometry of the adhesive interface, and 3) determining the functional implications of adhesive interface geometry by systematically analyzing the adhesion strengthening response to nanoscale patterns of proteins. A printing technique was developed that patterns proteins into features as small as 90nm with high contrast and high reproducibility. Cell adhesion arrays were produced by directly immobilizing proteins into patterns on mixed-SAMs surfaces with a protein-resistant background. Colocalization analysis of integrin recruitment to FN patterns demonstrated a concentrating effect of bound integrins at pattern sizes with areas equivalent to small nascent focal adhesions. At adhesion areas below 333 × 333 nm2, the frequency of integrin recruitment events decreased significantly indicating a threshold size for integrin clustering. Functionally, pattern sizes below the threshold were unable to participate in generation of adhesion strength. In contrast, patterns between the threshold and micron sizes showed a relationship between adhesion strength and area of individual adhesion points, independent of the total available adhesion area. These studies introduce a robust platform for producing nanoscale patterns of proteins in biologically relevant geometries. Results obtained using this approach yielded new insights on the role of nanoscale organization of the adhesive interface in modulating adhesion strength and integrin recruitment.
9
Marcus, Hilda. "Adherence of Pseudomonas aeruginosa to perfused tracheal epithelium : adhesin [i.e. adhesion] - receptor interactions /". The Ohio State University, 1985. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487259580261697.
Testo completo
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Sambasivan, Nadarajah. "The adhesion of an optical adhesive to glass substrates for optoelectronics applications". Thesis, University of Surrey, 2001. http://epubs.surrey.ac.uk/843340/.
Testo completoAbstract (sommario):
Surface characterisation and failure mechanisms of adhesively bonded glass butt joints were studied. Materials of relevance to the adhesive bonding of fibre optic components were employed: a fine annealed Grade A glass (Schott(TM) BK - 7), and a fast curing epoxy based optical adhesive. The joint behaviour and their durability under adverse environmental conditions were investigated, and the subsequent, failed joint fracture surfaces were examined using XPS, ToF-SIMS and SEM. Surface analysis techniques have been employed to characterise components of the adhesive systems and to interrogate the surface of failed joints with a view to establishing the locus of failure. Joints were immersed in pure water for period of 0 - 270 days at 35°C. Substantial reduction in the bond strength within a few days of water immersion was observed. Also for the joints left in for a prolonged exposure periods (> 100 days) the strength values reached a minimum value. The surface analysis of the joints has indicated a cochoidal brittle fracture through the adhesive in dry conditions, and an interfacial failure for wet joint fractures. Calculations of the polymer thickness on the interfacial surfaces indicated a decrease in overlayer thickness. This reduction reached a constant value for joints left in water for more than 100 days. During this investigation surfaces segregation of minor components of the adhesive such as amine and diluent was also identified by ToF-SIMS and XPS. In order to study this phenomenon further, reformulation of the adhesive has been carried out. Six adhesives were formulated, of which three resins were based on the change in diluent content of the system, three were based on the change in amine concentrations. This work has clearly identified amine segregation only at the interfacially failed joints. It is expected that when the joints cures very fast, even if the formulation contains very high proportion of amine, the segregation is minimal. Also, some evidence of diluent migration at the interfaces was observed during the reformulation studies.
11
McKendrick, Joseph James. "Epithelial ovarian cancer cell adhesion to extracellular matrix proteins and the effect on adhesion of peptide inhibitors of adhesion receptors". Thesis, University of Southampton, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316401.
Testo completo
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Hefer, Arno Wilhelm. "Adhesion in bitumen-aggregate systems and quantification of the effect of water on the adhesive bond". Texas A&M University, 2004. http://hdl.handle.net/1969.1/1457.
Testo completoAbstract (sommario):
This research is intended to contribute toward the understanding, development, and
implementation of a more fundamental design process for bituminous pavement
materials, utilizing thermodynamic properties of the materials involved. The theory
developed by van Oss, Chaudhury and Good forms the basis of this research.
Optimization of techniques to characterize surface energy, as well as consideration and
evaluation of additional factors that influence adhesion in the presence of water, are
pursued. A synthesis of theories and mechanisms of bitumen-aggregate adhesion is
presented, and existing and potential techniques for surface energy characterization are
reviewed to establish firm background knowledge on this subject.
The Wilhelmy plate technique was scrutinized and improved methodologies and
analysis procedures are proposed. Inverse gas chromatography (IGC) is introduced as an
alternative technique. A reasonable comparison of total surface energy values form
these techniques with mechanical surface tension values were found. Results suggest
that bitumen surface energies do not vary substantially. Inability of these techniques to
detect the effect of a liquid additive is rationalized by the potential surface energy
concept. Suggestions for a more realistic characterization of bitumen polar surface
energy components are presented.
A static gravimetric sorption technique was employed to characterize aggregate
surface energies. Dynamic vapor sorption was identified as a candidate alternative
technique for aggregate surface energy characterization.
A study on the effect of pH on surface energy components of water revealed that this
effect is practically negligible. Calculation of the free energy of electrostatic interaction
(DGEL) indicated that this term contributes less than 1% to the total free energy of
adhesion. Despite this finding, it is shown that DGEL alone is able to distinguish
moisture sensitive mixtures. The significance of electrical phenomena at the interface is
elucidated through another mechanism following the work of M.E. Labib. The
relationship between pH and electron donor-acceptor properties of aggregate surfaces is
presented. The Labib approach potentially offers the solution to quantify the effect of
pH on adhesion. In addition, it should be possible to resolve issues with the acid-base
scale proposed by the founders of the current theory, by replacing it with a more
absolute donor-acceptor scale.
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Mohd, Jakarni Fauzan. "Adhesion of asphalt mixtures". Thesis, University of Nottingham, 2012. http://eprints.nottingham.ac.uk/12646/.
Testo completoAbstract (sommario):
Adhesion is defined as the molecular force of attraction in the area of contact between unlike bodies of adhesive materials and substrates that acts to hold the bodies together. In the context of asphalt mixtures, adhesion is used to refer to the amount of energy required to break the adhesive bond between bitumen (bitumen-filler mastic) and aggregates. Thus, adhesive failure can be considered as displacement of bitumen (bitumen-filler) mastic from aggregates surface, which might indicates low magnitude of adhesive bond strength. Adhesion is considered as one of the main fundamental properties of asphalt mixtures, which can be correlated with quality, performance and serviceability. However, despite its significance, research on adhesion of asphalt mixtures is limited and yet there is no established testing technique and procedure that can be used to quantify the adhesive bond strength between bitumen (bitumen-filler mastic) and aggregates. Only in the past few years, some efforts have been conducted in developing testing techniques and procedures for measuring the adhesive bond strength of bitumen and aggregates. However, the developed testing techniques and procedures have not enjoyed universal success and acceptance, and not yet established. Hence, emphasis of this study is focused on the development of laboratory adhesion test method that can be used to directly measure the adhesive bond strength between bitumen (bitumen-filler mastic) and aggregates. Also, adhesive bond strength and failure characteristics of various combinations of asphalt mixture materials over wide ranges of testing conditions were evaluated in order to validate the reliability and efficiency of the developed laboratory adhesion test method. This study was divided into three parts. In Part 1, a detailed review of literature on various testing techniques and procedures used to measure the adhesive bond strength in numerous areas of scientific literature and international standards was performed, in order to assess and thus to propose the most suitable and realistic approach for development of laboratory adhesion test method for asphalt mixtures. In Part 2, the proposed adhesion test method was subjected to evaluation, mainly based on trial and error experimental approach, in order to adapt and thus to develop the criteria and procedures for test setup and apparatus, specimen preparation, testing and data analysis. The established criteria and procedures were then used for detailed evaluation in Part 3, in order to quantify the test results of various combinations of asphalt mixture materials (i.e. bitumen (bitumen-filler mastic) and aggregates) over wide ranges of thicknesses of adhesive layer of bitumen, aspect ratio of specimens, testing conditions (i.e. deformation rates and test temperatures) and conditioning procedures (dry and wet conditionings). Results of the study were subjected to comparative analysis in order to determine the effect of various variables and parameters on the test results, to propose suitable testing conditions and to validate the reliability and efficiency of the laboratory adhesion test method. Upon completion of the study, a draft protocol was developed as guiding principles in conducting the laboratory adhesion test method.
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Darmani, Homa. "Erythrocyte adhesion by macromolecules". Thesis, Cardiff University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.278681.
Testo completo
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Johnson-Tidey, Ruth R. "Monocyte adhesion in atherosclerosis". Thesis, King's College London (University of London), 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387903.
Testo completo
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Dix, Christina Lyn. "Adhesion-dependent cell division". Thesis, University College London (University of London), 2018. http://discovery.ucl.ac.uk/10044469/.
Testo completoAbstract (sommario):
Animal cells undergo a dramatic series of cell shape changes as they pass through mitosis and divide which depend both on remodelling of the contrac- tile actomyosin cortex and on the release of cell-substrate adhesions. Here, I use the adherent, non-transformed, human RPE1 cell line as a model system in which to explore the dynamics of these shape changes, and the function of mitotic adhesion remodelling. Although these cells are highly motile, and therefore polarised in interphase, many pause migration and elongate to be- come bipolar prior to mitosis. Interestingly, and in contrast to most reported cell types, these cells do not round fully, and many leave long adhesive tails con- nected to the underlying substrate. These are typically bipolar, persist through- out mitosis, and guide cell respreading following mitotic exit. Further analysis shows that while many proteins are lost from focal adhesion complexes during mitotic rounding, integrin-rich contacts remain in place along these tails as well as defining the tips of retraction fibres. These adhesions are functionally impor- tant in RPE1 cells, since these cells fail to divide when removed from the sub- strate prior to entry into mitosis. The restoration of cell-substrate adhesions at anaphase are sufficient to rescue division in control cells. However, adhesions must persist into mitotic exit for division in cells compromised in their ability to construct an actomyosin ring. Division in these cells depends on respreading, since Ect2 RNAi cells fail to divide on small adhesive islands, but successfully divide on larger patterns with the cytoplasmic bridge connecting daughter cells narrowing as they migrate away from one another. Together these results re- veal the importance of coupling adhesion remodeling to mitotic progression.
17
Yang, Jiankai. "Measuring adhesion between particles". Thesis, University of Sheffield, 2018. http://etheses.whiterose.ac.uk/21276/.
Testo completo
18
Benson, Bryan Lauck. "Mechanobiology of Leukocyte Adhesion". Case Western Reserve University School of Graduate Studies / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=case1537210425881461.
Testo completo
19
Fitton, J. H. "Cells, surfaces and adhesion". Thesis, Aston University, 1993. http://publications.aston.ac.uk/9752/.
Testo completoAbstract (sommario):
This thesis concerns cell adhesion to polymer surfaces with an experimental emphasis on hydrogels. The thesis begins with a review of the literature and a synthesis of recent evidence to describe the process of cell adhesion in a given situation. The importance of understanding integrin-adhesion protein interactions and adhesion protein-surface interactions is emphasised. The experimental chapters describe three areas of investigation. Firstly, in vitro cell culture techniques are used to explore a variety of surfaces including polyethylene glycol methacrylate (PEGMA) substituted hydrogels, sequence distribution modified hydrogels and worn contact lenses. Cell adhesion to PEGMA substituted gels is found to decrease with increases in polyethylene oxide chain length and correlations are made between sequence distribution and adhesion. Worn contact lenses are investigated for their cell adhesion properties in the presence of antibodies to specific adhesion proteins, demonstrating the presence of vitronectin and fibronectin on the lenses. The second experimental chapter addresses divalent cation regulation of integrin mediated cell adhesion. Several cell types and various cations are used. Zinc, previously not regarded as an important cation in the process, is found to inhibit 3T3 cell adhesion to vitronectin that is promoted by other divalent cations. The final experimental chapter concerns cell adhesion and growth on macroporous hydrogels. A variety of freeze-thaw formed porous gels are investiated and found generally to promote cell growth rate.Interpenetrating networkbased gels (IPN) are made porous by elution of dextrin particles of varying size and loading density. These materials provide the basis for synthetic cartilage. Cartilage cells (chondrocytes) plated onto the surface of the porous IPN materials maintain a rounded shape and hence phenotypic function when a critical pore size and density is achieved. In this way, a prospective implant, made porous at the perpendicular edges contacting natural cartilage can be both mechanically stabilised and encourage the maintenance of normal matrix production at the tissue interface.
20
Kugele, Michael. "Adhesion in lepadomorph barnacles". Thesis, Bangor University, 1996. https://research.bangor.ac.uk/portal/en/theses/adhesion-in-lepadomorph-barnacles(b51bacf5-2b6a-48cd-9927-bf9c4c455468).html.
Testo completoAbstract (sommario):
The larvae of Pollicipes pollicipes were succesfully reared in the laboratory and their morphological characteristics described and compared to the previously described P. polymerus. Attempts to induce apparently healthy cyprids to settle in quantity, using methodology commonly employed for balanomorph barnacles, were unsuccessful indicating the lack of some major settlement cue(s). The scalpellids P. pollicipes and Capitulum mitella were shown able to voluntarily relocate, with measured speeds of up to 50 gm d'', but the lepadid Lepas anatifera cannot do so. The scalpellids used different mechanisms for relocation although both involved growth and sloughing of basal integument. A stimulus for directed travel was not found but gravity and unidirectional flow were rejected. The cement of lepadomorphs was shown to dissolve very slowly in sterile seawater. Cement in flowing seawater tanks, or in the presence of bacterial isolates collected from the cement, or in the presence of protease concentrated from bacterial cultures, did not dissolve at faster rates, to that of sterile cement, than could be explained by the sample sizes. The proteinaceous cement of P. pollicipes was delivered as a liquid in nl quantities over a period of 5-20 minutes before curing which took around 2 hours. Cement masses cured in seawater were found to be zoned due to a variable volume of space within, whilst cement delivered and cured in air or nitrogen was homogeneous. It was determined that the more porous inner zone of cement masses was inhibited from curing fully as a result of an inability to displace water. The partially cured zone could be induced to cure fully, by heating to dryness from a minimal volume of water. The presence of water was determined to be essential for curing. Differential degrees of curing of cement masses allowed for various physical and histochemical treatments which support both the rejection of disulphide bonding and phenol tanning and the growing evidence of hydrophobic complexing as central to the solidification mechanism of barnacle cement.
21
Xu, Dingying. "Durability and Adhesion of a Model Epoxy Adhesive Bonded to Modified Silicon Substrates". Diss., Virginia Tech, 2004. http://hdl.handle.net/10919/28166.
Testo completoAbstract (sommario):
The adhesion and durability of model epoxy/silane/SiO2/Si bonded systems were investigated under various conditions, including the type of surface preparation, pH of the environmental media, temperature, cyclic thermal stress, and external applied stress. The fundamental debond mechanism was studied for bonded systems exposed to selected environments. The bond failure mode was characterized by examining the failed bond surfaces using X-ray photoelectron spectroscopy.
The effectiveness of combining the oxygen plasma treatment and silane coupling agent (SCA) derivatization in adhesion promotion for an epoxy bonded to a silicon surface was evaluated in this research. SCAs with different amine functionalities were studied. The oxygen plasma treatment time was varied systematically to achieve a different extent of oxidation on the Si wafer. The surface chemistry/composition of various silane derivatized Si surfaces was investigated. The studies revealed that SCA interaction with the Si surface was enhanced by the oxygen plasma pre-treatment of the Si substrates. XPS surface analysis results showed that the SCA/SiO2 ratio did not correlate strongly with the increase in oxygen plasma pretreatment time. However, for Si surfaces treated for longer oxygen plasma pretreatment times, more silanol groups may be available to interact with the hydrolyzed silanol groups on silane, resulting in a stronger SCA-Si attachment.
Three different tests were employed to determine adhesion and durability of the model epoxy/SCA/SiO2/Si bonded specimens. The immersion test qualitatively evaluates the bond durability for various systems exposed to different chemical and thermal conditions. Second, a novel probe test was used to quantitatively determine adhesion under critical debonding conditions for bonded specimens with different SCA preparations. A general trend of bond durability varied in the manner SCA-2 > SCA-3 > SCA-1 > no silane. Bond durability also increased for samples: model epoxy/SCA modified/O2 plasma treated/Si as the oxygen plasma pre-treatment time increased. Third, bond durability was studied using the wedge DCB (double cantilever beam) test under subcritical debonding conditions with environment-assisted crack growth as a function of applied strain energy release rate. Higher crack velocity and the absence of a Gthreshold value were noted in tests at 70 oC. The Gthreshold value increased as the strength of the interface increased and as the chemical aggressiveness of the environment decreased. For tests involving 25 oC -70 oC thermal cycling, only limited crack growth was found.Ph. D.
22
Stewart, Alasdair Gwilym. "Studies of focal adhesion kinase in epithelial cells : involvement in cell-cell adhesion". Thesis, University College London (University of London), 2005. http://discovery.ucl.ac.uk/1446839/.
Testo completoAbstract (sommario):
Epithelial cell-cell adhesion is mediated by tight junctions, adherens junctions and desmosomes. Epithelial cell-matrix adhesion is mediated by hemidesmosomes and focal contacts. These complexes exhibit great plasticity, and each contains molecular components which are able to participate in one or more of the other adhesive complexes. Focal adhesion kinase (FAK/pl25FAK) is a non-receptor tyrosine kinase which transduces signals from integrins at sites of focal contact to promote adhesion, spreading and migration. FAK possesses a central kinase domain which is flanked by large, non-catalytic, amino- and carboxy-terminal domains. Whereas the functions of the carboxy-terminal and kinase domains of FAK are well understood, the role of the amino-terminal domain remains unclear. FAK expression was examined in the human epithelial cell line, HEK 293. Amino-terminal FAK immunoreactivity was noted at sites of cell-cell contacts and in the nucleus, in contrast to carboxy-terminal immunoreactivity, which was largely cytoplasmic and perinuclear. Western blot analysis of endogenous FAK revealed expression of a presumptive proteolytic cleavage fragment corresponding to the amino- terminal domain. A series of FAK constructs was generated to test the hypothesis that the observed amino-terminal FAK localisation was due to this proteolytic fragment. Epitope- tagged Amino-Terminal FAK (ATF) constructs localised primarily at areas of cell-cell contact and in the nucleus in HEK 293 cells. This localisation was independent of Tyrosine 397, the major FAK autophosphorylation site. This sub-cellular distribution was confirmed in another epithelial cell line, MDCK, in which transiently transfected ATF constructs also localised primarily to the nucleus and at cell-cell contacts. HEK 293 cells were characterised with respect to expression of adhesive proteins, and ATF was found to co- localise with the tight junction protein occludin, with cortical actin and with junctional ?1 integrin. Immunoprecipitation data suggests that none of these proteins forms a precipitable complex with ATF. These findings indicate that the amino-terminal domain of FAK is capable of localising at epithelial cell-cell contacts and suggest a novel role for FAK in mediating cross-talk between focal contacts and cell-cell contacts through endogenously expressed amino-terminal FAK fragments.
23
Liu, Haijing. "Wet adhesion properties of oilseed proteins stimulated by chemical and physical interactions and bonding". Diss., Kansas State University, 2017. http://hdl.handle.net/2097/35774.
Testo completoAbstract (sommario):
Doctor of PhilosophyDepartment of Grain Science and Industry
X. Susan Sun
The ecological and public health liabilities related with consuming petroleum resources have inspired the development of sustainable and environmental friendly materials. Plant protein, as a byproduct of oil extraction, has been identified as an economical biomaterial source and has previously demonstrated excellent potential for commercial use. Due to the intrinsic structure, protein-based materials are vulnerable to water and present relatively low wet mechanical properties. The purpose of this study focuses on increasing protein surface hydrophobicity through chemical modifications in order to improve wet mechanical strength. However, most of the water sensitive groups (WSG), such as amine, carboxyl, and hydroxyl groups, are also attributed to adhesion. Therefore, the goal of this research is to reduce water sensitive groups to an optimum level that the modified soy protein presents good wet adhesion and wet mechanical strength. In this research, we proposed two major approaches to reduce WSG: 1). By grafting hydrophobic chemicals onto the WSGs on protein surface; 2). By interacting hydrophobic chemicals with the WSGs. For grafting, undecylenic acid (UA), a castor oil derivative with 11-carbon chain with a carboxyl group at one end and naturally hydrophobic, was used. Carboxyl groups from UA reacted with amine groups from protein and converted amines into ester with hydrophobic chains grafting on protein surface. The successful grafting of UA onto soy protein isolate (SPI) was proved by both Infrared spectroscopy (IR) and ninhydrin test. Wood adhesive made from UA modified soy protein had reached the highest wet strength of 3.30 ± 0.24 MPa with fiber pulled out, which was 65% improvement than control soy protein. Grafting fatty acid chain was verified to improve soy protein water resistance. For interaction approach, soy oil with three fatty acid chains was used to modify soy protein. Soy oil was first modified into waterborne polyurethanes (WPU) to improve its compatibility and reactivity with aqueous protein. The main forces between WPU and protein were hydrogen bonding, hydrophobic interactions, and physical entanglement. Our results showed that WPU not only increased protein surface hydrophobicity with its fatty acid chains but also enhanced the three-dimensional network structure in WPU-SPI adhesives. WPU modification had increased wet adhesion strength up to 3.81 ± 0.34 MPa with fiber pulled out compared with 2.01 ± 0.46 MPa of SPI. Based on IR and thermal behavior changes observed by DSC, it was inferred that a new crosslinking network formed between WPU and SPI. To exam if the UA and WPU technologies developed using soy protein are suitable for other plant proteins, we selected camelina protein because camelina oil has superior functional properties for jet fuels and polymers. Like soy protein, camelina protein is also highly water sensitive. However, simply applied UA and WPU to camelina protein following the same methods used for soy proteins, we did not obtain the same good adhesion results compared to what we achieved with soy protein. After protein structure analysis, we realized that camelina protein is more compact in structure compared to soy protein that made it weak in both dry and wet adhesion strength. Therefore, for camelina protein, we unfolded its compact structure with Polymericamine epichlorohydrine (PAE) first to improve flexible chains with more adhesion groups for future reaction with UA or WPU. PAE with charged groups interacted camelina protein through electrostatic interaction and promoted protein unfolding to increase reactivity within protein subunits and between protein and wood cells. Therefore, the wet adhesion strength of camelina protein was improved from zero to 1.30 ± 0.23 MPa, which met the industrial standard for plywood adhesives in terms of adhesion strength. Then the wet adhesion strength of camelina protein was further improved after applying UA and WPU into the PAE modified camelina protein. In addition, we also found PAE unfolding significantly improved the dry adhesion strength of camelina protein from 2.39 ± 0.52 to 5.39 ± 0.50 MPa with 100% wood failure on two-layer wood test. Camelina meal which is even more economical than camelina protein was studied as wood adhesive. Through a combination of PAE and laccase modification method, the wet adhesion strength of camelina meal was improved as high as 1.04 ± 0.19MPa, which also met industrial standards for plywood adhesives. The results of this study had proven successful modification of oilseed protein to increase water resistance and wet mechanical strength. We have gained in-depth understanding of the relationship between protein structure and wet adhesion strength. The successful modification of plant proteins meeting the industrial needs for bio-adhesives will promote the development of eco-friendly and sustainable materials.
24
Lougheed, Caroline. "Targeting focal adhesion signaling in cancer and acquired resistance to focal adhesion kinase inhibitors". Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=94996.
Testo completoAbstract (sommario):
In cancer progression, the development of metastases is characteristic of late stage disease and makes treatment and cure more difficult. In order for metastasis to occur, cancer cells must gain motile and invasive phenotypes. As one of the keystone proteins involved in cell motility and invasion, Focal Adhesion Kinase (FAK) has emerged as a good therapeutic target for the inhibition of metastases via targeted drug design and small molecule inhibitors. Accordingly, a small molecule inhibitor has recently been developed against FAK activation and signaling. However, drug resistance is common among targeted therapies. Development and classification of drug resistant cells elucidated the possible mechanism behind FAK inhibitor resistance such that second-line therapy drugs can be designed to overcome or avoid resistance. The overall data presented herein support the role of FAK as an important drug target in cancer metastasis as well as provide insight and direction for future FAK inhibitor design.Dans la progression du cancer, le développement de métastases est caractéristique de la phase terminale et rend le traitement difficile. Afin que des métastases se dévelopment, les cellules cancéreuses doivent acquérir de la motilité ainsi qu'un phénotype invasif. Considéré come l'une des plus importantes protéines participant dans la motilité cellulaire, la prot éine Focal Adhesion Kinase (FAK) a émergé comme une bonne cible thérapeutique pour l'inhibition de métastases par la création de drogues ciblées et de petites molécules inhibitrices. Par conséquent, une molécule inhibitrice de l'activation de FAK et sa signalisation a été récemment développée. Cependant, J'ai demontré que la résistance est commune parmis ces drogues. Le dévelopement et la classification des clones de cellules résistantes ont permi d'élucider un mécanisme impiquant en partie une amplification de l'activité FAK; ce mécanisme permetter a de découvrir des analogues de deuxième génération pour surmonter ou éviter la résistance. L'ensemble de données présentées ci-dessous supportet le rôle de FAK comme une cible importante dans la prévention de métastases et exposent les futur directions pour contourner la résistance aux inhibiteurs de FAK.
25
Horner, Alan. "Expression of porcine intercellular adhesion molecule-1 and its role in chrondrocyte-leukocyte adhesion". Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336778.
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Learn, Greg Daniel. "Towards Development of Affinity Polymer-Based Adhesion Barriers for Surgical Mesh Devices". Case Western Reserve University School of Graduate Studies / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=case1612871430445022.
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Yang, Bin [Verfasser]. "Adhesion of adhesive resin cements to dental zirconia ceramic and human dentin / Bin Yang". Kiel : Universitätsbibliothek Kiel, 2009. http://d-nb.info/1019813326/34.
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Karlsson, Anders. "Adhesion av mikroorganismer till lignocellulosa". Thesis, Mälardalen University, Mälardalen University, Department of Biology and Chemical Engineering, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-1339.
Testo completoAbstract (sommario):
The aim of the project was to develop a method to investigate differences in adhesion of microorganisms to materials that contains lignocellulose. The method was tested on a gram-positive (Micrococcus lutea) and one gram-negative (E-coliJM109) bacteria.
The study was begun by cultivation of the two microorganisms. The cultivation was done to calculate the generation times of the bacteria and to obtain growth curves. Cells from these cultivations were also frozen (-70ºC) and later used for inoculation.
At STFI-Packforsk AB the total charge on the mass was measured and later a conductivity titration on the mass was executed as well, all to find out more about the different properties of the mass. Properties that in a later part of this study could possibly be linked to the adhesion of cells to the pulp. The adhesion experiments that were executed gave poor results. The adhesion experiment with M. lutea was the only experiment that gave a reproducible result. In this experiment M. lutea was contacted with bleached leaf. A reduction of cells was observed in all of the dilutions where M. lutea had been in contact with the mass. The number of colony forming units of the culture was 1,2×107 before the adhesion and 2×106 subsequently.
29
Mizuno, Hiroyasu. "Adhesion and Nanotribology of Biofibres". Doctoral thesis, KTH, Yt- och korrosionsvetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-91312.
Testo completoAbstract (sommario):
The fibre probe atomic force microscope is developed, which allows direct measurement of force and friction between single fibres at the nanoscale under various conditions. In this work, polyester and human hair fibres were used as being representative of synthetic and animal fibre. It is shown that the forces between hair fibres and polyester fibres in solution can be well explained by a DLVO interaction and that cationic surfactants modify the interactions in a manner consistent with current views of adsorption behavior. Friction coefficients are obtained from a friction-load relationship for the fibres using Amontons’ law. The variation of friction coefficient of the synthetic fibres with surfactant concentration is well correlated with surfactant adsorption behavior. However the frictional behavior of hair is somewhat unexpected, showing a minimum in frictioncoefficient below the cmc which may be related to surfactant – protein interaction at the surface. An analysis method to distinguish fibre friction in different sliding directions is established to allow discussion of directional friction effects. In contrast to macroscopic measurements, the effect is found to be small for native hair but significant for bleached hair at most of the sliding angles. This mechanism is largely correlated with the higher surface roughness of bleached hair. In addition the friction coefficient of bleached hair is shown to change periodically with the sliding angle, associated with cuticle – cuticle interlocking. A monolayer consisting of 18-methyleicosane thiol (18-MET) is fabricated as a model surface for hair. Friction and force measurements are performed and the results compared with those of the straight chain analogue eicosane thiol (ET) monolayer to discriminate the effect of the branched methyl on 18-MET. The 18-MET monolayer shows a slightly higher surface energy due to the terminal gauche defect of the film, and this can be correlated with a loss of adhesion in MSUD (maple syrup urine disease) hair where the methyl branched surface lipids are largely replaced by the straight chain analogue. While the current view on the function of methyl branched lipids is to reduce the friction of hair, our results shows lower lubricating ability for 18-MET monolayer than that of ET monolayer and the effect may be associated with the surface roughness and film density. It is also shown that the presence of the methyl branch alters surfactant adsorption behavior to the surfaces which has an impact on boundary lubrication. The adhesion mechanisms of the components in gastroliths, a calcium carbonatedbio material from a red claw lobster, are investigated by means of colloid probe AFM. A technique employed to extract the gastrolith and thus vary the composition, enabled a systematic study on the contribution of the various components; calcium carbonate, chitin and gastrolith proteins, to the detachment behavior and adhesion energy. Sequential detachment and large adhesion energies where observed between native gastrolith substrates and colloidal probes consisting of microparticles of heavily demineralized gastrolith and calcium carbonate. The sequential detachment behavior was absent when the soluble proteins have been removed from gastrolith substrates and the adhesive energy is reduced by more than two orders of magnitude. The sacrificial bonds that provide the large adhesion energies are probably related to multifunctional gastrolith proteins that are able to bind to both chitin and calcium carbonate.QC 20120313
30
Hall, Denise K. "Factors affecting adhesion to polyolefins". Thesis, Loughborough University, 1994. https://dspace.lboro.ac.uk/2134/31958.
Testo completoAbstract (sommario):
Factors affecting the adhesion of paint to polyolefins have been studied. These include solvent pre-treatment, types of primer and their method of interaction, flame treatment and the addition of a surface migratory additive to the polyolefin. Surface analysis techniques X-ray photoelectron spectroscopy (XPS), attenuated total reflection infra-red spectroscopy (FTIR-ATR) and contact angle measurements were used along with electron microscopy, diffusion measurements and a lap shear test. Sol vent treatments were found to affect the topography of surface, as determined by atomic force microscopy, this causes a reduction in the receding contact angle of water indicating a reduced tendency for the coating to de-wet. This gives a greater joint strength. In the case of chlorinated polyolefin primers it has been shown that chain entanglement at the polymer/primer interface is an important factor determining the joint strength and can account for up to 50% of the strength in the systems studied. Chemical interaction between the polyolefin and the paint produced after flame treatment of the polyolefin improves adhesion. Factors determining migration of additives to the polymer surface have been studied. Surface migratory material has been identified but formation of weak boundary layers can lead to little or no improvement in adhesion properties. Further work is needed in this area.
31
Xu, Yaling Pelton Robert H. "Calcium carbonate adhesion in paper /". *McMaster only, 2005.
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32
Li, Tianjun. "Adhesion and dissipation at nanoscale". Phd thesis, Ecole normale supérieure de lyon - ENS LYON, 2013. http://tel.archives-ouvertes.fr/tel-00907812.
Testo completoAbstract (sommario):
In this thesis, we test some interactions involving surfaces processes at the nanometer scale. The experiments are conducted with a highly sensitive interferometric Atomic Force Microscope (AFM), achieving a resolution down to E-28m2/Hz for the measurement of deflection. Combined with original thermal noise analysis, this tool allows quantitative characterization of the mechanical response of micrometer and nanometer sized systems, such as microcantilevers or carbon nanotubes, on a large frequency range.The first part of my work deals with the viscoelasticity of the coating of AFM cantilevers. Evidenced by a 1/f thermal noise at low frequency, this phenomenon is present when a cantilever is coated with a metallic layer (gold, aluminium, platinium, etc...). Using the fluctuation dissipation theorem and Kramers Kronig relations, we extract the frequency dependance of this viscoelastic damping on a wide range of frequency (1Hz to 20kHz). We find a generic power law dependence in frequency for this dissipation process, with a small negative coefficient that depends on materials. The amplitude of this phenomenon is shown to be linear in the coating thickness, demonstrating that the damping mechanism takes its roots in the bulk of the metallic layer.The second part of my work tackles new experiments on the interaction of carbon nanotubes with flat surfaces. Using our AFM, we perform a true mechanical response measurement of the rigidity and dissipation of the contact between the nanotube and the surface, in a peeling configuration (the nanotube is partially absorbed to the substrate). The results of this protocol are in line with the dynamic stiffness deduced from the thermal noise analysis, showing an unexpected power law dependence in frequency for the contact stiffness. We suggest some possible physical origins to explain this behavior, such as an amorphous carbon layer around the nanotube.
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Gardner, M. K. "Adhesion of coatings to steel". Thesis, University of Oxford, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376908.
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Carrasco, Sabino Dora Isabel. "Adhesion-associated proteins in Drosophila". Thesis, University of Cambridge, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612142.
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Dixon, David G. "Adhesion of lacquers to tinplate". Thesis, University of Oxford, 1985. http://ora.ox.ac.uk/objects/uuid:0160cd9e-8b4b-43a8-95b6-e1bc57a34259.
Testo completoAbstract (sommario):
A set of passivated tinplates coated with organic lacquers as used for internal coatings on cans is examined. Adhesion is measured using a butt-joint test and the results of failure load and percent area lacquer removal analysed in order to grade adhesion performance. Fracture behaviour is determined by the surface structure of the tinplates where a defect distribution common to all types is identified by Weibull analysis as responsible for failure initiation. Differences in fracture behaviour seen in the mechanical test results are revealed by examination of the fracture surfaces using optical microscopy, scanning electron microscopy and X-ray photoelectron spectroscopy. The samples with good lacquer adhesion show a positive relationship between failure load and lacquer removal which is not evident in the samples with poor lacquer adhesion. The latter exhibit weak bonding between the passivation layer and tinplate and on examining those areas of fracture surface where tinplate is revealed the fracture is seen to have propagated at this interface whereas those samples with good adhesion had failed near the lacquer-passivation layer interface within the lacquer. Passivation layers are characterised using X-ray photoelectron spectroscopy and transmission electron microscopy. Differences in composition relating to specific tin oxides and chromium oxides are correlated with adhesion performance and models for the structure of passivation layers and failure mechanisms are proposed.
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Chaffey, Brian John. "The adhesion of Staphylococcus aureus". Thesis, University of Nottingham, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.306699.
Testo completo
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Burthem, John. "Hairy cell adhesion and migration". Thesis, University of Liverpool, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240394.
Testo completo
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Yildirim, Ali. "Measurement of cultured cell adhesion". Thesis, University of Bath, 1994. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.760660.
Testo completo
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Friedlander, Ronn S. (Ronn Samuel). "Bacterial adhesion in structured environments". Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/95862.
Testo completoAbstract (sommario):
Thesis: Ph. D., Harvard-MIT Program in Health Sciences and Technology, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references.
Biofilms-surface-bound communities of microbes-are a major medical concern, as they can be sources of infection that are difficult to eradicate. Their formation starts with the attachment of bacteria to available surfaces-often implantable biomaterials. The development of materials that prevent bacterial adhesion is therefore of paramount importance, and it requires a thorough understanding of the materials and bacterial surface properties that enable adhesive interactions. We herein design model surfaces and examine the interplay between micro-scale geometry, surface energy and bacterial surface properties with respect to adhesion, with the ultimate goal of understanding bacterial adhesion in structured environments, and establishing principles for design of novel surfaces that effectively repel bacteria. We first study adhesion of Escherichia coli to engineered surfaces possessing superficially unfavorable geometries. We show that cells can overcome geometric constraints with the aid of flagella, which are able to reach between narrow crevices, thus improving adhesion and expanding the range of surfaces to which cells can adhere. We examine binding of purified flagella to abiotic surfaces by means of quartz crystal microbalance (QCM) and show that flagella bind preferentially to hydrophobic surfaces, yet they do not appreciably bind to hydrophilic surfaces. Using mutant strains, we investigate the role of flagella in surface attachment of live cells and demonstrate that flagellated cells adhere best to hydrophobic substrates; however flagella may impede cell adhesion to hydrophilic surfaces. To further explore hydrophilic, structured environments with physiological relevance, we examine mucin-a natural hydrogel that typically harbors microbes in animals, while protecting the host. We purify mucins and use them in their native, three-dimensional configuration to probe bacterial swimming behavior and surface attachment in their presence. We demonstrate that mucins maintain-and possibly enhance-swimming ability for E. coli and Pseudomonas aeruginosa, and show that they greatly reduce adhesion to underlying substrates. Finally, we build on our established design principles and construct anti-adhesive surfaces by combining hydrophilic chemistries with topographic features smaller than cellular dimensions. This work suggests a path toward anti-adhesive materials that may be optimized for mechanical robustness, longevity and specific environments of application.
by Ronn S. Friedlander.
Ph. D.
40
Tsui, Yun Cheong. "Adhesion of plasma sprayed coatings". Thesis, University of Cambridge, 1996. https://www.repository.cam.ac.uk/handle/1810/283710.
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Kabiri, Farnaz Kabiri. "Gecko Adhesion on Soft Surfaces". University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1516061596336554.
Testo completo
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Shephard, Nick E. "Measuring and predicting sealant adhesion". Diss., This resource online, 1995. http://scholar.lib.vt.edu/theses/available/etd-06062008-155534/.
Testo completo
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Thomas, Wendy Evelyn. "Shear stress enhances bacterial adhesion /". Thesis, Connect to this title online; UW restricted, 2003. http://hdl.handle.net/1773/8056.
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Sarwar, Muhammad. "Measurement of mammalian cell adhesion". Thesis, University of Bath, 1992. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314527.
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Ojaghlou, Neda. "Adhesion at Solid/Liquid Interfaces". VCU Scholars Compass, 2019. https://scholarscompass.vcu.edu/etd/6079.
Testo completoAbstract (sommario):
The adhesion at solid/liquid interface plays a fundamental role in diverse fields and helps explain the structure and physical properties of interfaces, at the atomic scale, for example in catalysis, crystal growth, lubrication, electrochemistry, colloidal system, and in many biological reactions. Unraveling the atomic structure at the solid/liquid interface is, therefore, one of the major challenges facing the surface science today to understand the physical processes in the phenomena such as surface coating, self-cleaning, and oil recovery applications. In this thesis, a variety of theory/computational methods in statistical physics and statistical mechanics are used to improve understanding of water adhesion at solid/liquid interfaces. In here, we addressed two separated, but interconnected problems:
First, we consider water adhesion on fiber/surface, responsible for the emergence of droplet residue upon droplet detachment. In this project, we study the mechanism of water droplet detachment and retention of residual water on smooth hydrophilic fibers and surfaces using nonequilibrium molecular dynamics simulations. We investigate how the applied force affects the breakup of a droplet and how the minimal detaching force per unit mass decreases with droplet size. We extract scaling relations that allow extrapolation of our findings to larger length scales that are not directly accessible by molecular models. We find that the volume of the residue on a fiber varies nonmonotonically with the detaching force, reaching the maximal size at an intermediate force and associated detachment time. The strength of this force decreases with the size of the drop, while the maximal residue increases with the droplet volume, V, sub-linearly, in proportion to the V2/3.
Second, we address the adhesion on conducting graphene. We improved the graphene model by incorporating the conductivity of graphene sheet using the fluctuating charge technique of Constant Potential Molecular Dynamics (CPMD). We evaluated the wettability by measuring the contact angle of cylindrical water drops on a conducting graphene sheet. We found that the CA of a water droplet on a graphene sheet supported by water is lower than in the absence of water under graphene. Our calculations reveal effective attractions between partial charges of equal sign across the conducting graphene sheet. Attractive correlations are attributed to the formation of the highly localized image charges on carbon atoms between the partially charged sites of water molecules on both sides of graphene. By performing additional computations with nonpolar diiodomethane, we confirm that graphene transmits both polar and dispersive interactions. These findings are important in applications including sensors, fuel cell membranes, water filtration, and graphene-based electrode material to enhance the supercapacitor performance. A challenge for future work concerns dynamic polarization response of wetted graphene at alternating (AC) field condition.
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Bhasin, Amit. "Development of methods to quantify bitumen-aggregate adhesion and loss of adhesion due to water". Texas A&M University, 2003. http://hdl.handle.net/1969.1/5934.
Testo completoAbstract (sommario):
Moisture induced damage of hot mix asphalt pavements has a significant
economic impact in terms of excessive maintenance and rehabilitation costs. The
moisture sensitivity of an asphalt mix depends on the combined effects of material
properties, mixture design parameters, loading conditions and environmental factors.
Traditional methods to assess moisture sensitivity of asphalt mixes rely on mechanical
tests that evaluate the mix as a whole. These methods do not measure material properties
and their role in moisture sensitivity of the mix independently. This information is very
important to select materials resistant to moisture induced damage, or to modify locally
available materials to improve their resistance to moisture damage for economic reasons.
The objective of this research is to develop experimental and analytical tools to
characterize important material properties that influence the moisture sensitivity of
asphalt mixes.
Quality of adhesion between the aggregate and bitumen binder in wet and dry
conditions plays an important role on the moisture sensitivity of the asphalt mix. A part
of this research work was to develop the Wilhelmy plate method and the Universal
Sorption Device to measure the surface free energy components of the bitumen and
aggregate with adequate precision and accuracy, respectively. Surface energy of these
materials was used to identify parameters based on thermodynamics that can quantify
their interfacial adhesion and propensity to debond in the presence of water. The
thermodynamic parameters were shown to correlate well with the moisture sensitivity of
asphalt mixes determined from laboratory tests. Specific surface areas of the aggregates
were also used to account for the influence of mechanical interlocking at the micro scale.
In some mixes, chemical bonding also contributes to the adhesion between bitumen and aggregate. The use of a micro calorimeter was introduced in this research as a versatile
and fast tool to quantify the combined effects of physical and chemical adhesion between
these materials.
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Rincon, Troconis Brendy Carolina. "Blister Test for Measurements of Adhesion and Adhesion Degradation of Organic Polymers on AA2024-T3". The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1366072959.
Testo completo
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Chang, Tsunou. "The notched coating adhesion specimen : a fracture test for coatings and accelerated screening test for adhesion /". Thesis, This resource online, 1996. http://scholar.lib.vt.edu/theses/available/etd-11182008-063511/.
Testo completo
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Sunnick, Eva Maria. "Modell der Bildung und Stabilität von Adhäsionsclustern in biologischen Membranen". Doctoral thesis, Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2013. http://hdl.handle.net/11858/00-1735-0000-0001-BB24-2.
Testo completo
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Camps, Jean. "Mise au point d'un modele in vitro d'evaluation de la cytotoxicite des systemes adhesifs". Aix-Marseille 2, 1996. http://www.theses.fr/1996AIX21601.
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