Literatura académica sobre el tema "Degraded adhesion"
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Artículos de revistas sobre el tema "Degraded adhesion"
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Nakagawa, Ichiro, Hiroaki Inaba, Taihei Yamamura, Takahiro Kato, Shinji Kawai, Takashi Ooshima y Atsuo Amano. "Invasion of Epithelial Cells and Proteolysis of Cellular Focal Adhesion Components by Distinct Types of Porphyromonas gingivalis Fimbriae". Infection and Immunity 74, n.º 7 (julio de 2006): 3773–82. http://dx.doi.org/10.1128/iai.01902-05.
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ABSTRACT Porphyromonas gingivalis fimbriae are classified into six types (types I to V and Ib) based on the fimA genes encoding FimA (a subunit of fimbriae), and they play a critical role in bacterial interactions with host tissues. In this study, we compared the efficiencies of P. gingivalis strains with distinct types of fimbriae for invasion of epithelial cells and for degradation of cellular focal adhesion components, paxillin, and focal adhesion kinase (FAK). Six representative strains with the different types of fimbriae were tested, and P. gingivalis with type II fimbriae (type II P. gingivalis) adhered to and invaded epithelial cells at significantly greater levels than the other strains. There were negligible differences in gingipain activities among the six strains; however, type II P. gingivalis apparently degraded intracellular paxillin in association with a loss of phosphorylation 30 min after infection. Degradation was blocked with cytochalasin D or in mutants with fimA disrupted. Paxillin was degraded by the mutant with Lys-gingipain disrupted, and this degradation was prevented by inhibition of Arg-gingipain activity by Nα-p-tosyl-l-lysine chloromethyl ketone. FAK was also degraded by type II P. gingivalis. Cellular focal adhesions with green fluorescent protein-paxillin macroaggregates were clearly destroyed, and this was associated with cellular morphological changes and microtubule disassembly. In an in vitro wound closure assay, type II P. gingivalis significantly inhibited cellular migration and proliferation compared to the cellular migration and proliferation observed with the other types. These results suggest that type II P. gingivalis efficiently invades epithelial cells and degrades focal adhesion components with Arg-gingipain, which results in cellular impairment during wound healing and periodontal tissue regeneration.
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Rajshankar, Dhaarmini, Gregory P. Downey y Christopher A. McCulloch. "IL‐1β enhances cell adhesion to degraded fibronectin". FASEB Journal 26, n.º 11 (24 de julio de 2012): 4429–44. http://dx.doi.org/10.1096/fj.12-207381.
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YAMADA, Tatsuhiko, Yanhong HU y Hirokuni ONO. "Condensation Reaction of Degraded Lignocellulose during Wood Liquefaction in the Presence of PolyhydricAlcohols". Journal of The Adhesion Society of Japan 37, n.º 12 (2001): 471–78. http://dx.doi.org/10.11618/adhesion.37.471.
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Tsai, S.-W., J.-F. Fang, C.-L. Yang, J.-H. Chen, L.-T. Su y S.-H. Jan. "Preparation and Evaluation of a Hyaluronate-Collagen Film for Preventing Post-Surgical Adhesion". Journal of International Medical Research 33, n.º 1 (febrero de 2005): 68–76. http://dx.doi.org/10.1177/147323000503300106.
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Post-surgical adhesion occurs when fibrous strands of scar tissue form, leading to the abnormal joining of anatomical structures. Patients undergoing abdominal surgery are at risk of the complications associated with intraperitoneal adhesions. Hyaluronic acid (HA) is a biocompatible, biodegradable and non-toxic natural polymer, which is gaining popularity as a barrier agent for preventing post-surgical adhesions. As HA is water-soluble and rapidly degraded in vivo, chemical modification is required to produce a non-soluble sheet that might be used to prevent tissue adhesion. We developed a range of biocompatible cross-linked HA-collagen composites and then evaluated them in a rat model of post-surgical adhesion. The results showed that cross-linked HA-collagen was almost totally resistant to hyaluronidase digestion. HA-collagen membranes induced minimal tissue reactions and were bioresorbed within 14 days post-surgery. These results suggest that cross-linked HA-collagen membrane may be a valuable anti-adhesion material to prevent post-surgical intraperitoneal adhesion.
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Carragher, Neil O., Bodo Levkau, Russell Ross y Elaine W. Raines. "Degraded Collagen Fragments Promote Rapid Disassembly of Smooth Muscle Focal Adhesions That Correlates with Cleavage of Pp125FAK, Paxillin, and Talin". Journal of Cell Biology 147, n.º 3 (1 de noviembre de 1999): 619–30. http://dx.doi.org/10.1083/jcb.147.3.619.
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Active matrix metalloproteinases and degraded collagen are observed in disease states, such as atherosclerosis. To examine whether degraded collagen fragments have distinct effects on vascular smooth muscle cells (SMC), collagenase-digested type I collagen was added to cultured human arterial SMC. After addition of collagen fragments, adherent SMC lose their focal adhesion structures and round up. Analysis of components of the focal adhesion complex demonstrates rapid cleavage of the focal adhesion kinase (pp125FAK), paxillin, and talin. Cleavage is suppressed by inhibitors of the proteolytic enzyme, calpain I. In vitro translated pp125FAK is a substrate for both calpain I– and II–mediated processing. Mapping of the proteolytic cleavage fragments of pp125FAK predicts a dissociation of the focal adhesion targeting (FAT) sequence and second proline-rich domain from the tyrosine kinase domain and integrin-binding sequence. Coimmunoprecipitation studies confirm that the ability of pp125FAK to associate with paxillin, vinculin, and p130cas is significantly reduced in SMC treated with degraded collagen fragments. Further, there is a significant reduction in the association of intact pp125FAK with the cytoskeletal fraction, while pp125FAK cleavage fragments appear in the cytoplasm in SMC treated with degraded collagen fragments. Integrin-blocking studies indicate that integrin-mediated signals are involved in degraded collagen induction of pp125FAK cleavage. Thus, collagen fragments induce distinct integrin signals that lead to initiation of calpain-mediated cleavage of pp125FAK, paxillin, and talin and dissolution of the focal adhesion complex.
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Leimgruber, Simon, Wolfgang Kern, Roman Hochenauer, Michael Melmer, Armin Holzner y Gregor Trimmel. "RUBBER–BRASS ADHESION LAYER ANALYSIS USING THE OLEFIN-METATHESIS METHOD". Rubber Chemistry and Technology 88, n.º 2 (1 de junio de 2015): 219–33. http://dx.doi.org/10.5254/rct.14.85946.
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ABSTRACT The investigation of the adhesion layer between rubber and brass-coated steel wires is a challenging task due to its strong bonding. We explore the possibilities of olefin-metathesis as a method to degrade the cross-linked rubber network without destroying the adhesion layer. Using a ruthenium catalyst and 1-octene as a co-reactant, different types of rubber—natural rubber, acrylonitrile–butadiene rubber, and styrene–butadiene rubber—can be degraded into soluble fragments. The uncovered adhesion layers can be subsequently analyzed with common analytical methods such as optical microscopy, focusvariation microscopy, and scanning electron microscopy. The revealed surface structures are discussed considering the observed pull-out forces. In a second series, the influence of common additives—cobalt salt, silica, and a resin system—on the metathesis reaction is investigated.
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Clark, S. K. "Loss of Adhesion of Cord-Rubber Composites in Aircraft Tires". Tire Science and Technology 14, n.º 1 (1 de enero de 1986): 33–43. http://dx.doi.org/10.2346/1.2148764.
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Abstract The degradation of adhesive strength between plies in aircraft tires was studied as a function of aging temperature, time, and environment. Adhesive strength degraded much faster than the cord tensile strength under the aging conditions used. Adhesive strength degraded faster in air than in nitrogen during the long-term aging. A 50% loss in adhesive strength is suggested as a reasonable critical value in determining tire life.
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Demetrescu, Ioana, D. Iordachescu, D. Ionita y Stef Manea. "Surface Analysis and Cell Biology Technique in Understanding Degradation of Natural Temporary Teeth Collected from an Area with High Pollution". Key Engineering Materials 396-398 (octubre de 2008): 35–38. http://dx.doi.org/10.4028/www.scientific.net/kem.396-398.35.
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The aim of this paper is to correlate surface features of degraded temporary teeth from area with high pollution with the cell adhesion and proliferation. Viability of gingival fibroblast (HGF-1, CRL-2014, American Type Culture Collection) was evaluated with a MTT (3-(4,5-dimetiltiazol-2-il)-2,5-difeniltetrazolium bromide ) test and the values are discussed for the most degraded temporary teeth in correlation with the change in surface morphology and hydrophilic/hydrophobic balance, taking into account that cell adhesion is related to a more hydrophilic character.
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MAlvezzi, M., B. Allotta y L. Pugi. "Feasibility of degraded adhesion tests in a locomotive roller rig". Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit 222, n.º 1 (enero de 2008): 27–43. http://dx.doi.org/10.1243/09544097jrrt108.
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Huang, Xuhui, Ciaron Hamilton, Zonglin Li, Lalita Udpa, Satish S. Udpa y Yiming Deng. "Capacitive imaging for adhesive bonds and quality evaluation". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 378, n.º 2182 (14 de septiembre de 2020): 20190590. http://dx.doi.org/10.1098/rsta.2019.0590.
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Defective adhesive bonds pose significant threats towards structural integrity due to reduced joint strength. The nature of the adhesion of two solids remains poorly understood since the adhesion phenomenon is relevant to so many scientific and technological areas. A concept that has been gaining our attention from the perspective of non-destructive testing is the properties discontinuity of the adhesion. Discontinued properties depend significantly on the quality of the interface that is formed between adhesive and substrate. In this research, discontinued electrical properties at the interface are considered. The simplified model is free from multidisciplinary knowledge of chemistry, fracture mechanics, mechanics of materials, rheology and other subjects. From a practical standpoint, this emphasizes the need to establish a good relationship between electrical properties of adhesive bonds and corresponding measurements. Capacitive imaging (CI) is a technique where the dielectric property of an object is determined from external capacitance measurements. Thus, it is potentially promising since adhesive and substrate differ in terms of dielectric property. At the interface between adhesive and substrate, discontinuity of the dielectric properties causes abrupt changes in electric field spatial distribution and thus alters capacitance measurement by simulating defects in adhesive joints regarding permittivity uncertainties. Further understanding of the cause of degraded adhesion quality can be obtained. This article is part of the theme issue ‘Advanced electromagnetic non-destructive evaluation and smart monitoring’.
Tesis sobre el tema "Degraded adhesion"
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Meacci, Martina. "Development and Validation of Innovative Adhesion Models for Railway Applications". Doctoral thesis, 2020. http://hdl.handle.net/2158/1205840.
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Datla, Naresh Varma. "Fatigue Behavior in Hygrothermally Degraded toughened epoxy Adhesives". Thesis, 2011. http://hdl.handle.net/1807/29700.
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A method to measure the mixed-mode fatigue behavior of environmentally degraded adhesive joints was developed. Firstly, the absorption and desorption of water in two different rubber-toughened epoxy adhesives was measured gravimetrically. The water absorption in both adhesives showed anomalous behavior that was fitted to a new “sequential dual Fickian” (SDF) model. The water desorption in both adhesives was modelled accurately using Fick’s law, and there was a significant difference in the amount of retained water after drying in the two adhesives.
The effects of long-term aging were studied using open-faced specimens made with two different rubber-toughened epoxy adhesives. The contrasting results illustrated the effects of environmental degradation on the matrix and toughener. Furthermore, the differences in the degradation behavior of both adhesives, combined with gravimetric and dynamic mechanical thermal analysis (DMTA) results, were used to illustrate the role of retained water in degrading the toughening mechanisms. The measured fatigue results invalidated the environmental index (EI) hypothesis for fatigue behavior, at least for the relatively short aging times studied here. Compared with aging under constant humidity, the fatigue performance of joints was found to be superior after aging in a cyclic salt-spray environment due to the lower water concentrations in the adhesive.
The effects of test environment humidity and temperature on the fatigue behavior were also studied using closed, un-aged specimens. Both individual and combined effects of temperature and humidity on fatigue behavior were studied. In elevated temperature and humidity environment, joint performance at higher crack growth rates was degraded solely due to the effect of the increased temperature, whereas fatigue performance at low crack growth rates degraded predominantly because of elevated moisture.
Finally, to generalise the techniques developed to automotive aluminum sheets, a reinforced specimen was developed that avoids yielding of thin aluminum sheet adherends while loading. Fatigue testing with these reinforced specimens revealed that the fatigue behavior was sensitive to the loading phase angle and the orientation of rolling lines on the sheet. These reinforced specimens were also used to study the effects of long-term aging and the effects of test environment.
Capítulos de libros sobre el tema "Degraded adhesion"
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Hantaï, D. y B. W. Festoff. "Adhesive Basement Membrane (BM) Proteins are Degraded by Plasminogen Activator in the Presence of Plasminogen". En Proceedings in Life Sciences, 167–71. Berlin, Heidelberg: Springer Berlin Heidelberg, 1986. http://dx.doi.org/10.1007/978-3-642-70690-5_33.
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"Adhesive Joints and the Environment". En Adhesion Science, 134–49. 2a ed. The Royal Society of Chemistry, 2021. http://dx.doi.org/10.1039/bk9781788018883-00134.
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Adhesives can be chemically degraded by oxygen and UV, and additives can be used to reduce this. Temperature fluctuations can introduce stresses to large bonded areas, such as panels on buildings. Water is the real villain as it is ubiquitous and attacks structural adhesive joints. Adhesives transmit water to the interface and there is a number of views on how it causes weakening. There is strong evidence for a critical humidity, below which there is no weakening.
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Huang, Xuhui, Ciaron Hamilton, Zonglin Li, Lalita Udpa, Satish S. Udpa y Yiming Deng. "Capacitive Imaging for Adhesive Bonds and Quality Evaluation". En Studies in Applied Electromagnetics and Mechanics. IOS Press, 2020. http://dx.doi.org/10.3233/saem200010.
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Defective adhesive bonds pose significant threats towards structural integrity due to reduced joint strength. While the nature of the adhesion of two solids remains poorly understood since adhesion phenomenon is relevant to so many scientific and technological areas. A concept that has been gaining our attention from the perspective of nondestructive testing is the properties discontinuity of the adhesion. Discontinued properties depend significantly on the quality of the interface that is formed between adhesive and substrate. In this research, discontinued electrical properties at the interface are considered. The simplified model is free from multidisciplinary knowledge of chemistry, fracture mechanics, mechanics of materials, rheology and other subjects. From a practical standpoint, this emphasizes the need to establish a good relationship between electrical properties of adhesive bonds and corresponding measurements. Capacitive Imaging (CI) is a technique where the dielectric property of an object is determined from external capacitance measurements. Thus, it is potentially promising since adhesive and substrate differ in terms of dielectric property. At the interface between adhesive and substrate, discontinuity of the dielectric properties causes abrupt changes in electric field spatial distribution and thus alters capacitance measurement. By simulating defects in adhesive joints regarding permittivity uncertainties. Further understanding of the cause of degraded adhesion quality can be obtained
Actas de conferencias sobre el tema "Degraded adhesion"
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Frea, Matteo y Luc Imbert. "Safe Deceleration Recovery in Degraded Braking Conditions". En EuroBrake 2021. FISITA, 2021. http://dx.doi.org/10.46720/3308473eb2021-ibc-009.
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With new technological breakthroughs come new challenges for all the actors across that same industry, and this can be said for the Automatic Train Operation in the railway industry. This new way of operating trains increases the need for safe monitoring and management of the train’s braking performance. The future brake systems are expected to reliably and predictably perform an emergency braking therefore ensuring a high accuracy of the train’s stopping distance. To satisfy the need of the upcoming market, a new solution and method is proposed allowing to mitigate and compensate for degraded conditions, whether they are linked to environmental conditions (such as low wheel rail adhesion conditions) or failures of on-board equipment. The solution is based on the safe monitoring of the train deceleration and the safe management of the braking force allowing the new brake system to reach the targets of reliability and predictability of the emergency braking. This solution is based on research and technologies developed in the frame of the Shift2Rail program (PINTA, PINTA2 and PIVOT2 projects), where Faiveley/Wabtec is fully engaged developing a new generation of adhesion management systems. Dedicated experimentations in relevant environment have shown promising signs on the reliability of the braking distance compared to the traditional systems.
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Allotta, B., R. Conti, E. Meli, L. Pugi y A. Ridolfi. "Development of a full-scale roller-rig to test high speed trains under degraded adhesion conditions". En 2014 IEEE/ASME 10th International Conference on Mechatronic and Embedded Systems and Applications (MESA). IEEE, 2014. http://dx.doi.org/10.1109/mesa.2014.6935542.
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Kuroda, S., J. Kawakita, T. Fukushima y S. Tobe. "Importance of the Adhesion of HVOF Sprayed Coatings for Aqueous Corrosion Resistance". En ITSC2001, editado por Christopher C. Berndt, Khiam A. Khor y Erich F. Lugscheider. ASM International, 2001. http://dx.doi.org/10.31399/asm.cp.itsc2001p1123.
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Abstract Importance of coating adhesion in a corrosive environment was studied experimentally. Tensile adhesion strength of HVOF sprayed 316L stainless steel and Hastelloy C coatings were tested in as-sprayed condition as well as after immersion in seawater. It was found that the adhesion strength of the stainless steel coatings degraded rapidly whereas that of the Hastelloy coatings remained almost intact. Specimens with an artificial defect were also immersed in seawater. The cross sectional observation after the test revealed that the corrosion at the coating-substrate interface proceeded much faster with the stainless steel coating as compared to the Ni-base alloy coating. A model experiment to simulate the galvanic corrosion of a coating-substrate couple was carried out and no significant difference in the galvanic current density was found between the two coatings when coupled with the steel substrate. The tightness of the coating-substrate interface was then tested with a fluorescent dye penetration test. The dye could penetrate the boundary between the stainless steel coating and the substrate whereas the boundary between the Ni-base alloy coating and the substrate was so tight that no penetration occurred. The size of the micro-gaps at the coating-substrate boundary was discussed from the viewpoint of classical Washburn-Ridiel theory. It was concluded that such micro-gaps between the coating and substrate must be eliminated for these barrier-type coatings to be used in corrosive environments. Heat treatment was highly effective for suppressing the preferential corrosion at the coating-substrate boundary.
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Maruyama, T., T. Kobayashi, K. Tsujimoto, K. Tani y K. Tanaka. "Residual Grit on the Substrate Surface in Roughening Treatment: Quantitative Evaluation and a Reduction Technique". En ITSC2005, editado por E. Lugscheider. Verlag für Schweißen und verwandte Verfahren DVS-Verlag GmbH, 2005. http://dx.doi.org/10.31399/asm.cp.itsc2005p1393.
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Abstract Generally, the surface of a substrate is roughened by blasting in pretreatment thermal spraying. Since some of the grit remains on the substrate surface, sprayed coating and the adhesion property characteristics are degraded. However, it seems that there is almost no research on this problem. In this study, residual grit is quantitatively evaluated, and a technique for reducing grit is proposed. For residual grit reduction, a solid lubricant was used, and applied to the surface of a substrate or grit; reduction of residual grit was confirmed. After blasting with solid lubricant, it remained on the substrate surface, which could be removed by heating the substrate.
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Almalki, Ahmed, Ali Rajhi, Hussam Noor, Animesh Kundu y John Coulter. "Experimental Investigation of the Robustness of Bulk Metallic Glass-Based Tooling for Microinjection Molding". En ASME 2022 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/imece2022-94888.
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Abstract The primary objective of this research was to experimentally investigate the robustness of a commercially available zirconium-based bulk metallic glass material (Zr-based BMG) for microinjection molding (μIM) tooling. The focused ion beam (FIB) direct milling process was utilized to fabricate microfeatures onto two BMG-based mold inserts. Uncoated and Ti-coated inserts were inspected through molding cycles utilizing SEM. Additionally, TPU molded samples were characterized to quantify the replication quality of the inserts through molding cycles. This is to understand the polymer melt effect of the tooling during molding conditions. The uncoated BMG insert was utilized for more than 1000 molding cycles regardless of the potential crystallization. No signs of any crack initiation were observed in any part of the BMG insert. Through molding process, the replication quality degraded due to the polymer adhesion to the microcavity base. In the case of the coated BMG insert, the coating could not withstand the high ejection force during demolding stage. The adhesion between the coating and the BMG surface was insufficient to survive molding conditions. This resulted in disintegrated coating that was bonded into molded samples.
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Gupta, Vijay, Robert Hernandez, Rajen Dias, Vasudeva Atluri, George Raiser, Mike Mello, Lars Skoglund y Paul Zimmerman. "Measurement of Interfacial Adhesion and its Degradation in Multi-Layer Packages, Devices, and Blanket Films Using the Laser Spallation Technique". En ISTFA 2000. ASM International, 2000. http://dx.doi.org/10.31399/asm.cp.istfa2000p0025.
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Abstract A laser spallation technique to measure the tensile strength of thin film interfaces is introduced. In this technique, a laser-generated stress wave of nanosecond duration in the substrate spalls off (completely removes) a coating deposited on the substrate’s front surface. The threshold laser energy is converted into the tensile stress (strength) at the failure site (usually the interface) by using an optical interferometer. Because of the ultra-short duration of the stress wave loading, all plastic deformation processes that usually accompany the coating decohesion event are suppressed such that the measured value can be regarded as fundamental or intrinsic to the material system (including the defects, if any). Application of this technique to test planar as well geometrically heterogeneous interfaces in IC’s, substrates, and packages is demonstrated. The technique is used to quantify the degrading effects of moisture and in-situ temperature rise on the tensile strength of a polyimide/Si3N4/Si interface system whose strength was systematically degraded by exposing the samples to controlled humidity (50-70% RH) conditions for varying duration (12-96 hrs) and temperatures (30°C-150°C). These measurements of strength degradation can now be used to predict device reliability from a fundamental standpoint in conjunction with simulations capable of predicting time-dependent stress concentrations, moisture accumulation, and temperature rise at critical interfaces during processing and service environment in actual systems.
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Tomotani, Miki, Hiroshi Ashida, Yasuyuki Goto y Seigen Otani. "Evaluation of Pt/PZT/Pt Capacitors Using SIMS". En ISTFA 1998. ASM International, 1998. http://dx.doi.org/10.31399/asm.cp.istfa1998p0185.
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Abstract Ferro-electric thin film materials have been used for nonvolatile random access memories(FRAM*). PZT(Pb(Ti,Zr)O3) is one of several promising materials for use as a FRAM capacitor in combination with a platinum film as an electrode. However the ferroelectric properties of this capacitor are degraded by commonly used LSI processes, such as a passivation/ insulator(CVD-SiO2) process. Recently, mechanisms of process degradation are being investigated**,***, but are not clearly understood yet. For example, to our knowledge the existence of hydrogen in the capacitor after an annealing in hydrogenous atmosphere has not yet been measured by analytical methods. As a result in this study, we measured electrical properties of Pt/PZT/Pt capacitors after a 7.6 torr N2-H2 annealing at various hydrogen partial pressures and temperatures. Then we measured composition profiles of these capacitors by Secondary Ion Mass Spectrometry(SIMS). We found that after the N2-H2 annealing, the non-volatile polarization(Pnv)(uC/cm2) of the capacitors rapidly decreased under the presence of hydrogen at lower temperatures. At the same time, SIMS profiles showed that hydrogen concentration increased in the PZT film, and oxygen concentration decreased in the upper Pt film. We considered that the increase of hydrogen in the PZT film causes the degradation of electric properties, and the decrease of oxygen in the Pt film makes the adhesion force between the upper platinum electrode and the PZT film weaker. Moreover we found that the degradation can be eliminated by annealing in oxygen at temperatures as high as 400 °C.
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Pötzsch, B., U. Delvos, E. Anders, N. Heimburger y G. Müller-Berghaus. "FACTOR VIII/VON WILLEBRAND FACTOR COMPLEX: ONLY THE 440 000 SUBUNIT OF ENDOTHELIAL CELL-DERIVED VON WILLEBRAND FACTOR FORMS A COMPLEX WITH PURIFIED PLASMA FACTOR VIIIC". En XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1644092.
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Von Willebrand Factor (vWF) circulates in plasma as a series of multimers with moleculag weight ranging from M = 0.44 x 106 up to more than 20 x 106 . Besides the mediation of platelet adhesion to exposed subendothelium, the protein plays an important role in the stabilization and the transport of Factor VIIIC (FVIIIC). In the present study the interaction between FVIIIC and vWF was studied by recombination experiments. vWF was isolated from cultured human umbilical vein endothelial cells by immunoprécipitation. This source of vWF ascertained, that it was free of FVIIIC as indicated by the absence of FVIIIC activity as well as FVIIIC antigen. FVIIIC was prepared by immunoabsorption from human plasma yielding an activity of 1600 IJ/mg. SDS-PAGE analysis showed two main bands at Mr= 0.28 x 106 and 0.18 x 106 , respectively. vWF-multimers were separated by SDS agarose gel electrophoresis and were electrophoretically transferred onto nitrocellulose sheets. After extensive washing, the sheets were incubated for 12 h with 20 U/ml FVIIIC in PBS, pH 7.4, containing 2.5 mM calcium chloride. Subsequently, associated FVIIIC was detected by autoradiography with a 125-I-labelled monoclonal mouse anti-(human FVIIIC) antibody. The results of recombination experiments exclusively showed prominent staining of the Mr= 0.44 x 106 vWF band in the autoradiography. However, proteolytically degraded FVIIIC with partly retained procoagulant activity did not show a positive stain. The results indicate that an intact FVIIIC molecule and the smallest multimer of vWF are required for the formation of a stable FVIII/vWF complex.
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Sourisseau, Quentin, Emilie Leprêtre, Sylvain Chataigner, Xavier Chapeleau, Luc Mouton y Stéphane Paboeuf. "Adhesively Bonded FRP Reinforcement of Steel Structures: Surface Preparation Analysis and Influence of the Primer". En ASME 2022 41st International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/omae2022-79079.
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Abstract In tropical areas, with marine environment, high temperature and humidity, corrosion is a constant threat. The maintenance of steel structures (like FPSO’s) is becoming a challenge. The current technique of “crop and renewing” repair involves a certain number of major issues for project owners such as: “hot work”, that is to say welding; temporary weakening of the structure; need to empty, clean and purging the oil tanks of the FPSO’s, resulting in long downtime and an expensive solution. “Cold repair”, such as composite repair, is a promising solution. However, surface preparation and the influence of the primer are crucial issues to be addressed to ensure the strength and reliability of this type solution based on bonded patch. The paper presents an experimental study of the influence of the surface preparation and the primer on the strength of small steel bonded specimens which have been deliberately degraded by corrosion and pollution. Several surface preparation methodologies were investigated and the quality of these preparations was assessed using methods that can be implemented on site. Two main aspects were investigated: the detection of the residual presence of pollutants through the use of a portable infrared spectrometer; and the determination of surface energy after preparation using contact angle and wettability measurement equipment. To study the impact of the primer on the adhesion capacity of the steel surface, critical toughnesses measurements was performed with End notch flexure tests. Three configurations have been tested: bonding with the epoxy resin without initial application of primer and bonding with the Epoxy resin with initial application of two Primer A and B. The results shown clearly that the type of primer and the quality of its application are paramount importance to ensure the strength of steel bonded patches.
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Beteta, Alan, Lorraine Boak, Katherine McIver, Myles Jordan y Robin Shields. "Mechanistic Understanding of the Impact of EOR Polymer on the Inhibition Mechanism and Performance of Phosphonate Scale Inhibitors". En SPE International Conference on Oilfield Chemistry. SPE, 2021. http://dx.doi.org/10.2118/204383-ms.
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Abstract With the current trend for application of Enhanced Oil Recovery (EOR) technologies, there has been much research into the possible upsets to production, from the nature of the produced fluids to changes in the scaling regime. The key question being addressed in this publication is the influence of EOR chemicals, such as hydrolyzed polyacrylamide (HPAM), on scale inhibitor (SI) squeeze lifetime for barium sulphate and calcium carbonate scale risk. Squeeze lifetime is defined as the duration of time (or produced water volume) before the minimum inhibitor concentration (MIC) is reached. This is controlled by the adsorption, and later release, of the inhibitor onto the reservoir rock and the MIC of the inhibitor selected for the produced brine. This paper builds on earlier published work investigating potential changes to inhibitor adsorption caused by polymer EOR produced and moves to the evaluation of the changes in MIC due to the presence of EOR chemical. In the static inhibitor performance bottle tests, the EOR polymer alone appeared to show some degree of inhibition performance against BaSO4, but below a level required for effective scale management. However, in combination with the inhibitor (DETPMP) at near MIC levels, the inhibition efficiency was negatively impacted by the presence of degraded HPAM EOR polymer. During dynamic tube blocking tests, the inclusion of even low levels of HPAM (2.5 ppm) were shown to reduce the differential pressure build up suggesting barite scale inhibition or reduced adhesion to the coil. Furthermore, the scale morphology produced in these tests, examined under a scanning electron microscope, was clearly impacted in the presence of HPAM. For the CaCO3 system there appears to be increasing positive impact from HPAM on CaCO3 morphology with HPAM concentration and, as observed for BaSO4, an improved performance in dynamic efficiency experiments. However, at higher HPAM concentrations (500 ppm) the precipitate was amorphous and only a minor pressure rise was observed during the tube blocking experiments. From these observations, it is clear that HPAM can impact the way both calcite and barite scale grow, especially at lower inhibitor concentrations (<MIC) and hence impacts the mechanism by which DETPMP can function to prevent scale nucleation and growth. This study represents a comprehensive review of both inhibition performance in the presence of an EOR polymer and with these findings the implication to field treatment lifetimes and associated costs of scale management via scale squeeze in a field under HPAM flooding.
Informes sobre el tema "Degraded adhesion"
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Morrison, Mark y Joshuah Miron. Molecular-Based Analysis of Cellulose Binding Proteins Involved with Adherence to Cellulose by Ruminococcus albus. United States Department of Agriculture, noviembre de 2000. http://dx.doi.org/10.32747/2000.7695844.bard.
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At the beginning of this project, it was clear that R. albus adhered tightly to cellulose and its efficient degradation of this polysaccharide was dependent on micromolar concentrations of phenylacetic acid (PAA) and phenylpropionic acid (PPA). The objectives for our research were: i) to identify how many different kinds of cellulose binding proteins are produced by Ruminococcus albus; ii) to isolate and clone the genes encoding some of these proteins from the same bacterium; iii) to determine where these various proteins were located and; iv) quantify the relative importance of these proteins in affecting the rate and extent to which the bacterium becomes attached to cellulose. BARD support has facilitated a number of breakthroughs relevant to our fundamental understanding of the adhesion process. First, R. albus possesses multiple mechanisms for adhesion to cellulose. The P.I.'s laboratory has discovered a novel cellulose-binding protein (CbpC) that belongs to the Pil-protein family, and in particular, the type 4 fimbrial proteins. We have also obtained genetic and biochemical evidence demonstrating that, in addition to CbpC-mediated adhesion, R. albus also produces a cellulosome-like complex for adhesion. These breakthroughs resulted from the isolation (in Israel and the US) of spontaneously arising mutants of R. albus strains SY3 and 8, which were completely or partially defective in adhesion to cellulose, respectively. While the SY3 mutant strain was incapable of growth with cellulose as the sole carbon source, the strain 8 mutants showed varying abilities to degrade and grow with cellulose. Biochemical and gene cloning experiments have been used in Israel and the US, respectively, to identify what are believed to be key components of a cellulosome. This combination of cellulose adhesion mechanisms has not been identified previously in any bacterium. Second, differential display, reverse transcription polymerase chain reaction (DD RT-PCR) has been developed for use with R. albus. A major limitation to cellulose research has been the intractability of cellulolytic bacteria to genetic manipulation by techniques such as transposon mutagenesis and gene displacement. The P.I.'s successfully developed DD RT- PCR, which expanded the scope of our research beyond the original objectives of the project, and a subset of the transcripts conditionally expressed in response to PAA and PPA have been identified and characterized. Third, proteins immunochemically related to the CbpC protein of R. albus 8 are present in other R. albus strains and F. intestinalis, Western immunoblots have been used to examine additional strains of R. albus, as well as other cellulolytic bacteria of ruminant origin, for production of proteins immunochemically related to the CbpC protein. The results of these experiments showed that R. albus strains SY3, 7 and B199 all possess a protein of ~25 kDa which cross-reacts with polyclonal anti-CbpC antiserum. Several strains of Butyrivibrio fibrisolvens, Ruminococcus flavefaciens strains C- 94 and FD-1, and Fibrobacter succinogenes S85 produced no proteins that cross-react with the same antiserum. Surprisingly though, F. intestinalis strain DR7 does possess a protein(s) of relatively large molecular mass (~200 kDa) that was strongly cross-reactive with the anti- CbpC antiserum. Scientifically, our studies have helped expand the scope of our fundamental understanding of adhesion mechanisms in cellulose-degrading bacteria, and validated the use of RNA-based techniques to examine physiological responses in bacteria that are nor amenable to genetic manipulations. Because efficient fiber hydrolysis by many anaerobic bacteria requires both tight adhesion to substrate and a stable cellulosome, we believe our findings are also the first step in providing the resources needed to achieve our long-term goal of increasing fiber digestibility in animals.