The application of dams built upstream will change the input conditions, including water and sediment, of downstream fluvial system, and destroy previous dynamic quasi-equilibrium reached by channel streamflow, so ind...The application of dams built upstream will change the input conditions, including water and sediment, of downstream fluvial system, and destroy previous dynamic quasi-equilibrium reached by channel streamflow, so indispensable adjustments are necessary for downstream channel to adapt to the new water and sediment supply, leading the fluvial system to restore its previous equilibrium or reach a new equilibrium. Using about 50-year-long hydrological, sedimentary and cross-sectional data, temporal response processes of Toudaoguai cross-section located in the upper Yellow River to the operation of reservoirs built upstream are analyzed. The results show that the Toudaoguai cross-section change was influenced strongly by upstream reservoir operation and downstream channel bed armoring thereafter occurred gradually and extended to the reach below Sanhuhekou gauging station. Besides, median diameter of suspended sediment load experienced a three-stage change that is characterized by an increase at first, then a decrease and an increase again finally, which reflects the process of channel bed armoring that began at Qingtongxia reservoir and then gradually developed downstream to the reach below Sanhuhekou cross-section. Since the joint operation strategy of Longyangxia, Liujiaxia and Qingtongxia reservoirs was introduced in 1986, the three-stage change trend has become less evident than that in the time period between 1969 and 1986 when only Qingtongxia and Liujiaxia reservoirs were put into operation alone. In addition, since 1987, the extent of lateral migration and thalweg elevation change at Toudaoguai cross-section has reduced dramatically, cross-sectional profile and location tended to be stable, which is beneficial to the normal living for local people.展开更多
AIM:To determine an optimal cutoff value for abnormal splenic artery diameter/proper hepatic artery diameter(S/P) ratio in cirrhosis-induced portal hypertension.METHODS:Patients with cirrhosis and portal hypertension(...AIM:To determine an optimal cutoff value for abnormal splenic artery diameter/proper hepatic artery diameter(S/P) ratio in cirrhosis-induced portal hypertension.METHODS:Patients with cirrhosis and portal hypertension(n = 770) and healthy volunteers(n = 31) underwent volumetric computed tomography threedimensional vascular reconstruction to measure the internal diameters of the splenic artery and proper hepatic artery to calculate the S/P ratio.The cutoff value for abnormal S/P ratio was determined using receiver operating characteristic curve analysis,and the prevalence of abnormal S/P ratio and associations between abnormal S/P ratio and major complications of portal hypertension were studied using logistic regression.RESULTS:The receiver operating characteristic analysis showed that the cutoff points for abnormal splenic artery internal diameter and S/P ratio were > 5.19 mm and > 1.40,respectively.The sensitivity,specificity,positive predictive value,and negative predictive value were 74.2%,45.2%,97.1%,and 6.6%,respectively.The prevalence of an abnormal S/P ratio in the patients with cirrhosis and portal hypertension was 83.4%.Patients with a higher S/P ratio had a lower risk of developing ascites [odds ratio(OR) = 0.708,95%CI:0.508-0.986,P = 0.041] and a higher risk of developing esophageal and gastric varices(OR = 1.483,95%CI:1.010-2.175,P = 0.044) and forming collateral circulation(OR = 1.518,95%CI:1.033-2.230,P = 0.034).After splenectomy,the portal venous pressure and maximum and mean portal venous flow velocities were reduced,while the flow rate and maximum and minimum flow velocities of the hepatic artery were increased(P < 0.05).CONCLUSION:The prevalence of an abnormal S/P ratio is high in patients with cirrhosis and portal hypertension,and it can be used as an important marker of splanchnic hemodynamic disturbances.展开更多
The seedlings of Vernicia montana derived from seeds soaking with water (the first group)or 300 mg5L -1 mixed nitric_acid rare earth solution (the second group) were treated with various concentrations of mixed nitric...The seedlings of Vernicia montana derived from seeds soaking with water (the first group)or 300 mg5L -1 mixed nitric_acid rare earth solution (the second group) were treated with various concentrations of mixed nitric_acid rare earth solution by foliage spraying. The results showed that the seedling heights sprayed with 100 和 1 000 mg·L -1 of the first group and with 50 和 100 mg·L -1 of the second group were significantly higher than the controls, and the diameter at ground level sprayed with 300 mg·L -1 of the second group was significantly greater than the control, being 26.92% more than the latter; except for spraying with 0 mg5L -1 and 700～1 500 mg5L -1 of the second group, the seedling dry weight above ground of others was 29.13%～73.91% greater than the control, whereas the seedling dry weight under ground of others was 20.78%～116.88% greater than the control; the contents of chlorophyll a and chlorophyll b for all spraying seedling were 91.67%～191.67% and 87.5%～306.25% greater than the control, respectively, and soluble proteins and soluble sugars were 16.00%～179.78% and 10.73%～105.65% greater than the control, respectively. Compared with the control, the activity of SOD tended to increase, whereas the contents of MDA decreased. These indicated that spraying leaves with optimum concentration of mixed nitric_acid rare earth solution could markedly promote the growth of seedlings and improve resistance ability of V. montana seedlings to bad environment. On the whole, the effects of spraying the leaves of seedling with 50～500 mg5L -1 mixed nitric_acid rare earth solution, which were derived from seeds soaking with 300 mg·L -1 mixed nitric_acid rare earth solution, were good.展开更多
植物功能性状之间的关系是其提高自身空间资源利用能力的一种生态策略,反映了植物与环境协同适应的表型可塑性机制。本文利用Arc GIS建立研究区域的数字高程模型(DEM),并提取样地坡向数据,采用标准化主轴估计(standardized major axis e...植物功能性状之间的关系是其提高自身空间资源利用能力的一种生态策略,反映了植物与环境协同适应的表型可塑性机制。本文利用Arc GIS建立研究区域的数字高程模型(DEM),并提取样地坡向数据,采用标准化主轴估计(standardized major axis estimation,SMA)方法,研究了兰州市北山不同坡向人工林侧柏株高-冠幅和株高-胸径的异速生长关系。结果表明,侧柏胸径在各坡向上存在显著性差异(P<0.05),株高和冠幅在东坡和西坡之间无显著性差异(P>0.05);侧柏株高与冠幅的异速生长关系存在坡向差异,南坡冠幅的生长速率大于株高的生长速率,北坡冠幅的生长速率小于株高的生长速率,东坡和西坡株高、冠幅的生长速率相近;各坡向上侧柏胸径的生长速率均大于株高的生长速率,二者异速生长关系的坡向差异不明显(P>0.05)。侧柏冠幅、胸径与株高异速关系在各坡向上的不同表现,反映了异质性生境中植物主要构件的投资权衡机制。展开更多
基金National Natural Science Foundation of China, No.40771031 Thanks are expressed to the Yellow River Conservancy Commission and International Network on Erosion and Sedimentation for the permission of access to hydrometric data. We are also grateful to Dr. Wang Xiujie from Tianjin University for his generous help.
文摘The application of dams built upstream will change the input conditions, including water and sediment, of downstream fluvial system, and destroy previous dynamic quasi-equilibrium reached by channel streamflow, so indispensable adjustments are necessary for downstream channel to adapt to the new water and sediment supply, leading the fluvial system to restore its previous equilibrium or reach a new equilibrium. Using about 50-year-long hydrological, sedimentary and cross-sectional data, temporal response processes of Toudaoguai cross-section located in the upper Yellow River to the operation of reservoirs built upstream are analyzed. The results show that the Toudaoguai cross-section change was influenced strongly by upstream reservoir operation and downstream channel bed armoring thereafter occurred gradually and extended to the reach below Sanhuhekou gauging station. Besides, median diameter of suspended sediment load experienced a three-stage change that is characterized by an increase at first, then a decrease and an increase again finally, which reflects the process of channel bed armoring that began at Qingtongxia reservoir and then gradually developed downstream to the reach below Sanhuhekou cross-section. Since the joint operation strategy of Longyangxia, Liujiaxia and Qingtongxia reservoirs was introduced in 1986, the three-stage change trend has become less evident than that in the time period between 1969 and 1986 when only Qingtongxia and Liujiaxia reservoirs were put into operation alone. In addition, since 1987, the extent of lateral migration and thalweg elevation change at Toudaoguai cross-section has reduced dramatically, cross-sectional profile and location tended to be stable, which is beneficial to the normal living for local people.
基金Supported by Grants from Beijing Municipal Health Bureau, No.2011-2-18the Capital Health Development Special Funds, No.2011-2018-03
文摘AIM:To determine an optimal cutoff value for abnormal splenic artery diameter/proper hepatic artery diameter(S/P) ratio in cirrhosis-induced portal hypertension.METHODS:Patients with cirrhosis and portal hypertension(n = 770) and healthy volunteers(n = 31) underwent volumetric computed tomography threedimensional vascular reconstruction to measure the internal diameters of the splenic artery and proper hepatic artery to calculate the S/P ratio.The cutoff value for abnormal S/P ratio was determined using receiver operating characteristic curve analysis,and the prevalence of abnormal S/P ratio and associations between abnormal S/P ratio and major complications of portal hypertension were studied using logistic regression.RESULTS:The receiver operating characteristic analysis showed that the cutoff points for abnormal splenic artery internal diameter and S/P ratio were > 5.19 mm and > 1.40,respectively.The sensitivity,specificity,positive predictive value,and negative predictive value were 74.2%,45.2%,97.1%,and 6.6%,respectively.The prevalence of an abnormal S/P ratio in the patients with cirrhosis and portal hypertension was 83.4%.Patients with a higher S/P ratio had a lower risk of developing ascites [odds ratio(OR) = 0.708,95%CI:0.508-0.986,P = 0.041] and a higher risk of developing esophageal and gastric varices(OR = 1.483,95%CI:1.010-2.175,P = 0.044) and forming collateral circulation(OR = 1.518,95%CI:1.033-2.230,P = 0.034).After splenectomy,the portal venous pressure and maximum and mean portal venous flow velocities were reduced,while the flow rate and maximum and minimum flow velocities of the hepatic artery were increased(P < 0.05).CONCLUSION:The prevalence of an abnormal S/P ratio is high in patients with cirrhosis and portal hypertension,and it can be used as an important marker of splanchnic hemodynamic disturbances.
文摘The seedlings of Vernicia montana derived from seeds soaking with water (the first group)or 300 mg5L -1 mixed nitric_acid rare earth solution (the second group) were treated with various concentrations of mixed nitric_acid rare earth solution by foliage spraying. The results showed that the seedling heights sprayed with 100 和 1 000 mg·L -1 of the first group and with 50 和 100 mg·L -1 of the second group were significantly higher than the controls, and the diameter at ground level sprayed with 300 mg·L -1 of the second group was significantly greater than the control, being 26.92% more than the latter; except for spraying with 0 mg5L -1 and 700～1 500 mg5L -1 of the second group, the seedling dry weight above ground of others was 29.13%～73.91% greater than the control, whereas the seedling dry weight under ground of others was 20.78%～116.88% greater than the control; the contents of chlorophyll a and chlorophyll b for all spraying seedling were 91.67%～191.67% and 87.5%～306.25% greater than the control, respectively, and soluble proteins and soluble sugars were 16.00%～179.78% and 10.73%～105.65% greater than the control, respectively. Compared with the control, the activity of SOD tended to increase, whereas the contents of MDA decreased. These indicated that spraying leaves with optimum concentration of mixed nitric_acid rare earth solution could markedly promote the growth of seedlings and improve resistance ability of V. montana seedlings to bad environment. On the whole, the effects of spraying the leaves of seedling with 50～500 mg5L -1 mixed nitric_acid rare earth solution, which were derived from seeds soaking with 300 mg·L -1 mixed nitric_acid rare earth solution, were good.
文摘植物功能性状之间的关系是其提高自身空间资源利用能力的一种生态策略,反映了植物与环境协同适应的表型可塑性机制。本文利用Arc GIS建立研究区域的数字高程模型(DEM),并提取样地坡向数据,采用标准化主轴估计(standardized major axis estimation,SMA)方法,研究了兰州市北山不同坡向人工林侧柏株高-冠幅和株高-胸径的异速生长关系。结果表明,侧柏胸径在各坡向上存在显著性差异(P<0.05),株高和冠幅在东坡和西坡之间无显著性差异(P>0.05);侧柏株高与冠幅的异速生长关系存在坡向差异,南坡冠幅的生长速率大于株高的生长速率,北坡冠幅的生长速率小于株高的生长速率,东坡和西坡株高、冠幅的生长速率相近;各坡向上侧柏胸径的生长速率均大于株高的生长速率,二者异速生长关系的坡向差异不明显(P>0.05)。侧柏冠幅、胸径与株高异速关系在各坡向上的不同表现,反映了异质性生境中植物主要构件的投资权衡机制。
