The pitting corrosion behaviors of 7A60 aluminum alloy in the retrogression and re-aging （RRA） temper were investigated by electrochemical impedance spectroscopy （EIS） and electrochemical noise （EN） techniques, ...The pitting corrosion behaviors of 7A60 aluminum alloy in the retrogression and re-aging （RRA） temper were investigated by electrochemical impedance spectroscopy （EIS） and electrochemical noise （EN） techniques, and the microstructure and the second phase content of the alloy were observed and determined by scanning electron microscopy （SEM） and energy dispersive spectrometer （EDS）. The results show that there exist two different corrosion stages for 7A60 alloy in 3.5%NaCl solution, and the corrosion process can be detected by the appearance of EIS spectrum with two capacitive time constants and the wavelet fractal dimension D extracted from EN. SEM and EDS results also demonstrate that severe pitting corrosion in 7A60 alloy is mainly caused by electrochemical active MgZn2 particles, secondly by Al2MgCu and Mg2Si. Al7Cu2Fe particles make little contribution to the pitting corrosion of 7A60 alloy.展开更多
Aim To investigate the chemical constituents from Potentilla multifida L..Methods Chromatographic technique was employed for the isolation and purification of theconstituents, and the structures were identified by spe...Aim To investigate the chemical constituents from Potentilla multifida L..Methods Chromatographic technique was employed for the isolation and purification of theconstituents, and the structures were identified by spectral evidence. Results Four compounds wereisolated involving ade-nosine (1), apigenin-6-C-arabinopyranosyl-8-C-glucopyranoside (2),apigenin-7-O-β-D-glucuronide (3) and luteolin-7-O-β-D-glucuronide (4). Conclusion The fourcompounds were obtained from the genus Potentilla for the first time.展开更多
A new eremophilane sesquiterpenoid, along with two known ones, was isolated from the ethyl acetate soluble fraction of the aerial part of Coleus xanthanthus C. Y. Wu et Y. C. Huang. Their structures were elucidate...A new eremophilane sesquiterpenoid, along with two known ones, was isolated from the ethyl acetate soluble fraction of the aerial part of Coleus xanthanthus C. Y. Wu et Y. C. Huang. Their structures were elucidated as 4,5,11_trimethyl_8,9_seco_1(10),7(11)_eremophiladien_8,12_olid_9_oic acid (1), 2,9_dioxoeuryopsin (2) and 9_oxoeuryopsin (3) by spectral methods. The 1H_NMR and 13 C NMR data of compounds 1, 2 and 3 were unambiguously assigned on the basis of two_dimensional NMR spectroscopy.展开更多
The ethoxycarbonyl isothiocyanate has been investigated by using supersonic jet Fourier transform microwave spectroscopy.Two sets of rotational spectra belonging to conformers TCC(with the backbone of C-C-O-C,C-O-C=O,...The ethoxycarbonyl isothiocyanate has been investigated by using supersonic jet Fourier transform microwave spectroscopy.Two sets of rotational spectra belonging to conformers TCC(with the backbone of C-C-O-C,C-O-C=O,and O-C(=O)-NCS being trans,cis,and cis arranged,respectively)and GCC(gauche,cis,and cis arrangement of the C-C-O-C,C-O-C=O,and O-C(=O)-NCS)have been measured and assigned.The measurements of13C,15N and34S mono-substituted species of the two conformers have also been performed.The comprehensive rotational spectroscopic investigations provide accurate values of rotational constants and14N quadrupole coupling constants,which lead to structural determinations of the two conformers of ethoxycarbonyl isothiocyanate.For conformer TCC,the values of Pcckeep constant upon isotopic substitution,indicating that the heavy atoms of TCC are effectively located in the ab plane.展开更多
基金Project(13JCZDJC29500)supported by the Key Project of Tianjin Natural Science Foundation,ChinaProjects(2011CB610505,2014CB046801)supported by the National Basic Research Program of ChinaProject(20120032110029)supported by the Specialized Research Fund for the Doctoral Program of Higher Education,China
文摘The pitting corrosion behaviors of 7A60 aluminum alloy in the retrogression and re-aging （RRA） temper were investigated by electrochemical impedance spectroscopy （EIS） and electrochemical noise （EN） techniques, and the microstructure and the second phase content of the alloy were observed and determined by scanning electron microscopy （SEM） and energy dispersive spectrometer （EDS）. The results show that there exist two different corrosion stages for 7A60 alloy in 3.5%NaCl solution, and the corrosion process can be detected by the appearance of EIS spectrum with two capacitive time constants and the wavelet fractal dimension D extracted from EN. SEM and EDS results also demonstrate that severe pitting corrosion in 7A60 alloy is mainly caused by electrochemical active MgZn2 particles, secondly by Al2MgCu and Mg2Si. Al7Cu2Fe particles make little contribution to the pitting corrosion of 7A60 alloy.
文摘Aim To investigate the chemical constituents from Potentilla multifida L..Methods Chromatographic technique was employed for the isolation and purification of theconstituents, and the structures were identified by spectral evidence. Results Four compounds wereisolated involving ade-nosine (1), apigenin-6-C-arabinopyranosyl-8-C-glucopyranoside (2),apigenin-7-O-β-D-glucuronide (3) and luteolin-7-O-β-D-glucuronide (4). Conclusion The fourcompounds were obtained from the genus Potentilla for the first time.
文摘A new eremophilane sesquiterpenoid, along with two known ones, was isolated from the ethyl acetate soluble fraction of the aerial part of Coleus xanthanthus C. Y. Wu et Y. C. Huang. Their structures were elucidated as 4,5,11_trimethyl_8,9_seco_1(10),7(11)_eremophiladien_8,12_olid_9_oic acid (1), 2,9_dioxoeuryopsin (2) and 9_oxoeuryopsin (3) by spectral methods. The 1H_NMR and 13 C NMR data of compounds 1, 2 and 3 were unambiguously assigned on the basis of two_dimensional NMR spectroscopy.
基金The support from the National Natural Science Foundation of China(No.22273009)Chongqing University。
文摘The ethoxycarbonyl isothiocyanate has been investigated by using supersonic jet Fourier transform microwave spectroscopy.Two sets of rotational spectra belonging to conformers TCC(with the backbone of C-C-O-C,C-O-C=O,and O-C(=O)-NCS being trans,cis,and cis arranged,respectively)and GCC(gauche,cis,and cis arrangement of the C-C-O-C,C-O-C=O,and O-C(=O)-NCS)have been measured and assigned.The measurements of13C,15N and34S mono-substituted species of the two conformers have also been performed.The comprehensive rotational spectroscopic investigations provide accurate values of rotational constants and14N quadrupole coupling constants,which lead to structural determinations of the two conformers of ethoxycarbonyl isothiocyanate.For conformer TCC,the values of Pcckeep constant upon isotopic substitution,indicating that the heavy atoms of TCC are effectively located in the ab plane.
