985 resultados para Adhesive joints
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Bacterial adhesion to other bacteria, to eukaryotic cells, and to extracellular matrix proteins is frequently mediated by cell surface-associated polymers (fimbriae) consisting of one or more subunit proteins. We have found that polymerization of curlin to fimbriae-like structures (curli) on the surface of Escherichia coli markedly differs from the prevailing model for fimbrial assembly in that it occurs extracellularly through a self-assembly process depending on a specific nucleator protein. The cell surface-bound nucleator primes the polymerization of curlin secreted by the nucleator-presenting cell or by adjacent cells. The addition of monomers to the growing filament seems to be driven by mass action and guided only by the diffusion gradient between the source of secreted monomer and the surface of monomer condensation.
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The present paper addresses the analysis of structural vibration transmission in the presence of structural joints. The problem is tackled from a numerical point of view, analyzing some scenarios by using finite element models. The numerical results obtained making use of this process are then compared with those evaluated using the EN 12354 standard vibration reduction index concept. It is shown that, even for the simplest cases, the behavior of a structural joint is complex and evidences the frequency dependence. Comparison with results obtained by empirical formulas reveals that those of the standards cannot accurately reproduce the expected behavior, and thus indicate that alternative complementary calculation procedures are required. A simple methodology to estimate the difference between numerical and standard predictions is here proposed allowing the calculation of an adaptation term that makes both approaches converge. This term was found to be solution-dependent, and thus should be evaluated for each structure.
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Rock mass characterization requires a deep geometric understanding of the discontinuity sets affecting rock exposures. Recent advances in Light Detection and Ranging (LiDAR) instrumentation currently allow quick and accurate 3D data acquisition, yielding on the development of new methodologies for the automatic characterization of rock mass discontinuities. This paper presents a methodology for the identification and analysis of flat surfaces outcropping in a rocky slope using the 3D data obtained with LiDAR. This method identifies and defines the algebraic equations of the different planes of the rock slope surface by applying an analysis based on a neighbouring points coplanarity test, finding principal orientations by Kernel Density Estimation and identifying clusters by the Density-Based Scan Algorithm with Noise. Different sources of information —synthetic and 3D scanned data— were employed, performing a complete sensitivity analysis of the parameters in order to identify the optimal value of the variables of the proposed method. In addition, raw source files and obtained results are freely provided in order to allow to a more straightforward method comparison aiming to a more reproducible research.
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"To build an ice-house": p. [57]-58.
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"Originally written as a series of articles for ʻThe Railway Newsʾ, in which they appeared at various periods between the years 1911 and 1914."--Pref.
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Mode of access: Internet.
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Mode of access: Internet.
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"AD no. 452191."
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Bibliography: p. 149.
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Cover title.
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Mode of access: Internet.
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Mode of access: Internet.
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"August 1965."
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Mode of access: Internet.