RESUMO
Waterborne polyurethane (WPU) coatings hold advantages of good toughness, low cost and environmental protection. However, the low water contact angle (WCA), poor wear and corrosion resistance make them unsuitable for application in the superhydrophobic coatings such as antipollution flashover coatings for transmission lines, self-cleaning coatings for outdoor equipment and waterproof textiles. A series of superhydrophobic WPU composites (SHWPUCs) with micro-rough surface structure was prepared by electrostatic spraying nano-SiO2 particles on WPU composites with low surface energy. It showed that as the hydrophobic system content rose the WCAs of the composites first increased and then remained stationary; however, the adhesion and corrosion resistance first increased and then decreased. An appropriate addition of the hydrophobic system content would lead to a dense coating structure, but an excessive addition could increase the interfaces in the coating and then reduce the coating performance. When the mass ratio of the WPU dispersion, polytetrafluoroethylene (PTFE) particles and modified polydimethylsiloxane was 8:0.3:0.4, 10 g/m2 nano-SiO2 particles were sprayed on the uncured coating surface to construct the SHWPUC with a WCA of 156°. Compared with pure WPU coating, its adhesion and corrosion resistance increased by 12.5% and one order of magnitude, respectively; its wear rate decreased by 88.8%.
RESUMO
Many studies have examined the association between the MGMT Leu84Phe polymorphism gene polymorphisms and lung cancer risk in various populations, but their results have been inconsistent. To assess this relationship more precisely, a meta-analysis was performed. The PubMed and CNKI database was searched for case-control studies published up to Nov. 2013. Data were extracted and pooled odds ratios (OR) with 95% confidence intervals (CI) were calculated. Ultimately, 7 studies, comprising 3,094 lung cancer cases and 4,216 controls, were included. Overall, for (Phe/Phe+Phe/Leu) versus Leu/Leu, the pooled OR for all studies was 1.08 (95% CI = 0.97-1.21 P = 0.518 for heterogeneity); for Phe/Phe versus Leu/Leu and Phe versus Leu, the pooled OR was 1.10 (95% CI = 0.99-1.21 P = 0.445 for heterogeneity) and 1.46 (95% CI = 1.05-2.02 P = 0.352 for heterogeneity), respectively. In the stratified analysis by ethnicity, significantly risks were found among Caucasians not in Asians. This meta-analysis suggests that the MGMT Leu84Phe polymorphisms are associated with lung cancer risk among Caucasians not in Asians.
