The classical deviatoric hardening models are capable of characterizing the mechanical response of granular materials for a broad range of degrees of compaction.This work finds that it has limitations in accurately pr...The classical deviatoric hardening models are capable of characterizing the mechanical response of granular materials for a broad range of degrees of compaction.This work finds that it has limitations in accurately predicting the volumetric deformation characteristics under a wide range of confining/consolidation pressures.The issue stems from the pressure independent hardening law in the classical deviatoric hardening model.To overcome this problem,we propose a refined deviatoric hardening model in which a pressure-dependent hardening law is developed based on experimental observations.Comparisons between numerical results and laboratory triaxial tests indicate that the improved model succeeds in capturing the volumetric deformation behavior under various confining/consolidation pressure conditions for both dense and loose sands.Furthermore,to examine the importance of the improved deviatoric hardening model,it is combined with the bounding surface plasticity theory to investigate the mechanical response of loose sand under complex cyclic loadings and different initial consolidation pressures.It is proved that the proposed pressure-dependent deviatoric hardening law is capable of predicting the volumetric deformation characteristics to a satisfactory degree and plays an important role in the simulation of complex deformations for granular geomaterials.展开更多
目的研究意大利牛舌草(Anchusa italica Retz)不同极性溶剂萃取物对大鼠对缺氧/复氧心肌细胞(myocardial cells,MCs)氧化应激损伤保护作用的影响。方法模拟缺血再灌注损伤,建立体外培养心肌细胞缺氧/复氧模型,分为12组,正常对照组,缺氧...目的研究意大利牛舌草(Anchusa italica Retz)不同极性溶剂萃取物对大鼠对缺氧/复氧心肌细胞(myocardial cells,MCs)氧化应激损伤保护作用的影响。方法模拟缺血再灌注损伤,建立体外培养心肌细胞缺氧/复氧模型,分为12组,正常对照组,缺氧/复氧模型组,阳性对照组,处理组包括:高、中、低剂量乙酸乙酯萃取物+缺氧/复氧模型组;高、中、低剂量正丁醇萃取物+缺氧/复氧模型组;高、中、低剂量水萃取物+缺氧/复氧模型组。采用MTT法测定心肌细胞存活率;酶标仪检测细胞培养上清液中乳酸脱氢酶(LDH)水平及细胞内的丙二醛(MDA)含量和细胞内超氧化物歧化酶(SOD)的活力。结果与缺氧/复氧模型组比较,意大利牛舌草乙酸乙酯萃取物高剂量组、正丁醇萃取物高剂量组、水萃取物高剂量组心肌细胞存活率升高,LDH水平及MDA含量降低,SOD活力提高,差异有统计学意义(P<0.01)。结论意大利牛舌草乙酸乙酯萃取物、正丁醇萃取物、水萃取物对缺氧/复氧心肌细胞的损伤具有保护作用,其机制可能与平衡氧化应激产物和抗氧化应激的酶系统有关。展开更多
目的建立大鼠肠温孵液中意大利牛舌草4种成分(芦丁、山奈酚-3-O-芸香糖苷、水仙苷、迷迭香酸)的一测多评方法(Quantitative Analysis of Multi-components by Single-marker,QAMS)。方法采用聚酰胺柱色谱对意大利牛舌草粗提物进行纯化...目的建立大鼠肠温孵液中意大利牛舌草4种成分(芦丁、山奈酚-3-O-芸香糖苷、水仙苷、迷迭香酸)的一测多评方法(Quantitative Analysis of Multi-components by Single-marker,QAMS)。方法采用聚酰胺柱色谱对意大利牛舌草粗提物进行纯化。建立同时测定大鼠肠温孵液中意大利牛舌草提取物主要成分芦丁、山奈酚-3-O-芸香糖苷、水仙苷、迷迭香酸的高效液相色谱定量分析方法。以芦丁为内参物,测定大鼠肠温孵液中意大利牛舌草提取物主要成分芦丁与山奈酚-3-O-芸香糖苷、水仙苷、迷迭香酸的相对校正因子(Relative Correction Factor,RCF),利用RCF进行含量计算(计算值),并与外标法(External Standard Method,ESM)的测定结果(实测值)进行比较,对该方法进行可行性验证。结果采用ESM法测定8个批次的大鼠肠温孵液中意大利牛舌草提取物主要成分芦丁、山奈酚-3-O-芸香糖苷、水仙苷、迷迭香酸的平均含量分别为14.20、15.88、9.80、66.90 mg/g。在线性范围内,芦丁与山奈酚-3-O-芸香糖苷、水仙苷、迷迭香酸的RCF分别为0.983、1.101、0.843(RSD值均<2%)。利用RCF计算得山奈酚-3-O-芸香糖苷、水仙苷、迷迭香酸的平均含量分别为15.67、9.87、67.44 mg/g,两种方法的含量测定结果基本一致(相对偏差均<2%)。结论一测多评法简便、准确、可行,可用于大鼠肠温孵液中意大利牛舌草提取物山奈酚-3-O-芸香糖苷、水仙苷、迷迭香酸的含量测定。展开更多
基金the funding support from Basic Science Center Program for Multiphase Media Evolution in Hypergravity of the National Natural Science Foundation of China(Grant No.51988101).
文摘The classical deviatoric hardening models are capable of characterizing the mechanical response of granular materials for a broad range of degrees of compaction.This work finds that it has limitations in accurately predicting the volumetric deformation characteristics under a wide range of confining/consolidation pressures.The issue stems from the pressure independent hardening law in the classical deviatoric hardening model.To overcome this problem,we propose a refined deviatoric hardening model in which a pressure-dependent hardening law is developed based on experimental observations.Comparisons between numerical results and laboratory triaxial tests indicate that the improved model succeeds in capturing the volumetric deformation behavior under various confining/consolidation pressure conditions for both dense and loose sands.Furthermore,to examine the importance of the improved deviatoric hardening model,it is combined with the bounding surface plasticity theory to investigate the mechanical response of loose sand under complex cyclic loadings and different initial consolidation pressures.It is proved that the proposed pressure-dependent deviatoric hardening law is capable of predicting the volumetric deformation characteristics to a satisfactory degree and plays an important role in the simulation of complex deformations for granular geomaterials.
文摘目的研究意大利牛舌草(Anchusa italica Retz)不同极性溶剂萃取物对大鼠对缺氧/复氧心肌细胞(myocardial cells,MCs)氧化应激损伤保护作用的影响。方法模拟缺血再灌注损伤,建立体外培养心肌细胞缺氧/复氧模型,分为12组,正常对照组,缺氧/复氧模型组,阳性对照组,处理组包括:高、中、低剂量乙酸乙酯萃取物+缺氧/复氧模型组;高、中、低剂量正丁醇萃取物+缺氧/复氧模型组;高、中、低剂量水萃取物+缺氧/复氧模型组。采用MTT法测定心肌细胞存活率;酶标仪检测细胞培养上清液中乳酸脱氢酶(LDH)水平及细胞内的丙二醛(MDA)含量和细胞内超氧化物歧化酶(SOD)的活力。结果与缺氧/复氧模型组比较,意大利牛舌草乙酸乙酯萃取物高剂量组、正丁醇萃取物高剂量组、水萃取物高剂量组心肌细胞存活率升高,LDH水平及MDA含量降低,SOD活力提高,差异有统计学意义(P<0.01)。结论意大利牛舌草乙酸乙酯萃取物、正丁醇萃取物、水萃取物对缺氧/复氧心肌细胞的损伤具有保护作用,其机制可能与平衡氧化应激产物和抗氧化应激的酶系统有关。
文摘目的建立大鼠肠温孵液中意大利牛舌草4种成分(芦丁、山奈酚-3-O-芸香糖苷、水仙苷、迷迭香酸)的一测多评方法(Quantitative Analysis of Multi-components by Single-marker,QAMS)。方法采用聚酰胺柱色谱对意大利牛舌草粗提物进行纯化。建立同时测定大鼠肠温孵液中意大利牛舌草提取物主要成分芦丁、山奈酚-3-O-芸香糖苷、水仙苷、迷迭香酸的高效液相色谱定量分析方法。以芦丁为内参物,测定大鼠肠温孵液中意大利牛舌草提取物主要成分芦丁与山奈酚-3-O-芸香糖苷、水仙苷、迷迭香酸的相对校正因子(Relative Correction Factor,RCF),利用RCF进行含量计算(计算值),并与外标法(External Standard Method,ESM)的测定结果(实测值)进行比较,对该方法进行可行性验证。结果采用ESM法测定8个批次的大鼠肠温孵液中意大利牛舌草提取物主要成分芦丁、山奈酚-3-O-芸香糖苷、水仙苷、迷迭香酸的平均含量分别为14.20、15.88、9.80、66.90 mg/g。在线性范围内,芦丁与山奈酚-3-O-芸香糖苷、水仙苷、迷迭香酸的RCF分别为0.983、1.101、0.843(RSD值均<2%)。利用RCF计算得山奈酚-3-O-芸香糖苷、水仙苷、迷迭香酸的平均含量分别为15.67、9.87、67.44 mg/g,两种方法的含量测定结果基本一致(相对偏差均<2%)。结论一测多评法简便、准确、可行,可用于大鼠肠温孵液中意大利牛舌草提取物山奈酚-3-O-芸香糖苷、水仙苷、迷迭香酸的含量测定。
