Silver nanoparticles with average diameter of 10 ± 3 nm were synthesized within the sieves of poly(N-isopropylacrylamide-2-hydroxyethylmethacrylate-acrylic acid)(p(NIPAAm-HEMA-AAc))polymer microgels. Free radial emulsion polymerization was employed for synthesis of p(NIPAAm-HEMA-AAc) polymer microgels. Silver nanoparticles were introduced within the microgels sphere by in situ reduction method. Microgels and hybrid microgels were characterized by Fourier transform infrared spectroscopy, ultra violet-visible spectroscopy,transmission electron microscopy and dynamic light scattering measurements. Catalytic activity of Ag-p(NIPAAm-HEMA-AAc) hybrid microgels was studied using catalytic reduction of 4-nitrophenol(4-NP) as a model reaction in aqueous media. The influence of sodium borohydride(Na BH4) concentration, catalyst dose and 4-NP concentration on catalytic reduction of 4-NP was investigated. A linear relationship was found between catalyst dose and apparent rate constant(kapp). The mechanism of catalysis by hybrid microgels was explored for further development in this area. The deep analysis of catalytic process reveals that the unique combination of NIPAAm, HEMA and AAc does not only stabilize silver nanoparticles in polymer network but it also enhances the mass transport of hydrophilic substrate like 4-NP from outside to inside the polymer network. 相似文献
Objective: With increasing traffic volume and urban development, increasing numbers of underground tunnels have been constructed to relieve conflict between strained land and heavy traffic. However, as more long tunnels are constructed, tunnel traffic safety is becoming increasingly serious. Thus, it is necessary to acquire their implications and impacts. This study examined 4,539 traffic accidents that have occurred in 14 Shanghai river-crossing tunnels for the period 2011–2012 and analyze the correlation between potential factors and accident injury severity.
Methods: An ordered logit model was developed to examine the correlation between potential factors and accident injury severity.
Results: Results show that increased injury severity is associated with male drivers, drivers aged 65 years or older, accident time from midnight to dawn, weekends, wet road surface, goods vehicles, 3 or more vehicles, 4 or more lanes, middle speed limits (50–79 km/h), zone 3, extra-long tunnels (over 3,000 m), and maximum longitudinal gradient.
Conclusions: This article aims to provide useful information for engineers to develop interventions and countermeasures to improve tunnel safety in China. 相似文献
Assessment of the behavior and fate of engineered nanoparticles (ENPs) in natural aquatic media is crucial for the identification of environmentally critical properties of the ENPs. Here we present a methodology for testing the dispersion stability, ζ-potential and particle size of engineered nanoparticles as a function of pH and water composition. The results obtained from already widely used titanium dioxide nanoparticles (Evonik P25 and Hombikat UV-100) serve as a proof-of-concept for the proposed testing scheme. In most cases the behavior of the particles in the tested settings follows the expectations derived from classical DLVO theory for metal oxide particles with variable charge and an isoelectric point at around pH 5, but deviations also occur. Regardless of a 5-fold difference in BET specific surface area particles composed of the same core material behave in an overall comparable manner. The presented methodology can act as a basis for the development of standardised methods for comparing the behavior of different nanoparticles within aquatic systems. 相似文献
This review focuses on the occurrence and interactions of engineered nanoparticles(ENPs)and brominated flame retardants(BFRs) such as polybrominated diphenyl ethers(PBDEs)in water systems and the generation of highly complex compounds in the environment.The release of ENPs and BFRs(e.g. PBDEs) to aquatic environments during their usage and disposal are summarised together with their key interaction mechanisms. The major interaction mechanisms including electrostatic, van der Waals, hydrophobic, ... 相似文献