The present study deals with the study of some Friedel-Crafts alkylating system and the accurate measurement of hyperfine coupling constants by ESR and ENDOR techniques. The results indicate that the observed ESR spec...The present study deals with the study of some Friedel-Crafts alkylating system and the accurate measurement of hyperfine coupling constants by ESR and ENDOR techniques. The results indicate that the observed ESR spectra are due to polycyclic aromatic radical cations formed from their parent hydrocarbons.It is suggested that benzyl halides produced in the Friedel-Crafts alkylating reaction undergo Scholl condensation reaction to give polycyclic aromatic hydrocarbons, which were converted into the corresponding polycyclic aromatic radical cations in the presence of aluminum chloride.展开更多
The ENDOR spectrum of ^(14)N-^(63)Cu-HAP complex in DMSO/EtOH (5:1) freezing solution at 20 K has been studied using orientational selective method in this paper. The anisotropic superhyperfine coupling tensor and qus...The ENDOR spectrum of ^(14)N-^(63)Cu-HAP complex in DMSO/EtOH (5:1) freezing solution at 20 K has been studied using orientational selective method in this paper. The anisotropic superhyperfine coupling tensor and qusdrupole coupling tensor of ligand ^(14)N nucleus, and the superhyperfine coupling tensor of various ~1H nuclei have been measured precisely. Comparing the superhyperfine coupling tensor of ^(14)N-nucleus with previous work shows that the analytical method of spectrum is reasonable and the data are reliable in our previous work.展开更多
Although colonoscopy has been proven effective in reducing the incidence of colorectal cancer through the detection and removal of precancerous lesions, it remains an imperfect examination, as it can fail in detecting...Although colonoscopy has been proven effective in reducing the incidence of colorectal cancer through the detection and removal of precancerous lesions, it remains an imperfect examination, as it can fail in detecting up to almost one fourth of existing adenomas. Among reasons accounting for such failures, is the inability to meticulously visualize the colonic mucosa located either proximal to haustral folds or anatomic curves, including the hepatic and splenic flexures. In order to overcome these limitations, various colonoscope attachments aiming to improve mucosal visualization have been developed. All of them-transparent cap, Endocuff, Endocuff Vision and Endorings-are simply mounted onto the distal tip of the scope. In this review article, we introduce the rationale of their development, present their mode of action and discuss in detail the effect of their implementation in the detection of lesions during colonoscopy.展开更多
Multifrequency,multitechnique pulse EPR spectroscopy was employed to unravel the spin Hamiltonian parameters of^(17)O in the[Fe^(Ⅴ)=O]moiety with two different tetraamido macrocyclic ligands(TAMLs),[Fe^(Ⅴ)(O)(TAML-1...Multifrequency,multitechnique pulse EPR spectroscopy was employed to unravel the spin Hamiltonian parameters of^(17)O in the[Fe^(Ⅴ)=O]moiety with two different tetraamido macrocyclic ligands(TAMLs),[Fe^(Ⅴ)(O)(TAML-1)]^(−)(1,H_(4)(TAML-1)=3,4,8,9-tetrahydro-3,3,6,6,9-hexamethyl-1H-1,4,8,11-benzotetraazocyclotridecane-2,5,7,10-(6H,11H)-tetrone)and[Fe^(Ⅴ)(O)(TAML-2)]^(−)(2,H_(4)(TAML-2)=H_(4)[(Me_(2)CNCOCMe_(2)NCO)_(2)CMe_(2)]),to investigate the electronic structure of Fe^(Ⅴ)-oxo species.Although rigorous computational studies on highvalent iron-oxo species have been reported recently,experimental evidence to explicate the electronic structure of Fe^(Ⅴ)-oxo species is sparse.In particular,a complete hyperfine tensor of^(17)O can hardly be detected.Herein,we successfully probed the hyperfine tensor of^(17)O of the Fe^(Ⅴ)-oxo moiety using ENDOR spectroscopy.Hence,the EPR spectroscopic results reported here provide a conclusive experimental basis for elucidating the electronic structure of the Fe^(Ⅴ)-oxo complex.Moreover,the reactivity of the two different complexes is very distinct,and our results may provide insight into how their electronic structure contributes to their reactivity.展开更多
基金Study supported by the Science and Technique Foundation of Lanzhou Branch, Academia Sinica.
文摘The present study deals with the study of some Friedel-Crafts alkylating system and the accurate measurement of hyperfine coupling constants by ESR and ENDOR techniques. The results indicate that the observed ESR spectra are due to polycyclic aromatic radical cations formed from their parent hydrocarbons.It is suggested that benzyl halides produced in the Friedel-Crafts alkylating reaction undergo Scholl condensation reaction to give polycyclic aromatic hydrocarbons, which were converted into the corresponding polycyclic aromatic radical cations in the presence of aluminum chloride.
文摘The ENDOR spectrum of ^(14)N-^(63)Cu-HAP complex in DMSO/EtOH (5:1) freezing solution at 20 K has been studied using orientational selective method in this paper. The anisotropic superhyperfine coupling tensor and qusdrupole coupling tensor of ligand ^(14)N nucleus, and the superhyperfine coupling tensor of various ~1H nuclei have been measured precisely. Comparing the superhyperfine coupling tensor of ^(14)N-nucleus with previous work shows that the analytical method of spectrum is reasonable and the data are reliable in our previous work.
文摘Although colonoscopy has been proven effective in reducing the incidence of colorectal cancer through the detection and removal of precancerous lesions, it remains an imperfect examination, as it can fail in detecting up to almost one fourth of existing adenomas. Among reasons accounting for such failures, is the inability to meticulously visualize the colonic mucosa located either proximal to haustral folds or anatomic curves, including the hepatic and splenic flexures. In order to overcome these limitations, various colonoscope attachments aiming to improve mucosal visualization have been developed. All of them-transparent cap, Endocuff, Endocuff Vision and Endorings-are simply mounted onto the distal tip of the scope. In this review article, we introduce the rationale of their development, present their mode of action and discuss in detail the effect of their implementation in the detection of lesions during colonoscopy.
基金supported by the National Research Foundation of Korea(NRF-2017M3D1A1039380 and NRF-2020R1F1A1069151)KBSI grant C1300000 to S.H.K+1 种基金supported by the NRF of Korea through CRI(NRF-2012R1A3A2048842 to W.N.)the Basic Science Research Program(NRF-2020R1I1A1A01074630 to Y.-M.L.).
文摘Multifrequency,multitechnique pulse EPR spectroscopy was employed to unravel the spin Hamiltonian parameters of^(17)O in the[Fe^(Ⅴ)=O]moiety with two different tetraamido macrocyclic ligands(TAMLs),[Fe^(Ⅴ)(O)(TAML-1)]^(−)(1,H_(4)(TAML-1)=3,4,8,9-tetrahydro-3,3,6,6,9-hexamethyl-1H-1,4,8,11-benzotetraazocyclotridecane-2,5,7,10-(6H,11H)-tetrone)and[Fe^(Ⅴ)(O)(TAML-2)]^(−)(2,H_(4)(TAML-2)=H_(4)[(Me_(2)CNCOCMe_(2)NCO)_(2)CMe_(2)]),to investigate the electronic structure of Fe^(Ⅴ)-oxo species.Although rigorous computational studies on highvalent iron-oxo species have been reported recently,experimental evidence to explicate the electronic structure of Fe^(Ⅴ)-oxo species is sparse.In particular,a complete hyperfine tensor of^(17)O can hardly be detected.Herein,we successfully probed the hyperfine tensor of^(17)O of the Fe^(Ⅴ)-oxo moiety using ENDOR spectroscopy.Hence,the EPR spectroscopic results reported here provide a conclusive experimental basis for elucidating the electronic structure of the Fe^(Ⅴ)-oxo complex.Moreover,the reactivity of the two different complexes is very distinct,and our results may provide insight into how their electronic structure contributes to their reactivity.
