Uncertainties in some key parameters in land surface models severely restrict the improvement of model capacity for successful simulation of surface-atmosphere interaction. These key parameters are related to soil moi...Uncertainties in some key parameters in land surface models severely restrict the improvement of model capacity for successful simulation of surface-atmosphere interaction. These key parameters are related to soil moisture and heat transfer and phy- sical processes in the vegetation canopy as well as other important aerodynamic processes. In the present study, measurements of surface-atmosphere interaction at two observation stations that are located in the typical semi-arid region of China, Tongyu Station in Jilin Province and Yuzhong Station in Gansu Province, are combined with the planetary boundary layer theory to estimate the value of two key aerodynamic parameters, i.e., surface roughness length zorn and excess resistance κB-1. Multiple parameterization schemes have been used in the study to obtain values for surface roughness length and excess resistance κB-1 at the two stations. Results indicate that Zorn has distinct seasonal and inter-annual variability. For the type of surface with low-height vegetation, there is a large difference between the default value of Zorn in the land surface model and that obtained from this study, κB-1 demonstrates a significant diurnal variation and seasonal variability. Using the modified scheme for the estimation of Zom and κB-1 in the land surface model, it is found that simulations of sensible heat flux over the semi-arid region have been greatly improved. These results suggest that it is necessary to further evaluate the default values of various parameters used in land surface models based on field measurements. The approach to combine field measurements with atmospheric boundary layer theory to retrieve realistic values for key parameters in land surface models presents a great potential in the improvement of modeling studies of surface-atmosphere interaction.展开更多
Detection of abnormal myocardial perfusion is crucial to the prognosis of patients with coronary artery disease(CAD)after they have undergone percutaneous coronary intervention(PCI).The objective of this study is to e...Detection of abnormal myocardial perfusion is crucial to the prognosis of patients with coronary artery disease(CAD)after they have undergone percutaneous coronary intervention(PCI).The objective of this study is to evaluate the effect of myocardial perfusion by three different methods—intra-coronary myocardial contrast echocardiography(ICMCE),corrected thrombolysis in myocardial infarction frame count(CTFC),and coronary blood flow velocity(BFV)—and to determine the value of these different methods in the evaluation of the effect of myocardial perfusion post-PCI.For the study sixty-eight patients were divided into four groups based on selective coronary angiography results:group A(normal coronary artery),group B(75%–95%coronary artery stenosis),group C(coronary artery stenosis>95%)and group D(acute total coronary occlusion).The effect of myocardial reperfusion was evaluated using the above mentioned three methods 15 min after PCI.IC-MCE was also performed before PCI in group D.The quantitative parameters of MCE involved:contrast peak intensity,time to peak intensity and area under the curve,representing myocardial blood volume,reperfusion velocity and myocardial blood flow,respectively.No difference was found in CTFC between the coronary artery stenosis group and the normal group.BFV was slower in group D than in group A(P<0.05).The myocardial blood volume and the myocardial blood flow of the IC-MCE quantitative parameters were markedly lower in group C compared with those in group A(P<0.05),and there were significant differences in the three MCE parameters between group D and group A(P<0.05).For those patients with acute or total occlusion,the levels of myocardial perfusion before and after PCI were similar,as determined by IC-MCE and visually analyzed from 61 segments(P<0.05).Quantitative IC-MCE evaluation of myocardial reperfusion is more accurate than with the other two methods.Moreover,with qualitative IC-MCE the level of myocardial reperfusion can be viewed directly and rapidly.Thus,the IC-MCE method is of great value to coronary artery disease(CAD)patients undergoing PCI,especially for those with acute myocardial infarction(AMI).展开更多
基金supported by the National Basic Research Program of China(Grant No.2011CB952002)the National Natural Science Foundation of China(Grant Nos.41475063+1 种基金41005047)Program for New Century Excellent Talents in University,and the Jiangsu Collaborative Innovation Center for Climate Change
文摘Uncertainties in some key parameters in land surface models severely restrict the improvement of model capacity for successful simulation of surface-atmosphere interaction. These key parameters are related to soil moisture and heat transfer and phy- sical processes in the vegetation canopy as well as other important aerodynamic processes. In the present study, measurements of surface-atmosphere interaction at two observation stations that are located in the typical semi-arid region of China, Tongyu Station in Jilin Province and Yuzhong Station in Gansu Province, are combined with the planetary boundary layer theory to estimate the value of two key aerodynamic parameters, i.e., surface roughness length zorn and excess resistance κB-1. Multiple parameterization schemes have been used in the study to obtain values for surface roughness length and excess resistance κB-1 at the two stations. Results indicate that Zorn has distinct seasonal and inter-annual variability. For the type of surface with low-height vegetation, there is a large difference between the default value of Zorn in the land surface model and that obtained from this study, κB-1 demonstrates a significant diurnal variation and seasonal variability. Using the modified scheme for the estimation of Zom and κB-1 in the land surface model, it is found that simulations of sensible heat flux over the semi-arid region have been greatly improved. These results suggest that it is necessary to further evaluate the default values of various parameters used in land surface models based on field measurements. The approach to combine field measurements with atmospheric boundary layer theory to retrieve realistic values for key parameters in land surface models presents a great potential in the improvement of modeling studies of surface-atmosphere interaction.
文摘Detection of abnormal myocardial perfusion is crucial to the prognosis of patients with coronary artery disease(CAD)after they have undergone percutaneous coronary intervention(PCI).The objective of this study is to evaluate the effect of myocardial perfusion by three different methods—intra-coronary myocardial contrast echocardiography(ICMCE),corrected thrombolysis in myocardial infarction frame count(CTFC),and coronary blood flow velocity(BFV)—and to determine the value of these different methods in the evaluation of the effect of myocardial perfusion post-PCI.For the study sixty-eight patients were divided into four groups based on selective coronary angiography results:group A(normal coronary artery),group B(75%–95%coronary artery stenosis),group C(coronary artery stenosis>95%)and group D(acute total coronary occlusion).The effect of myocardial reperfusion was evaluated using the above mentioned three methods 15 min after PCI.IC-MCE was also performed before PCI in group D.The quantitative parameters of MCE involved:contrast peak intensity,time to peak intensity and area under the curve,representing myocardial blood volume,reperfusion velocity and myocardial blood flow,respectively.No difference was found in CTFC between the coronary artery stenosis group and the normal group.BFV was slower in group D than in group A(P<0.05).The myocardial blood volume and the myocardial blood flow of the IC-MCE quantitative parameters were markedly lower in group C compared with those in group A(P<0.05),and there were significant differences in the three MCE parameters between group D and group A(P<0.05).For those patients with acute or total occlusion,the levels of myocardial perfusion before and after PCI were similar,as determined by IC-MCE and visually analyzed from 61 segments(P<0.05).Quantitative IC-MCE evaluation of myocardial reperfusion is more accurate than with the other two methods.Moreover,with qualitative IC-MCE the level of myocardial reperfusion can be viewed directly and rapidly.Thus,the IC-MCE method is of great value to coronary artery disease(CAD)patients undergoing PCI,especially for those with acute myocardial infarction(AMI).
