A novel metal organic compound of Zn2+ coordinated with 4,5-diazafluorene- 9-one-N2 (C22H12N6) has been synthesized under solvothermal condition. Single-crystal X-ray diffraction analysis showed that the compound is a...A novel metal organic compound of Zn2+ coordinated with 4,5-diazafluorene- 9-one-N2 (C22H12N6) has been synthesized under solvothermal condition. Single-crystal X-ray diffraction analysis showed that the compound is a one-dimensional zig-zag chain structure combined by Cl…H–C bonds. The crystal is of orthorhombic, space group Pnna, C22H12N6Cl2Zn, Mr = 496.65, a = 8.1132(13), b = 18.983(3), c = 13.116(2) ?, Z = 4, V = 2020.2(5) ?3, Dc = 1.633 g/cm3, μ = 1.504 mm-1, F(000) = 1000, T = 293(2) K, the final R = 0.0626 and wR = 0.1474 for 2390 unique reflections and 150 parameters with I > 2σ(I). The refinement method was full-matrix least-squares on F2 with GOF = 0.951. This compound was also characterized by FT-IR, Raman, UV-vis spectra, and TG-DTA.展开更多
A new series of liquid crystal polyesters with T-shaped two-dimensional mesogenic units weresynthesized by melt polycondensation of the diacetates of 2-(4'-alkoxy -phenyl)-hydroquinones with 4,4'-alkylenedioxy...A new series of liquid crystal polyesters with T-shaped two-dimensional mesogenic units weresynthesized by melt polycondensation of the diacetates of 2-(4'-alkoxy -phenyl)-hydroquinones with 4,4'-alkylenedioxydibenzoic acid. The polymers were characterized by using polarized microscopy, DSC and X-ray diffraction. It was realized that all the polymers have nematic thermotropic liquid crystallinecharacteristics. The melting temperature (T_m) and isotropization temperature (T_i) of the polymers changeregularly with varying lengths of the alkoxy side group and the length of the alkylene group in the main chainin company with an even-odd effect. The mesophase temperature range also varies regularly with the polymerstructure. It is shown that the mesophase range has been widened.展开更多
Despite recent advances in mine health and safety, roof collapse and instabilities are still the leading causes of injury and fatality in underground mining operations. Improving safety and optimum design of ground su...Despite recent advances in mine health and safety, roof collapse and instabilities are still the leading causes of injury and fatality in underground mining operations. Improving safety and optimum design of ground support requires good and reliable ground characterization. While many geophysical methods have been developed for ground characterizations, their accuracy is insufficient for customized ground support design of underground workings. The actual measurements on the samples of the roof and wall strata from the exploration boring are reliable but the related holes are far apart, thus unsuitable for design purposes. The best source of information could be the geological back mapping of the roof and walls, but this is disruptive to mining operations, and provided information is only from rock surface.Interpretation of the data obtained from roof bolt drilling can offer a good and reliable source of information that can be used for ground characterization and ground support design and evaluations. This paper offers a brief review of the mine roof characterization methods, followed by introduction and discussion of the roof characterization methods by instrumented roof bolters. A brief overview of the results of the preliminary study and initial testing on an instrumented drill and summary of the suggested improvements are also discussed.展开更多
心血管磁共振(cardiovascular magnetic resonance, CMR)具有无创、无辐射、多参数成像的优势,能够实现对心脏形态、功能和组织学信息的“一站式”评估,在心血管疾病的精准医疗中发挥着无可替代的重要作用。2023年CMR研究取得了长足的进...心血管磁共振(cardiovascular magnetic resonance, CMR)具有无创、无辐射、多参数成像的优势,能够实现对心脏形态、功能和组织学信息的“一站式”评估,在心血管疾病的精准医疗中发挥着无可替代的重要作用。2023年CMR研究取得了长足的进展:组织特征成像、心肌应变分析等技术不断推陈出新,探索更多临床适应证,并逐步完成标准化应用转化;非缺血性心脏病、缺血性心脏病等领域的CMR应用在新版指南中备受重视,且优质循证证据不断涌现,鼓励其更多地参与到心血管临床管理之中。本文将从技术和临床应用两方面系统性回顾其中代表性成果,以期为现阶段医疗实践提供实时有效的指导。展开更多
基金This work was supported by the Natural Science Foundation (No. 20201013) and "Plan of Outstanding Talents" of the Chinese Academy of Sciences
文摘A novel metal organic compound of Zn2+ coordinated with 4,5-diazafluorene- 9-one-N2 (C22H12N6) has been synthesized under solvothermal condition. Single-crystal X-ray diffraction analysis showed that the compound is a one-dimensional zig-zag chain structure combined by Cl…H–C bonds. The crystal is of orthorhombic, space group Pnna, C22H12N6Cl2Zn, Mr = 496.65, a = 8.1132(13), b = 18.983(3), c = 13.116(2) ?, Z = 4, V = 2020.2(5) ?3, Dc = 1.633 g/cm3, μ = 1.504 mm-1, F(000) = 1000, T = 293(2) K, the final R = 0.0626 and wR = 0.1474 for 2390 unique reflections and 150 parameters with I > 2σ(I). The refinement method was full-matrix least-squares on F2 with GOF = 0.951. This compound was also characterized by FT-IR, Raman, UV-vis spectra, and TG-DTA.
基金This work was supported by the National Natural Science Foundation of China.
文摘A new series of liquid crystal polyesters with T-shaped two-dimensional mesogenic units weresynthesized by melt polycondensation of the diacetates of 2-(4'-alkoxy -phenyl)-hydroquinones with 4,4'-alkylenedioxydibenzoic acid. The polymers were characterized by using polarized microscopy, DSC and X-ray diffraction. It was realized that all the polymers have nematic thermotropic liquid crystallinecharacteristics. The melting temperature (T_m) and isotropization temperature (T_i) of the polymers changeregularly with varying lengths of the alkoxy side group and the length of the alkylene group in the main chainin company with an even-odd effect. The mesophase temperature range also varies regularly with the polymerstructure. It is shown that the mesophase range has been widened.
基金supported by the funding of the National Institute for Occupational Safety and Health under a contract with the Pennsylvania State University as part of the capacity building in ground supportthe funding from TüBITAK of Turkey has been used to support the sabbatical leave of Dr.Kahraman who made some contributions to this study
文摘Despite recent advances in mine health and safety, roof collapse and instabilities are still the leading causes of injury and fatality in underground mining operations. Improving safety and optimum design of ground support requires good and reliable ground characterization. While many geophysical methods have been developed for ground characterizations, their accuracy is insufficient for customized ground support design of underground workings. The actual measurements on the samples of the roof and wall strata from the exploration boring are reliable but the related holes are far apart, thus unsuitable for design purposes. The best source of information could be the geological back mapping of the roof and walls, but this is disruptive to mining operations, and provided information is only from rock surface.Interpretation of the data obtained from roof bolt drilling can offer a good and reliable source of information that can be used for ground characterization and ground support design and evaluations. This paper offers a brief review of the mine roof characterization methods, followed by introduction and discussion of the roof characterization methods by instrumented roof bolters. A brief overview of the results of the preliminary study and initial testing on an instrumented drill and summary of the suggested improvements are also discussed.
文摘心血管磁共振(cardiovascular magnetic resonance, CMR)具有无创、无辐射、多参数成像的优势,能够实现对心脏形态、功能和组织学信息的“一站式”评估,在心血管疾病的精准医疗中发挥着无可替代的重要作用。2023年CMR研究取得了长足的进展:组织特征成像、心肌应变分析等技术不断推陈出新,探索更多临床适应证,并逐步完成标准化应用转化;非缺血性心脏病、缺血性心脏病等领域的CMR应用在新版指南中备受重视,且优质循证证据不断涌现,鼓励其更多地参与到心血管临床管理之中。本文将从技术和临床应用两方面系统性回顾其中代表性成果,以期为现阶段医疗实践提供实时有效的指导。
