Adhesion mechanics

Another example of static SIMS used in a more quantitative role is in the analysis of extmded polymer blends. The morphology of blended polymers processed by extrusion or molding can be affected by the melt temperature, and pressure, etc. The surface morphology can have an effect on the properties of the molded polymer. Adhesion, mechanical properties, and physical appearance are just a few properties affected by processing conditions. 

A multilayer-type structure probably due to cords in the molten zone between single arc sprayed (0.25 MPa) Ni droplets and steel substrate were found in AES point depth profiles [2.158]. That particular arc spraying condition turned out to yield the best adhesion. Plasma-sprayed AI2O3 layers separated from pre-oxidized Ni Substrate had a micrometer-thick NiO layer on the substrate-sided face and micrometer-deep oxide interdiffusion [2.159]. In this work also, AES point depth profiling substantiated technological assumptions about adhesion mechanisms. 

Depth-sensing nanoindentation is one of the primary tools for nanomechanical mechanical properties measurements. Major advantages to this technique over AFM include (1) simultaneous measurement of force and displacement (2) perpendicular tip-sample approach and (3) well-modeled mechanics for dynamic measurements. Also, the ability to quantitatively infer contact area during force-displacement measurements provides a very useful approach to explore adhesion mechanics and models. Disadvantages relative to AFM include lower force resolution, as well as far lower spatial resolution, both from the larger tip radii employed and a lack of sample positioning and imaging capabilities provided by piezoelectric scanners. 

Fillers may be broadly defined as solid particulates or fibrous materials, substantially inert chemically, incorporated in polymer compositions to modify the properties and/or to reduce cost. Cost reduction is not the primary reason to incorporate fillers in adhesives but they are used to impart specific properties such as flow, improved adhesion, mechanical, thermal, electrical and optical properties, chemical and weather resistance, and rheological behaviour. 

Jones, F.R., Interfacial aspects of glass fibre reinforced plastics. In Jones, F.R. (Ed.), Interfacial Phenomena in Composite Materials. Butterworths, London, 1989, pp. 25-32. Chaudhury, M.K., Gentle, T.M. and Plueddemann, E., Adhesion mechanism of poly(vinyl chloride) to silane primed metal surfaces. J. Adhes. Sci. Technol, 1(1), 29-38 (1987). Gellman, A.J., Naasz, B.M., Schmidt, R.G., Chaudhury, M.K, and Gentle, T.M., Secondary neutral mass spectrometry studies of germanium-silane coupling agent-polymer interphases. J. Adhes. Sci. Technol., 4(7), 597-601 (1990). 

Mechanical adhesion. Mechanical interlocking between the two substrates can also contribute to adhesion. This mechanism would function most effectively with fibers with rough surfaces and irregular or non-circular cross-sectional shapes. 

In any given system all of the above adhesion mechanisms are probably occurring to varying degrees. In certain systems one or another of the mechanisms can play a greater role [14]. 

Adhesion, mechanical Bonding between two surfaces caused by interlocking action of molecules. 

Interference with specific cell-cell and cell-matrix adhesion mechanisms is another rapidly advancing approach to therapeutically interfere with angiogenesis. Antagonistic antibodies (Vitaxin) to the integrin heterodimer av 33 have been shown to act on the blood vessels of tumors but not on the resting organ vasculature. Vitaxin demonstrated some promise in Phase II clinical trials. 

TABLE 1 Single Chemical Bond Forces (in pN) for Every Tip-Substrate Combination, Calculated on the Basis of the JKR Theory of Adhesion Mechanics ... 

Boggon, T. J., Murray, J., Chapuis-Flament, S., Wong, E., Gumbiner, B. M. and Shapiro, L. C-cadherin ectodomain structure and implications for cell adhesion mechanisms. Science 296(5571) 1308-1313, 2002... 

ADHESION MECHANISMS INVOLVED IN INFLUENZA VIRUS AND RELATED MICROBIAL INFECTIONS... 

Many bacterial adhesins and host receptors have been identified and studied in great depth, as described in Section VII. Therefore, with every new adhesin or receptor discovered, a new opportunity arises to develop an anti-adherence mechanism that may inhibit or block the adhesin-receptor interaction, which is the ultimate aim of anfi-adhesion therapy (Kahane and Ofek, 1996 Moricouf et ah, 1990 Ofek and Doyle, 1994). In actual practice, there are several t) es of anfi-adhesive mechanisms including adhesin-based vaccines, innafe hosf-derived anti-adhesives, probiotics, adhesin analogs, and receptor analogs. 

Research aimed at imderstanding bacterial pathogenesis has established the importance of bacterial adherence in disease. This research has led to the identification of a number of both bacterial adhesins and potential host cell receptors. By imderstanding the detailed interactions between a bacterial adhesin and host receptor, it is possible to develop new mechanisms to prevent bacterial adhesion, thereby averting disease. Many promising anti-adhesion mechanisms have been developed and studied, but much more work is needed, both in vitro and in vivo, to establish the feasibility of these mechanisms. 

Baier, R.E., Shafrin, E.G., and Zisman, W.A., Adhesion mechanisms that assist or impede... 

Gould, J. Northcote, D. H. In Bacterial Adhesion Mechanisms and Physiological Significance Plenum New York, 1984 89-110. 

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