The purpose of this study was to isolate a new compound from the seeds of Combretum quadrangulare Kurz, which showed antibacterial activity. The seeds were macerated with 95% of ethanol and then purified by column chr...The purpose of this study was to isolate a new compound from the seeds of Combretum quadrangulare Kurz, which showed antibacterial activity. The seeds were macerated with 95% of ethanol and then purified by column chromatography using Avicel as the adsorbent. After that, 50% of methanol in water was used as the eluting solvent and continued to further purify by Avicel preparative layer chromatogram 2 times using 80% of methanol in water as developing solvent. MIC of pure compound was done by two fold dilution method. Muller Hinton agar was selected as the media. The new compound was found as combretin, a steroidal alkaloid, and showed antibacterial activity against Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853 better than Staphylococcus aureus ATCC 25923.展开更多
Combretin is the steroidal alkaloid isolated from the seeds of Combretum quadrangulare Kurz. by macerated powder of the seeds with 95% ethanol. Purified further by avicel column chromatography and preparative thin lay...Combretin is the steroidal alkaloid isolated from the seeds of Combretum quadrangulare Kurz. by macerated powder of the seeds with 95% ethanol. Purified further by avicel column chromatography and preparative thin layer chromatography. Combretin was investigated for anti-mycobacterium and anti-cancer activities. Combretin was inactive against Mycobacterium tuberculosis but showed anti-cancer activities against human hepatocarcinoma （Hep G2） ATCC HB-8065 and human caucasian colon adenocarcinoma （Caco2） ATCC HTB-39 at concentration greater than 300 mcg/ml in DMSO （Dimethyl sulfoxide）.展开更多
The shear failure of intact rock under thermo-mechanical(TM)coupling conditions is common,such as in enhanced geothermal mining and deep mine construction.Under the effect of a continuous engineering disturbance,shear...The shear failure of intact rock under thermo-mechanical(TM)coupling conditions is common,such as in enhanced geothermal mining and deep mine construction.Under the effect of a continuous engineering disturbance,shear-formed fractures are prone to secondary instability,posing a severe threat to deep engineering.Although numerous studies regarding three-dimensional(3D)morphologies of fracture surfaces have been conducted,the understanding of shear-formed fractures under TM coupling conditions is limited.In this study,direct shear tests of intact granite under various TM coupling conditions were conducted,followed by 3D laser scanning tests of shear-formed fractures.Test results demonstrated that the peak shear strength of intact granite is positively correlated with the normal stress,whereas it is negatively correlated with the temperature.The internal friction angle and cohesion of intact granite significantly decrease with an increase in the temperature.The anisotropy,roughness value,and height of the asperities on the fracture surfaces are reduced as the normal stress increases,whereas their variation trends are the opposite as the temperature increases.The macroscopic failure mode of intact granite under TM coupling conditions is dominated by mixed tensileeshear and shear failures.As the normal stress increases,intragranular fractures are developed ranging from a local to a global distribution,and the macroscopic failure mode of intact granite changes from mixed tensileeshear to shear failure.Finally,3D morphological characteristics of the asperities on the shear-formed fracture surfaces were analyzed,and a quadrangular pyramid conceptual model representing these asperities was proposed and sufficiently verified.展开更多
用扩展有限元法XFEM(Extended Finite Element Method)解决夹杂问题时,夹杂与基质的界面把单元分成若干部分。求单元刚度矩阵时,需要分别在这各个部分求积分。找到便于程序编制的描述各积分区域几何形状的方法是亟待解决的问题。本文把...用扩展有限元法XFEM(Extended Finite Element Method)解决夹杂问题时,夹杂与基质的界面把单元分成若干部分。求单元刚度矩阵时,需要分别在这各个部分求积分。找到便于程序编制的描述各积分区域几何形状的方法是亟待解决的问题。本文把各积分区域的形成过程看成是圆对四边形的多次切割。考虑切剩区域与圆的关系时,把不完整的边仍看作完整的边,把切剩区域看成是四边形或是切去一两条边的四边形。采用排列组合的方法,把它们与圆的所有位置关系列了出来。展开更多
文摘The purpose of this study was to isolate a new compound from the seeds of Combretum quadrangulare Kurz, which showed antibacterial activity. The seeds were macerated with 95% of ethanol and then purified by column chromatography using Avicel as the adsorbent. After that, 50% of methanol in water was used as the eluting solvent and continued to further purify by Avicel preparative layer chromatogram 2 times using 80% of methanol in water as developing solvent. MIC of pure compound was done by two fold dilution method. Muller Hinton agar was selected as the media. The new compound was found as combretin, a steroidal alkaloid, and showed antibacterial activity against Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853 better than Staphylococcus aureus ATCC 25923.
文摘Combretin is the steroidal alkaloid isolated from the seeds of Combretum quadrangulare Kurz. by macerated powder of the seeds with 95% ethanol. Purified further by avicel column chromatography and preparative thin layer chromatography. Combretin was investigated for anti-mycobacterium and anti-cancer activities. Combretin was inactive against Mycobacterium tuberculosis but showed anti-cancer activities against human hepatocarcinoma （Hep G2） ATCC HB-8065 and human caucasian colon adenocarcinoma （Caco2） ATCC HTB-39 at concentration greater than 300 mcg/ml in DMSO （Dimethyl sulfoxide）.
基金supported by the National Natural Science Foundation of China(Grant No.51974173)the Natural Science Foundation of Shandong Province,China(Grant No.ZR2020QD122).
文摘The shear failure of intact rock under thermo-mechanical(TM)coupling conditions is common,such as in enhanced geothermal mining and deep mine construction.Under the effect of a continuous engineering disturbance,shear-formed fractures are prone to secondary instability,posing a severe threat to deep engineering.Although numerous studies regarding three-dimensional(3D)morphologies of fracture surfaces have been conducted,the understanding of shear-formed fractures under TM coupling conditions is limited.In this study,direct shear tests of intact granite under various TM coupling conditions were conducted,followed by 3D laser scanning tests of shear-formed fractures.Test results demonstrated that the peak shear strength of intact granite is positively correlated with the normal stress,whereas it is negatively correlated with the temperature.The internal friction angle and cohesion of intact granite significantly decrease with an increase in the temperature.The anisotropy,roughness value,and height of the asperities on the fracture surfaces are reduced as the normal stress increases,whereas their variation trends are the opposite as the temperature increases.The macroscopic failure mode of intact granite under TM coupling conditions is dominated by mixed tensileeshear and shear failures.As the normal stress increases,intragranular fractures are developed ranging from a local to a global distribution,and the macroscopic failure mode of intact granite changes from mixed tensileeshear to shear failure.Finally,3D morphological characteristics of the asperities on the shear-formed fracture surfaces were analyzed,and a quadrangular pyramid conceptual model representing these asperities was proposed and sufficiently verified.
文摘用扩展有限元法XFEM(Extended Finite Element Method)解决夹杂问题时,夹杂与基质的界面把单元分成若干部分。求单元刚度矩阵时,需要分别在这各个部分求积分。找到便于程序编制的描述各积分区域几何形状的方法是亟待解决的问题。本文把各积分区域的形成过程看成是圆对四边形的多次切割。考虑切剩区域与圆的关系时,把不完整的边仍看作完整的边,把切剩区域看成是四边形或是切去一两条边的四边形。采用排列组合的方法,把它们与圆的所有位置关系列了出来。
