Antibiotics and antibiotic resistance genes in global lakes:A review and meta-analysis

Lakes are an important source of freshwater, containing nearly 90% of the liquid surface fresh water worldwide. Long retention times in lakes mean pollutants from discharges slowly circulate around the lakes and may lead to high ecological risk for ecosystem and human health. In recent decades, antibiotics and antibiotic resistance genes (ARGs) have been regarded as emerging pollutants. The occurrence and distribution of antibiotics and ARGs in global freshwater lakes are summarized to show the pollution level of antibiotics and ARGs and to identify some of the potential risks to ecosystem and human health. Fifty-seven antibiotics were reported at least once in the studied lakes. Our meta-analysis shows that sulfamethoxazole, sulfamerazine, sulfameter, tetracycline, oxytetracycline, erythromycin, and roxithromycin were found at high concentrations in both lake water and lake sediment. There is no significant difference in the concentration of sulfonamides in lake water from China and that from other countries worldwide; however, there was a significant difference in quinolones. Erythromycin had the lowest predicted hazardous concentration for 5% of the species (HC5) and the highest ecological risk in lakes. There was no significant difference in the concentration of sulfonamide resistance genes (sul1 and sul2) in lake water and river water. There is surprisingly limited research on the role of aquatic biota in propagation of ARGs in freshwater lakes. As an environment that is susceptible to cumulative build-up of pollutants, lakes provide an important environment to study the fate of antibiotics and transport of ARGs with a broad range of niches including bacterial community, aquatic plants and animals

Exploring the Influence of Smart Product Service Systems on Enterprise Competitive Advantage from the Perspective of Value Creation

With the continuous development of information and communication technology, the development of smart product service systems (smart PSS) has become a crucial approach for enterprises to establish a competitive advantage. However, there is still a lack of clarity regarding the impact process of smart PSS on competitive advantage. This paper aims to explore the impact mechanism of smart PSS on competitive advantage from the perspective of value creation, using an intelligent connected vehicle supplier as a case study. The findings reveal that the composition of smart PSS, including smart technology, smart products, and smart services, influences competitive advantage through the value creation process, which involves relationship construction, relationship operation, and value release. Under the smart PSS environment, changes occur in subject relationships, resources, and key elements. In the context of smart PSS, deep cooperation between enterprises and partners focuses on ecological advantages, while general cooperation emphasizes benefit advantages. This research provides valuable insights into the impact of smart PSS composition on competitive advantage and offers reference values for organizations to establish competitive advantage objectives

Preparation of functionalized kaolinite/epoxy resin nanocomposites with enhanced thermal properties

In this study, kaolinite/epoxy resin nanocomposites were fabricated using functionalized kaolinite (KGS) as filler. The KGS was prepared by silylation of 3-aminopropyltriethoxysilane onto the surface of mechanically ground kaolinite. The addition of KGS into epoxy resin matrix improved the storage modulus and glass-transition temperature, compared to those of epoxy resin nanocomposites filled with raw kaolinite. Furthermore, with the increase of KGS loading, the coefficient of thermal expansion decreased gradually, and the dielectric constant slightly increased when compared to that of pure epoxy resin. The presence of kaolinite led to an improvement in the water resistance property of kaolinite/epoxy resin nanocomposites. This research provided guidance to construct high-performance kaolinite/epoxy resin nanocomposites

Effect of functionalized kaolinite on the curing kinetics of cycloaliphatic epoxy/anhydride system

Silane grafted kaolinite (KGS) was prepared through grinding kaolinite and then grafting with 3-aminopropyltriethoxysilane. The influence of KGS on the curing kinetics of cycloaliphatic epoxy resin was studied by non-isothermal differential scanning calorimetry at different heating rates. The reaction activation energy (Ea) was determined based on the Flynn–Wall–Ozawa method. The results of dynamic differential scanning calorimetry (DSC) kinetic analysis show that the surface hydroxyl groups of clay decreases the Ea from 70.6 kJ mol− 1 to 62.8 kJ mol− 1 and accelerates the curing reaction of the epoxy resin. The silane grafting reactions consume the surface hydroxyl groups of kaolinite and lead to a decrease in the catalytic efficiency of KGS in the curing of epoxy resin

Silylation of mechanically ground kaolinite

Silylated kaolinites were synthesized at 80°C without the use of inert gas protection. The method presented started with mechanical grinding of kaolinite, followed by grafting with 3-aminopropyltriethoxysilane (APTES). The mechanical grinding treatment destroyed the ordered sheets of kaolinite, formed fine fragments and generated broken bonds (undercoordinated metal ions). These broken bonds served as new sites for the condensation with APTES. Fourier transform infrared spectroscopy (FTIR) confirmed the existence of –CH2 from APTES. 29Si cross-polarization magic-angle spinning nuclear magnetic resonance spectroscopy (29Si CP/MAS NMR) showed that the principal bonding mechanism between APTES and kaolinite fitted a tridentate silylation model (T3) with a chemical shift at 66.7 ppm. The silane loadings of the silylated samples were estimated from the mass loss obtained by TG-DTG curves. The results showed that the 6-hour ground kaolinite could be grafted with the most APTES (7.0%) using cyclohexane as solvent. The loaded amount of APTES in the silylated samples obtained in different solvents decreased in the order as: nonpolar solvent > polar solvent with low dielectric constant (toluene) > polar solvent with high dielectric constant (ethanol)