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71.
A closed 2-cell embedding of a graph embedded in some surface is an embedding such that each face is bounded by a cycle in the graph. The strong embedding conjecture says that every 2-connected graph has a closed 2-cell embedding in some surface. In this paper, we prove that any 2-connected graph without V8 (the Möbius 4-ladder) as a minor has a closed 2-cell embedding in some surface. As a corollary, such a graph has a cycle double cover. The proof uses a classification of internally-4-connected graphs with no V8-minor (due to Kelmans and independently Robertson), and the proof depends heavily on such a characterization. 相似文献
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Reactive copolymer functionalized graphene sheet for enhanced mechanical and thermal properties of epoxy composites 下载免费PDF全文
Qiang Ma Jing Luo Yuanxun Chen Wei Wei Ren Liu Xiaoya Liu 《Journal of polymer science. Part A, Polymer chemistry》2015,53(23):2776-2785
Uniform dispersion of graphene nanosheets (GNS) in a polymer matrix with strong filler–matrix interfacial interaction, preserving intrinsic material properties of GNS, is the critical factor for application of GNS in polymer composites. In this work, a novel reactive copolymer VCz–GMA containing carbazole and epoxide group was designed, synthesized and employed to noncovalently functionalize GNS for preparing epoxy nanocomposites with enhanced mechanical properties. The presence of carbazole groups in VCz–GMA enables the tight absorption of copolymer on to graphene surface via π–π stacking interaction, as evidenced by Raman and fluorescence spectroscopy, whereas the epoxide segments chemically reacts with the epoxy matrix, improving the compatibility and interaction of graphene with epoxy matrix. As a result, the VCz–GMA–GNS/epoxy composite showed a remarkable enhancement in both mechanical and thermal property than either the pure epoxy or the graphene/epoxy composites. The incorporation of 0.35 wt % VCz–GMA–GNS yields a tensile strength of 55.72 MPa and elongation at break of 3.45, which are 42 and 191% higher than the value of pure epoxy, respectively. Increased glass transition temperature and thermal stability of the epoxy composites were also observed. In addition, a significant enhancement in thermal conductivity was achieved with only 1 wt % VCz–GMA–GNS loading. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2776–2785 相似文献
75.
The existence of global attractors is proved for the MHD equations with damping terms and on a bounded domain . First we establish the well-posedness of strong solutions. Then, the continuity of the corresponding semigroup is verified under the assumption , which is guided by Gagliardo-Nirenberg inequality. Finally, the system is shown to possess an -global attractor and an -global attractor. 相似文献
76.
Chen Zhiyong Lin Xiaoya Liang Jie Wang Chunwei Min Junyu Wang Yaxiong Liao Sen Huang Yingheng 《Journal of Thermal Analysis and Calorimetry》2022,147(12):6817-6823
Journal of Thermal Analysis and Calorimetry - Due to their ability to form white light by mixture of blue emission and yellow emission from Dy3+ ions, Dy3+-doped phosphors have attracted much... 相似文献
77.
Biomorphic calcium phosphate (CaP) microspheres with hierarchical porous structure were synthesized using natural cole pollen grains as templates and were further employed for the immobilization of horseradish peroxidase (HRP). Scanning electron microscopy and Fourier transform infrared spectroscopy revealed (a) the porous structure of the CaP microspheres, (b) the effective immobilization, and (c) the retention of the conformation of HRP on CaP. The immobilized HRP was placed on a glassy carbon electrode where it underwent a direct, fully reversible, and surface-controlled redox reaction with an electron transfer rate constant of 1.96 s?1. It also exhibits high sensitivity to the reduction of H2O2. The response to H2O2 is linear in the 5.00 nM to 1.27 μM concentration range, and the sensitivity is 30357 μA?mM?1?cm?2. The detection limit (at an SNR of 3) is as low as 1.30 nM. The apparent Michaelis–Menten constant (K M app ) of the immobilized enzyme is 0.92 μM. This new CaP with hierarchical porous structure therefore represents a material that can significantly promote the direct electron transfer between HRP and an electrode, and is quite attractive with respect to the construction of biosensors. Figure
Biomorphic calcium phosphate microspheres with hierarchical porous has been synthesized using natural cole pollen grains as templates and were further employed for the immobilization of horseradish peroxidase to construct biosensors with high sensitivity and selectivity. 相似文献
78.
Meiling Chen Meng Sun Lixiang Wang Xiaoya Liu 《Journal of Dispersion Science and Technology》2014,35(4):494-500
Five coarse-grained models were built for amphiphilic random copolymers. The self-assembly of amphiphilic random copolymers in selective solvent was investigated via dissipative particle dynamics simulations. The simulation results showed that the content of hydrophilic particles and the repulsive parameter between solvent and copolymer particles were two key factors of the vesicle formation. We report herein on how to control the self-assembled morphology evolution. The two mechanisms of vesicle formation from amphiphilic random copolymers are found through investigating the dynamic processes of vesicle formation, which is in accordance with the experiment and simulation results of amphiphilic block copolymer reported in the literature. 相似文献
79.
Pickering Emulsion Stabilized by Self-Assembled Micelles of Amphiphilic Random Copolymer P(St-co-DM)
Meiling Chen Zhixin Geng Meng Sun Xiaoya Liu Shanshan Chen 《Journal of Dispersion Science and Technology》2014,35(6):757-764
Self-assembled polymeric micelles can be used as efficient particulate emulsifiers. Styrene (St) and dimethylaminoethyl methacrylate (DM) were used to synthesize the amphiphilic random copolymer P(St-co-DM). This copolymer self-assembles into spherical polymeric micelles. The polymeric micelles show surface activity and pH sensitivity for producing Pickering emulsion. The experiment shows that the stability of the emulsion increases with the micelle concentration. The emulsion can only be formed when the salt concentration is below a certain limiting value. Using the white oil as the oil phase, polymeric micelles have emulsification in a large pH range. The emulsifying performance of the polymeric micelles could be enhanced by raising the water/oil volume ratio. 相似文献
80.
A new method for the determination of roxithromycin based on the fluorescence quenching of 3-mercaptopropionic acid-capped CdTe quantum dots (MPA-CdTe QDs) was developed. In ethanol medium, the fluorescence of CdTe quantum dots at 552 nm was quenched in the presence of roxithromycin. Based on this a simple, sensitive, and selective method for rapid determination of roxithromycin was described. Reaction time, interfering substances on the fluorescence quenching, and mechanism of the interaction of CdTe QDs with roxithromycin were investigated. After optimization, the proposed method allows the determination of roxithromycin over the range 25.0-350.0 μg ml−1. The detection limit is 4.6 μg ml−1. The proposed method was successfully applied to commercial capsules and tablets with satisfactory results. The recovery of the method was in the range of 96.8-102.5%. 相似文献