AIM： To study the stability of portal hypertension （PHT） caused by partial ligation of the portal vein ligation （PVL） in a rat model.METHODS： Thirty male adult Wistar rats were divided into two groups： 10 in Gr...AIM： To study the stability of portal hypertension （PHT） caused by partial ligation of the portal vein ligation （PVL） in a rat model.METHODS： Thirty male adult Wistar rats were divided into two groups： 10 in Group Ⅰ received a sham operation; and 20 in Group Ⅱreceived partial PVL. Portal vein pressure （PVP） was measured at four time periods： before ligation, 2 wk, 6 wk and 10 wk postsurgery. Portal venography, blood sampling and liver and spleen pathological examinations were conducted at 10 wk after surgery.RESULTS： The PVP was 9.15± 0.58 cmH2O before ligation, and increased to 17.32 ±0.63 cmH2O 2 wk after PVL. By repeat measurement of the PVP in each rat, it was shown to remain elevated for 10 wk. There were no significant differences in the pressure measurements at 2 wk, 6 wk and 10 wk. Varices were found mainly in the mesenteric vein 2 wk after PVL, which were more obvious later, while these manifestations were similar at week 6 and week 10. Portal venography demonstrated the varices and collaterals. There was no significant change in liver pathology. The volume of the spleen was enlarged 2-fold after ligation, and the sinus of the spleen was enlarged due to congestion. Significant sinus endothelial cell proliferation was observed, but no evidence of hypersplenia was found on hemogram and biochemical examination.CONCLUSION： These findings suggest that a satisfactory prehepatic PHT rat model can be obtained by partial ligation of the portal vein, and this PHT rat model was stable for at least 10 wk.展开更多
Three groups of experiments on brittle-plastic transition and instability modes of granite were performed in a triaxial vessel with solid pressure medium at high temperature and high pressure. The results of experimen...Three groups of experiments on brittle-plastic transition and instability modes of granite were performed in a triaxial vessel with solid pressure medium at high temperature and high pressure. The results of experiments show that brittle faulting is the major failure mode at temperature <300℃, but crystal-plastic deformation is dominate at temperature >800℃, and there is a transition with increasing temperature from semi-brittle faulting to cataclastic flow and semi-brittle flow at temperatures of 300～800℃. So, temperature is the most influential factor in brittle-plastic transition of granite and confining pressure is the second factor. The results also show that progressive failure of granite occurs at lower pressure or high temperature where there is crystal plasticity, and sudden instability occurs at room temperature and high pressure (>300MPa) or high temperature and great pressure(550℃600MPa ～650℃700MPa), and a broad regime of quasi-sudden instability exists between the T-P condition of progressive failure and sudden instability. So, instability modes of granite depend simultaneously on the pressure and temperature.展开更多
基金Supported by National 10th 5-year Science Research Plan of China,No.2001BA705B10-15
文摘AIM： To study the stability of portal hypertension （PHT） caused by partial ligation of the portal vein ligation （PVL） in a rat model.METHODS： Thirty male adult Wistar rats were divided into two groups： 10 in Group Ⅰ received a sham operation; and 20 in Group Ⅱreceived partial PVL. Portal vein pressure （PVP） was measured at four time periods： before ligation, 2 wk, 6 wk and 10 wk postsurgery. Portal venography, blood sampling and liver and spleen pathological examinations were conducted at 10 wk after surgery.RESULTS： The PVP was 9.15± 0.58 cmH2O before ligation, and increased to 17.32 ±0.63 cmH2O 2 wk after PVL. By repeat measurement of the PVP in each rat, it was shown to remain elevated for 10 wk. There were no significant differences in the pressure measurements at 2 wk, 6 wk and 10 wk. Varices were found mainly in the mesenteric vein 2 wk after PVL, which were more obvious later, while these manifestations were similar at week 6 and week 10. Portal venography demonstrated the varices and collaterals. There was no significant change in liver pathology. The volume of the spleen was enlarged 2-fold after ligation, and the sinus of the spleen was enlarged due to congestion. Significant sinus endothelial cell proliferation was observed, but no evidence of hypersplenia was found on hemogram and biochemical examination.CONCLUSION： These findings suggest that a satisfactory prehepatic PHT rat model can be obtained by partial ligation of the portal vein, and this PHT rat model was stable for at least 10 wk.
文摘Three groups of experiments on brittle-plastic transition and instability modes of granite were performed in a triaxial vessel with solid pressure medium at high temperature and high pressure. The results of experiments show that brittle faulting is the major failure mode at temperature <300℃, but crystal-plastic deformation is dominate at temperature >800℃, and there is a transition with increasing temperature from semi-brittle faulting to cataclastic flow and semi-brittle flow at temperatures of 300～800℃. So, temperature is the most influential factor in brittle-plastic transition of granite and confining pressure is the second factor. The results also show that progressive failure of granite occurs at lower pressure or high temperature where there is crystal plasticity, and sudden instability occurs at room temperature and high pressure (>300MPa) or high temperature and great pressure(550℃600MPa ～650℃700MPa), and a broad regime of quasi-sudden instability exists between the T-P condition of progressive failure and sudden instability. So, instability modes of granite depend simultaneously on the pressure and temperature.
