The Experts below are selected from a list of 792165 Experts worldwide ranked by ideXlab platform
K Simon Y Ng - One of the best experts on this subject based on the ideXlab platform.
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influence of silicone surface roughness and Hydrophobicity on adhesion and colonization of staphylococcus epidermidis
Journal of Biomedical Materials Research Part A, 2009Co-Authors: Haiying Tang, Xuemei Liang, Anfeng Wang, Steven O Salley, James P Mcallister, K Simon Y NgAbstract:Bacterial adhesion and colonization are complicated processes that depend on many factors, including surface chemistry, Hydrophobicity, and surface roughness. The contribution of each of these factors has not been fully elucidated because most previous studies used different polymeric surfaces to achieve differences in properties. The objective of this study was to modify Hydrophobicity and roughness on one polymeric surface, eliminating the confounding contribution of surface chemistry. Mechanically assembled monolayer (MAM) preparation methods (both one- and two-dimensional) were used to impart different degrees of Hydrophobicity on fluoroalkylsilane (FAS)-coated silicone. Surface roughness was varied by casting the silicone to templates prepared with different abrasives. Surface Hydrophobicity was determined by contact angle measurement, whereas surface roughness was determined by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Bacterial adhesion and colonization were analyzed using a direct colony-counting method and SEM images. Hydrophobicity increased as a function of stretched length or width (Δx or Δy); it reached a maximum at Δx = 60% with one-dimensional MAM and decreased as Δx further increased to 80 and 100%. The same trend was observed for the two-dimensional MAM. After 12-h incubation, all the FAS/silicone surfaces had significantly reduced adherence of Staphylococcus epidermidis by 42–89%, compared to untreated silicone, and the degree of which is inversely related to surface Hydrophobicity. On the other hand, surface roughness had a significant effect on bacterial adhesion and colonization only when the root-mean-square roughness was higher than 200 nm. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res 2009
Ulf W Gedde - One of the best experts on this subject based on the ideXlab platform.
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Hydrophobicity changes in silicone rubbers
IEEE Transactions on Dielectrics and Electrical Insulation, 1999Co-Authors: Henrik Hillborg, Ulf W GeddeAbstract:Water repellency, high surface resistivity, vandalism resistance, low density and good processability have made silicone rubbers based on polydimethylsiloxane (PDMS) very attractive materials in housings for outdoor insulation. Their ability to recover Hydrophobicity after oxida. tion or contamination is of paramount importance and this is the topic of this review. A critical evaluation of the chemical and physical mechanisms responsible for Hydrophobicity loss and recovery is presented.
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Hydrophobicity recovery of polydimethylsiloxane after exposure to corona discharges
Polymer, 1998Co-Authors: Henrik Hillborg, Ulf W GeddeAbstract:Abstract A high-temperature-vulcanized polydimethylsiloxane (PDMS) elastomer has been subjected to corona discharges for different periods of time in dry air. The loss and recovery of Hydrophobicity of the surface have been characterized by contact angle measurements. Immediately after exposure to corona discharges, samples showed a low surface Hydrophobicity and, on storage in dry air, a continuous increase in Hydrophobicity finally approaching the Hydrophobicity of the unexposed material. The activation energy of the Hydrophobicity recovery was two to four times greater than the activation energy of the diffusivity of low molar mass PDMS in PDMS elastomers, indicating that the diffusivity properties of the oxidized surface layer were different from that of the bulk. PDMS elastomers quenched in liquid nitrogen or subjected to small mechanical deformation (
Henrik Hillborg - One of the best experts on this subject based on the ideXlab platform.
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Silicone rubber with improved Hydrophobicity
Electrical Insulation and Dielectric Phenomena (CEIDP), 2015 IEEE Conference on, 2015Co-Authors: Hongjie Sun, Jiansheng Chen, Y. J. Wang, Henrik HillborgAbstract:In outdoor insulation, a hydrophobic surface is crucial for minimizing leakage currents during severe weather conditions and in polluted environments. Silicone rubber is a commonly used insulation material with good Hydrophobicity. However, the Hydrophobicity may be temporarily reduced or even lost when silicone rubber worked under extreme pollution events, but will gradually recover with time. The current work is aiming at developing a silicone rubber formulation with improved Hydrophobicity, such as increased hydrophobic recovery rate. This was achieved by adding silicone-based additives. The loss and recovery of Hydrophobicity of the materials after exposure to corona discharges, as well as the hydrophobic transfer ability, were assessed by contact angle measurements. In addition, an inclined plane tracking test was carried out according to IEC 60587. The modified silicone rubber exhibited a more durable Hydrophobicity during corona treatment and a faster recovery after end of exposure. The resistance to tracking and erosion behavior was maintained, compared to the reference materials. Unexpectedly, no improvement on the Hydrophobicity transfer performance was noted.
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Hydrophobicity changes in silicone rubbers
IEEE Transactions on Dielectrics and Electrical Insulation, 1999Co-Authors: Henrik Hillborg, Ulf W GeddeAbstract:Water repellency, high surface resistivity, vandalism resistance, low density and good processability have made silicone rubbers based on polydimethylsiloxane (PDMS) very attractive materials in housings for outdoor insulation. Their ability to recover Hydrophobicity after oxida. tion or contamination is of paramount importance and this is the topic of this review. A critical evaluation of the chemical and physical mechanisms responsible for Hydrophobicity loss and recovery is presented.
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Hydrophobicity recovery of polydimethylsiloxane after exposure to corona discharges
Polymer, 1998Co-Authors: Henrik Hillborg, Ulf W GeddeAbstract:Abstract A high-temperature-vulcanized polydimethylsiloxane (PDMS) elastomer has been subjected to corona discharges for different periods of time in dry air. The loss and recovery of Hydrophobicity of the surface have been characterized by contact angle measurements. Immediately after exposure to corona discharges, samples showed a low surface Hydrophobicity and, on storage in dry air, a continuous increase in Hydrophobicity finally approaching the Hydrophobicity of the unexposed material. The activation energy of the Hydrophobicity recovery was two to four times greater than the activation energy of the diffusivity of low molar mass PDMS in PDMS elastomers, indicating that the diffusivity properties of the oxidized surface layer were different from that of the bulk. PDMS elastomers quenched in liquid nitrogen or subjected to small mechanical deformation (
Wim J. Quax - One of the best experts on this subject based on the ideXlab platform.
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Signal peptide Hydrophobicity is critical for early stages in protein export by Bacillus subtilis.
FEBS Journal, 2005Co-Authors: Geeske Zanen, Bauke Oudega, Joen Luirink, Edith N. G. Houben, Rob Meima, Harold Tjalsma, Jan D.h. Jongbloed, Helga Westers, Jan Maarten Van Dijl, Wim J. QuaxAbstract:Signal peptides that direct protein export in Bacillus subtilis are overall more hydrophobic than signal peptides in Escherichia coli. To study the importance of signal peptide Hydrophobicity for protein export in both organisms, the alpha-amylase AmyQ was provided with leucine-rich (high Hydrophobicity) or alanine-rich (low Hydrophobicity) signal peptides. AmyQ export was most efficiently directed by the authentic signal peptide, both in E. coli and B. subtilis. The leucine-rich signal peptide directed AmyQ export less efficiently in both organisms, as judged from pulse-chase labelling experiments. Remarkably, the alanine-rich signal peptide was functional in protein translocation only in E. coli. Cross-linking of in vitro synthesized ribosome nascent chain complexes (RNCs) to cytoplasmic proteins showed that signal peptide Hydrophobicity is a critical determinant for signal peptide binding to the Ffh component of the signal recognition particle (SRP) or to trigger factor, not only in E. coli, but also in B. subtilis. The results show that B. subtilis SRP can discriminate between signal peptides with relatively high hydrophobicities. Interestingly, the B. subtilis protein export machinery seems to be poorly adapted to handle alanine-rich signal peptides with a low Hydrophobicity. Thus, signal peptide Hydrophobicity appears to be more critical for the efficiency of early stages in protein export in B. subtilis than in E. coli.
Haiying Tang - One of the best experts on this subject based on the ideXlab platform.
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influence of silicone surface roughness and Hydrophobicity on adhesion and colonization of staphylococcus epidermidis
Journal of Biomedical Materials Research Part A, 2009Co-Authors: Haiying Tang, Xuemei Liang, Anfeng Wang, Steven O Salley, James P Mcallister, K Simon Y NgAbstract:Bacterial adhesion and colonization are complicated processes that depend on many factors, including surface chemistry, Hydrophobicity, and surface roughness. The contribution of each of these factors has not been fully elucidated because most previous studies used different polymeric surfaces to achieve differences in properties. The objective of this study was to modify Hydrophobicity and roughness on one polymeric surface, eliminating the confounding contribution of surface chemistry. Mechanically assembled monolayer (MAM) preparation methods (both one- and two-dimensional) were used to impart different degrees of Hydrophobicity on fluoroalkylsilane (FAS)-coated silicone. Surface roughness was varied by casting the silicone to templates prepared with different abrasives. Surface Hydrophobicity was determined by contact angle measurement, whereas surface roughness was determined by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Bacterial adhesion and colonization were analyzed using a direct colony-counting method and SEM images. Hydrophobicity increased as a function of stretched length or width (Δx or Δy); it reached a maximum at Δx = 60% with one-dimensional MAM and decreased as Δx further increased to 80 and 100%. The same trend was observed for the two-dimensional MAM. After 12-h incubation, all the FAS/silicone surfaces had significantly reduced adherence of Staphylococcus epidermidis by 42–89%, compared to untreated silicone, and the degree of which is inversely related to surface Hydrophobicity. On the other hand, surface roughness had a significant effect on bacterial adhesion and colonization only when the root-mean-square roughness was higher than 200 nm. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res 2009
