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Miao W.,Lingnan Normal University | Qin L.,CAS Beijing National Laboratory for Molecular | Yang D.,CAS Beijing National Laboratory for Molecular | Jin X.,CAS Beijing National Laboratory for Molecular | Liu M.,CAS Beijing National Laboratory for Molecular
Chemistry - A European Journal | Year: 2015

A new class of L-glutamic gelators, LG12(CH2)nCOOH, containing different lengths of methylene spacer were synthesized. It was found that the gelation ability of these compounds themselves was very weak. However, when another compound, p-xylylenediamine (XEA), was introduced, the gelation ability was improved greatly. In particular, LG12(CH2)10COOH showed super-gelation ability in the presence of XEA, which could immobilize almost all of the solvents except methanol. Moreover, the formed supramolecular gels even could be molded. Interestingly, some supramolecular gels of LG12(CH2)nCOOH and XEA could respond to multiple stimuli, such as heating, shaking, sonication, and acid/base. The studies of CD spectra suggested that the supramolecular chirality induced by self-assembled chiral gelator molecules in gels could be tuned by the length of methylene spacer. In addition, the supramolecular chirality could be regulated as on/off by heating-cooling or external NH3/HCl. This would facilitate the development of dual chiroptical switches by temperature and acid/base. © 2015 Wiley-VCH Verlag GmbH & Co. KGaA. Source

Miao W.,Lingnan Normal University | Yang D.,CAS Beijing National Laboratory for Molecular | Liu M.,CAS Beijing National Laboratory for Molecular
Chemistry - A European Journal | Year: 2015

Abstract A new class of homologous gelators, LG12-(CH2)n-BSA, composed of bipyridinyl groups, L-glutamic moieties having double dodecyl chains, and linked alkyl spacers with different lengths were synthesized. It was found that these gelators could immobilize medium-polarity solvents readily and the behaviors of these gels showed a dependence on the spacer length. Of all the gels, the LG12-(CH2)11-BSA gels exhibited self-healing property and multiple-stimulus responsibility, such as heating, shaking, and sonication. The investigation of CD spectra indicated that the supramolecular chirality, which was attributed to the chiral transfer from the chiral center to the assemblies, was also closely related to the length of methylene spacers. The longer the alkyl spacers, the weaker the transmitted supramolecular chirality. Only LG12-(CH2)1-BSA gelators, which had the shortest spacers, formed right-handed nanoscale chiral twists owing to crowded hydrogen bonding interactions. Moreover, the high-polarity solvent DMF was found to be able to regulate the chiral twist as well as its pitch length readily. A new twist on healing: Self-healing supramolecular gels that are responsive to multiple stimuli were developed. The formation of nanoscale twists could be controlled by the length of the methylene spacers of the gelator molecules. The pitch of these twists could be regulated by DMF. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Wang Y.,Lingnan Normal University
Journal of Physical Organic Chemistry | Year: 2016

The reaction of N,N-dimethylaniline with tetrachloromethane in ionic liquid was found to give 4,4′-methylene-bis (N,N-dimethylaniline) in considerable yield. The ionic liquid was prepared from N,N-dimethylaniline which is also the one of raw materials for the preparation of 4,4′-methylene-bis (N,N-dimethylaniline), and acts as both solvent and catalyst in the reaction. Mild reaction conditions, enhanced rates, improved yields, and reagents' reactivity which is different from that in conventional organic solvents are the remarkable features observed in ionic liquids. In addition, the results of calculations are in good accordance with the experimental outcomes. © 2016 John Wiley & Sons, Ltd. Source

An X.,China Institute of Water Resources and Hydropower Research | Yang J.,Lingnan Normal University
Transactions of the Institute of Measurement and Control | Year: 2016

A denoising method for a hydropower unit vibration signal based on variational mode decomposition (VMD) and approximate entropy is proposed. The signal was decomposed by VMD into discrete numbers of modes, then the approximate entropy of each mode was computed. These modes were reconstructed according to a preset threshold of the approximate entropy. Finally, the denoising of the hydropower unit vibration signal can be achieved. A simulation signal and real signals of hydropower unit vibration were used to verify the proposed method. The results showed that the proposed method had a good denoising performance and was better than the wavelet transform method in the signal-to-noise ratio (SNR), root mean square error (RMSE) and partial correlation index. It was ideally suited for the online denoising of the hydropower unit vibration signal. © SAGE Publications. Source

Mo J.-X.,Lingnan Normal University
Modern Physics Letters A | Year: 2015

The thermodynamic geometry of black holes with conformal anomaly has been investigated in this paper. We study two classical kinds of thermodynamic geometry. Namely, Weinhold geometry and Ruppeiner geometry. It is shown that the condition when Weinhold scalar curvature diverges is the same as the phase transition condition characterized by the divergence of specific heat. It is also shown that Ruppeiner scalar curvature not only reveals the phase structure but also contains the information of Hawking temperature. In a word, both Weinhold metric and Ruppeiner metric can correctly reproduce the phase structure of black holes even when conformal anomaly is taken into consideration. © 2015 World Scientific Publishing Company. Source

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