Changes in rainfall extremes pose a serious and additional threat to water resources planning and management, natural and artificial oasis stability, and sustainable development in the fragile ecosystems of arid inlan...Changes in rainfall extremes pose a serious and additional threat to water resources planning and management, natural and artificial oasis stability, and sustainable development in the fragile ecosystems of arid inland river basins. In this study, the trend and temporal variation of extreme precipitation are analyzed using daily precipitation datasets at 11 stations over the arid inland Heihe River basin in Northwest China from 1960 to 2011. Eight indices of extreme precipitation are studied. The results show statistically significant and large-magnitude increasing and decreasing trends for most indices, primarily in the Qilian Mountains and eastern Hexi Corridor. More frequent and intense rainfall extremes have occurred in the southern part of the desert area than in the northern portion. In general, the temporal variation in precipitation extremes has changed throughout the basin. Wet day precipitation and heavy precipitation days show statistically significant linear increasing trends and step changes in the Qilian Mountains and Hexi Corridor. Consecutive dry days have decreased obviously in the region in most years after approximately the late 1980s, but meanwhile very long dry spells have increased, especially in the Hexi Corridor. The probability density function indicates that very long wet spells have increased in the Qilian Mountains. The East Asian summer monsoon index and western Pacific subtropical high intensity index possess strong and significant negative and positive correlations with rainfall extremes, respectively. Changes in land surface characteristics and the increase in water vapor in the wet season have also contributed to the changes in precipitation extremes over the river basin.展开更多
Objective:To observe the effects of electroacupuncture(EA)pretreatment on motor function,cerebral blood flow,cerebral infarction volume,and vascular endothelial growth factor(VEGF)level in middle cerebral artery occlu...Objective:To observe the effects of electroacupuncture(EA)pretreatment on motor function,cerebral blood flow,cerebral infarction volume,and vascular endothelial growth factor(VEGF)level in middle cerebral artery occlusion(MCAO)model rats.Methods:Twenty-four male Sprague-Dawley rats were randomly divided into a normal group,a model group,and an EA group,with eight rats in each group.The middle cerebral artery ischemia-reperfusion model was established by the suture-occluded method in the model group and the EA group,while not in the normal group.The EA group was pretreated with EA at bilateral Fengchi(GB20)before model preparation,once a day for 30 min each time for a total of 7 d.The changes in the CatWalk gait parameters,modified Bederson neurological deficit score,cerebral blood flow,cerebral infarction volume after ischemia,and VEGF level in the brain tissue of rats in each group were observed.Results:Compared with the normal group,the modified Bederson neurological deficit score in the model group and the EA group increased after modeling(P<0.05),and the CatWalk gait parameters(one-leg stance duration,gait cadence,and gait cycle)were all changed(P<0.05).Compared with the model group,the modified Bederson neurological deficit score in the EA group decreased(P<0.05),and the CatWalk gait parameters improved(P<0.05).Immediately after ischemia,the cerebral blood flow in the normal group was greater than that in the model group and the EA group(P<0.05);after reperfusion,the cerebral blood flow in the EA group was greater than that in the model group(P<0.05).Compared with the normal group,the cerebral infarction volume in the model group and the EA group increased(P<0.05).Compared with the model group,the cerebral infarction volume in the EA group decreased(P<0.05).The expression level of VEGF-positive cells in the rat brain tissue in the model group was higher than that in the normal group(P<0.05),and was higher in the EA group than in the model group(P<0.05).Conclusion:EA pretreatment improves the limb motor function in MCAO model rats,alleviates the symptoms of neurological deficits,promotes the recovery of cerebral blood flow,reduces the cerebral infarction area after MCAO modeling,and increases the VEGF expression in the brain tissue.展开更多
基金supported by the Key Project of the Chinese Academy of Sciences (Grant No.KZZDEW-04-05)supported by the Australia–China Joint Research Centre on River Basin Management
文摘Changes in rainfall extremes pose a serious and additional threat to water resources planning and management, natural and artificial oasis stability, and sustainable development in the fragile ecosystems of arid inland river basins. In this study, the trend and temporal variation of extreme precipitation are analyzed using daily precipitation datasets at 11 stations over the arid inland Heihe River basin in Northwest China from 1960 to 2011. Eight indices of extreme precipitation are studied. The results show statistically significant and large-magnitude increasing and decreasing trends for most indices, primarily in the Qilian Mountains and eastern Hexi Corridor. More frequent and intense rainfall extremes have occurred in the southern part of the desert area than in the northern portion. In general, the temporal variation in precipitation extremes has changed throughout the basin. Wet day precipitation and heavy precipitation days show statistically significant linear increasing trends and step changes in the Qilian Mountains and Hexi Corridor. Consecutive dry days have decreased obviously in the region in most years after approximately the late 1980s, but meanwhile very long dry spells have increased, especially in the Hexi Corridor. The probability density function indicates that very long wet spells have increased in the Qilian Mountains. The East Asian summer monsoon index and western Pacific subtropical high intensity index possess strong and significant negative and positive correlations with rainfall extremes, respectively. Changes in land surface characteristics and the increase in water vapor in the wet season have also contributed to the changes in precipitation extremes over the river basin.
文摘Objective:To observe the effects of electroacupuncture(EA)pretreatment on motor function,cerebral blood flow,cerebral infarction volume,and vascular endothelial growth factor(VEGF)level in middle cerebral artery occlusion(MCAO)model rats.Methods:Twenty-four male Sprague-Dawley rats were randomly divided into a normal group,a model group,and an EA group,with eight rats in each group.The middle cerebral artery ischemia-reperfusion model was established by the suture-occluded method in the model group and the EA group,while not in the normal group.The EA group was pretreated with EA at bilateral Fengchi(GB20)before model preparation,once a day for 30 min each time for a total of 7 d.The changes in the CatWalk gait parameters,modified Bederson neurological deficit score,cerebral blood flow,cerebral infarction volume after ischemia,and VEGF level in the brain tissue of rats in each group were observed.Results:Compared with the normal group,the modified Bederson neurological deficit score in the model group and the EA group increased after modeling(P<0.05),and the CatWalk gait parameters(one-leg stance duration,gait cadence,and gait cycle)were all changed(P<0.05).Compared with the model group,the modified Bederson neurological deficit score in the EA group decreased(P<0.05),and the CatWalk gait parameters improved(P<0.05).Immediately after ischemia,the cerebral blood flow in the normal group was greater than that in the model group and the EA group(P<0.05);after reperfusion,the cerebral blood flow in the EA group was greater than that in the model group(P<0.05).Compared with the normal group,the cerebral infarction volume in the model group and the EA group increased(P<0.05).Compared with the model group,the cerebral infarction volume in the EA group decreased(P<0.05).The expression level of VEGF-positive cells in the rat brain tissue in the model group was higher than that in the normal group(P<0.05),and was higher in the EA group than in the model group(P<0.05).Conclusion:EA pretreatment improves the limb motor function in MCAO model rats,alleviates the symptoms of neurological deficits,promotes the recovery of cerebral blood flow,reduces the cerebral infarction area after MCAO modeling,and increases the VEGF expression in the brain tissue.
