The North China Craton (NCC) is a classical example of ancient destroyed cratons.Since the initiation of the North China Craton Destruction Project by the National Natural Science Foundation of China,numerous studies ...The North China Craton (NCC) is a classical example of ancient destroyed cratons.Since the initiation of the North China Craton Destruction Project by the National Natural Science Foundation of China,numerous studies have been conducted on the timing,scale,and mechanism of this destruction through combined interdisciplinary research.Available data suggest that the destruction occurred mainly in the eastern NCC,whereas the western NCC was only locally modified.The sedimentation,magmatic activities and structural deformation after cratonization at ～1.8 Ga indicate that the NCC destruction took place in the Mesozoic with a peak age of ca 125 Ma.A global comparison suggests that most cratons on Earth are not destroyed,although they have commonly experienced lithospheric thinning;destruction is likely to occur only when the craton has been disturbed by oceanic subduction.The destruction of the NCC was coincident with globally active plate tectonics and high mantle temperatures during the Cretaceous.The subducted Pacific slab destabilized mantle convection beneath the eastern NCC,which resulted in cratonic destruction in the eastern NCC.Delamination and/or thermal-mechanical-chemical erosion resulted from the destabilization of mantle convection.展开更多
BACKGROUND:The present study aimed to explore the relationship between surgical methods,hemorrhage position,hemorrhage volume,surgical timing and treatment outcome of hypertensive intracerebral hemorrhage(HICH).METHOD...BACKGROUND:The present study aimed to explore the relationship between surgical methods,hemorrhage position,hemorrhage volume,surgical timing and treatment outcome of hypertensive intracerebral hemorrhage(HICH).METHODS:A total of 1 310 patients,who had been admitted to six hospitals from January 2004 to January 2008,were divided into six groups according to different surgical methods:craniotomy through bone fl ap(group A),craniotomy through a small bone window(group B),stereotactic drilling drainage(group C1 and group C2),neuron-endoscopy operation(group D) and external ventricular drainage(group E) in consideration of hemorrhage position,hemorrhage volume and clinical practice. A retrospective analysis was made of surgical timing and curative effect of the surgical methods.RESULTS:The effectiveness rate of the methods was 74.12% for 1 310 patients after onemonth follow-up. In this series,the disability rate was 44.82% 3–6 months after the operation. Among the 1 310 patients,241(18.40%) patients died after the operation. If hematoma volume was >80 mL and the operation was performed within 3 hours,the mortality rate of group A was signifi cantly lower than that of groups B,C,D,and E(P<0.05). If hematoma volume was 50–80 mL and the operation was performed within 6–12 hours,the mortality rate of groups B and D was lower than that of groups A,C and E(P<0.05). If hematoma volume was 20–50 mL and the operation was performed within 6–24 hours,the mortality rate of group C was lower than that of groups A,B and D(P<0.05).CONCLUSIONS:Craniotomy through a bone f lap is suitable for patients with a large hematoma and hernia of the brain. Stereotactic drilling drainage is suggested for patients with hematoma volume less than 80 mL. The curative effect of HICH individualized treatment would be improved via the suitable selection of operation time and surgical method according to the position and volume of hemorrhage.展开更多
As one of the four global satellite navigation systems,Compass not only enhances satellite visibility and availability for positioning,navigation and timing (PNT) for users in China and the surrounding areas,but also ...As one of the four global satellite navigation systems,Compass not only enhances satellite visibility and availability for positioning,navigation and timing (PNT) for users in China and the surrounding areas,but also improves PNT precision for global users.The improvements in satellite visibility and the dilution of precision are analyzed under GNSS compatibility and interoperation conditions.The contribution of the Compass satellite navigation system to global users,especially the benefits that users can acquire from the combination of Compass,GPS,GLONASS,and Galileo navigation systems,is analyzed using simulation data.展开更多
The first two Medium Earth Orbit(MEO) satellites of the third generation of Bei Dou satellite navigation System(BDS-3) were successfully launched on November 5, 2017. This historical launch starts the new era of the g...The first two Medium Earth Orbit(MEO) satellites of the third generation of Bei Dou satellite navigation System(BDS-3) were successfully launched on November 5, 2017. This historical launch starts the new era of the global navigation satellite system of Bei Dou. Before the first two satellites of BDS-3, a demonstration system for BDS-3 with five satellites,including two Inclined Geosynchronous Orbit satellites(IGSO) and three MEO satellites, was established between 2015 and2016 for testing the new payloads, new designed signals and new techniques. In the demonstration system, the new S frequency signal and satellite hydrogen clock as well as inter-satellite link(ISL) based on Ka-band signals with time-division multiple addresses(TDMA) were tested. This paper mainly analyzes the performances of the demonstration system, including the signalto-noise ratios, pseudorange errors and the multipath errors of the civilian signals of BDS-3. The qualities of signals in space,time synchronization and timing precision were tested as well. Most of the performances were compared with those of the regional Bei Dou satellite navigation system(BDS-2). At last, the performances of positioning, navigation and timing(PNT) of the future Bei Dou global system(BDS-3) were evaluated based on the signal quality of the present demonstration satellite system.展开更多
Femoral neck fractures account for nearly half of all hip fractures with the vast majority occurring in elderly patients after simple falls.Currently there may be sufficient evidence to support the routine use of hip ...Femoral neck fractures account for nearly half of all hip fractures with the vast majority occurring in elderly patients after simple falls.Currently there may be sufficient evidence to support the routine use of hip replacement surgery for low demand elderly patients in all but non-displaced and valgus impacted femoral neck fractures.However for the physiologically young patients,preservation of the natural hip anatomy and mechanics is a priority in management because of their high functional demands.The biomechanical challenges of femoral neck fixation and the vulnerability of the femoral head blood supply lead to a high incidence of non-union and osteonecrosis of the femoral head after internal fixation of displaced femoral neck fractures.Anatomic reduction and stable internal fixation are essentials in achieving the goals of treatment in this young patient population.Furthermore,other management variables such as surgical timing,the role of capsulotomy and the choice of implant for fixation remaincontroversial.This review will focus both on the demographics and injury profile of the young patient with femoral neck fractures and the current evidence behind the surgical management of these injuries as well as their major secondary complications.展开更多
Achieving both high yield and high nitrogen use efficiency （NUE） simultaneously has become a major challenge with increased global demand for food, depletion of natural resources, and deterioration of environment. A...Achieving both high yield and high nitrogen use efficiency （NUE） simultaneously has become a major challenge with increased global demand for food, depletion of natural resources, and deterioration of environment. As the greatest consumers of N fertilizer in the world, Chinese farmers have overused N, and there has been poor synchrony between crop N demand and N supply because of limited understanding of the N uptake-yield relationship. To address this problem, this study evaluated the total and dynamic N requirement for different yield ranges of two major crops （maize and wheat）, and suggested improvements to N management strategies. Whole-plant N aboveground uptake requirement per grain yield （Nreq） initially deceased with grain yield improvement and then stagnated, and yet most farmers still believed that more fertilizer and higher grain yield were synonymous. When maize yield increased from 〈 7.5 to 〉 12.0 Mg ha-I, Nreq decreased from 19.8 to 17.0 kg Mg-1 grain. For wheat, it decreased from 27.1 kg Mg-1 grain for grain yield 〈 4.5 Mg ha-1 to 22.7 kg Mg-1 grain for yield 〉 9.0 Mg ha-1. Meanwhile, the percentage of dry matter and N accumulation in the middle-late growing season increased significantly with grain yield, which indicated that N fertilization should be concentrated in the middle-late stage to match crop demand while farmers often applied the majority of N fertilizer either before sowing or during early growth stages. We accordingly developed an integrated soil-crop system management strategy that simultaneously increases both grain yield and NUE.展开更多
The initial collision between Indian and Asian continents marked the starting point for transformation of land-sea thermal contrast,uplift of the Tibet-Himalaya orogen,and climate change in Asia.In this paper,we revie...The initial collision between Indian and Asian continents marked the starting point for transformation of land-sea thermal contrast,uplift of the Tibet-Himalaya orogen,and climate change in Asia.In this paper,we review the published literatures from the past 30 years in order to draw consensus on the processes of initial collision and suturing that took place between the Indian and Asian plates.Following a comparison of the different methods that have been used to constrain the initial timing of collision,we propose that the tectono-sedimentary response in the peripheral foreland basin provides the most sensitive index of this event,and that paleomagnetism presents independent evidence as an alternative,reliable,and quantitative research method.In contrast to previous studies that have suggested collision between India and Asia started in Pakistan between ca.55 Ma and50 Ma and progressively closed eastwards,more recent researches have indicated that this major event first occurred in the center of the Yarlung Tsangpo suture zone(YTSZ) between ca.65 Ma and 63 Ma and then spreading both eastwards and westwards.While continental collision is a complicated process,including the processes of deformation,sedimentation,metamorphism,and magmatism,different researchers have tended to define the nature of this event based on their own understanding,an intuitive bias that has meant that its initial timing has remained controversial for decades.Here,we recommend the use of reconstructions of each geological event within the orogenic evolution sequence as this will allow interpretation of collision timing on the basis of multidisciplinary methods.展开更多
Bowel preparation is a core issue in colonoscopy,as it is closely related to the quality of the procedure.Patients often find that bowel preparation is the most unpleasant part of the examination.It is widely accepted...Bowel preparation is a core issue in colonoscopy,as it is closely related to the quality of the procedure.Patients often find that bowel preparation is the most unpleasant part of the examination.It is widely accepted that the quality of cleansing must be excellent to facilitate detecting neoplastic lesions.In spite of its importance and potential implications,until recently,bowel preparation has not been the subject of much study.The most commonly used agents are high-volume polyethylene glycol(PEG)electrolyte solution and sodium phosphate.There has been some confusion,even in published meta-analyses,regarding which of the two agents provides better cleansing.It is clear now that both PEG and sodium phosphate are effectivewhen administered with proper timing.Consequently,the timing of administration is recognized as one of the central factors to the quality of cleansing.The bowel preparation agent should be administered,at least in part,a few hours in advance of the colonoscopy.Several low volume agents are available,and either new or modified schedules with PEG that usually improve tolerance.Certain adjuvants can also be used to reduce the volume of PEG,or to improve the efficacy of other agents.Other factors apart from the choice of agent can improve the quality of bowel cleansing.For instance,the effect of diet before colonoscopy has not been completely clarified,but an exclusively liquid diet is probably not required,and a low-fiber diet may be preferable because it improves patient satisfaction and the quality of the procedure.Some patients,such as diabetics and persons with heart or kidney disease,require modified procedures and certain precautions.Bowel preparation for pediatric patients is also reviewed here.In such cases,PEG remains the most commonly used agent.As detecting neoplasia is not the main objective with these patients,less intensive preparation may suffice.Special considerations must be made for patients with inflammatory bowel disease,including safety and diagnostic issues,so that the most a展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos. 90814000,90814002)
文摘The North China Craton (NCC) is a classical example of ancient destroyed cratons.Since the initiation of the North China Craton Destruction Project by the National Natural Science Foundation of China,numerous studies have been conducted on the timing,scale,and mechanism of this destruction through combined interdisciplinary research.Available data suggest that the destruction occurred mainly in the eastern NCC,whereas the western NCC was only locally modified.The sedimentation,magmatic activities and structural deformation after cratonization at ～1.8 Ga indicate that the NCC destruction took place in the Mesozoic with a peak age of ca 125 Ma.A global comparison suggests that most cratons on Earth are not destroyed,although they have commonly experienced lithospheric thinning;destruction is likely to occur only when the craton has been disturbed by oceanic subduction.The destruction of the NCC was coincident with globally active plate tectonics and high mantle temperatures during the Cretaceous.The subducted Pacific slab destabilized mantle convection beneath the eastern NCC,which resulted in cratonic destruction in the eastern NCC.Delamination and/or thermal-mechanical-chemical erosion resulted from the destabilization of mantle convection.
基金supported by a grant from Shanghai Pudong New Area(PWZxkq2011-01)
文摘BACKGROUND:The present study aimed to explore the relationship between surgical methods,hemorrhage position,hemorrhage volume,surgical timing and treatment outcome of hypertensive intracerebral hemorrhage(HICH).METHODS:A total of 1 310 patients,who had been admitted to six hospitals from January 2004 to January 2008,were divided into six groups according to different surgical methods:craniotomy through bone fl ap(group A),craniotomy through a small bone window(group B),stereotactic drilling drainage(group C1 and group C2),neuron-endoscopy operation(group D) and external ventricular drainage(group E) in consideration of hemorrhage position,hemorrhage volume and clinical practice. A retrospective analysis was made of surgical timing and curative effect of the surgical methods.RESULTS:The effectiveness rate of the methods was 74.12% for 1 310 patients after onemonth follow-up. In this series,the disability rate was 44.82% 3–6 months after the operation. Among the 1 310 patients,241(18.40%) patients died after the operation. If hematoma volume was >80 mL and the operation was performed within 3 hours,the mortality rate of group A was signifi cantly lower than that of groups B,C,D,and E(P<0.05). If hematoma volume was 50–80 mL and the operation was performed within 6–12 hours,the mortality rate of groups B and D was lower than that of groups A,C and E(P<0.05). If hematoma volume was 20–50 mL and the operation was performed within 6–24 hours,the mortality rate of group C was lower than that of groups A,B and D(P<0.05).CONCLUSIONS:Craniotomy through a bone f lap is suitable for patients with a large hematoma and hernia of the brain. Stereotactic drilling drainage is suggested for patients with hematoma volume less than 80 mL. The curative effect of HICH individualized treatment would be improved via the suitable selection of operation time and surgical method according to the position and volume of hemorrhage.
基金supported by the National Natural Science Foundation of China (41020144004 and 40841021)the National High-Tech Research & Development Program of China (2007AA12Z331)
文摘As one of the four global satellite navigation systems,Compass not only enhances satellite visibility and availability for positioning,navigation and timing (PNT) for users in China and the surrounding areas,but also improves PNT precision for global users.The improvements in satellite visibility and the dilution of precision are analyzed under GNSS compatibility and interoperation conditions.The contribution of the Compass satellite navigation system to global users,especially the benefits that users can acquire from the combination of Compass,GPS,GLONASS,and Galileo navigation systems,is analyzed using simulation data.
基金supported by National Key R&D Program of China (Grant Nos. 2016YFB0501700, 2016YFB0501701)National Natural Science Foundation of China (Grant No. 41374019)
文摘The first two Medium Earth Orbit(MEO) satellites of the third generation of Bei Dou satellite navigation System(BDS-3) were successfully launched on November 5, 2017. This historical launch starts the new era of the global navigation satellite system of Bei Dou. Before the first two satellites of BDS-3, a demonstration system for BDS-3 with five satellites,including two Inclined Geosynchronous Orbit satellites(IGSO) and three MEO satellites, was established between 2015 and2016 for testing the new payloads, new designed signals and new techniques. In the demonstration system, the new S frequency signal and satellite hydrogen clock as well as inter-satellite link(ISL) based on Ka-band signals with time-division multiple addresses(TDMA) were tested. This paper mainly analyzes the performances of the demonstration system, including the signalto-noise ratios, pseudorange errors and the multipath errors of the civilian signals of BDS-3. The qualities of signals in space,time synchronization and timing precision were tested as well. Most of the performances were compared with those of the regional Bei Dou satellite navigation system(BDS-2). At last, the performances of positioning, navigation and timing(PNT) of the future Bei Dou global system(BDS-3) were evaluated based on the signal quality of the present demonstration satellite system.
文摘Femoral neck fractures account for nearly half of all hip fractures with the vast majority occurring in elderly patients after simple falls.Currently there may be sufficient evidence to support the routine use of hip replacement surgery for low demand elderly patients in all but non-displaced and valgus impacted femoral neck fractures.However for the physiologically young patients,preservation of the natural hip anatomy and mechanics is a priority in management because of their high functional demands.The biomechanical challenges of femoral neck fixation and the vulnerability of the femoral head blood supply lead to a high incidence of non-union and osteonecrosis of the femoral head after internal fixation of displaced femoral neck fractures.Anatomic reduction and stable internal fixation are essentials in achieving the goals of treatment in this young patient population.Furthermore,other management variables such as surgical timing,the role of capsulotomy and the choice of implant for fixation remaincontroversial.This review will focus both on the demographics and injury profile of the young patient with femoral neck fractures and the current evidence behind the surgical management of these injuries as well as their major secondary complications.
基金supported by the National Basic Research Program(973 Program) of China(No.2015CB150402)the National Maize Production System in China(No.CARS-02-24)+1 种基金the Special Fund for Agroscientific Research in the Public Interest of China (No.201103003)the Innovative Group Grant of the NSFC,China(No.31421092)
文摘Achieving both high yield and high nitrogen use efficiency （NUE） simultaneously has become a major challenge with increased global demand for food, depletion of natural resources, and deterioration of environment. As the greatest consumers of N fertilizer in the world, Chinese farmers have overused N, and there has been poor synchrony between crop N demand and N supply because of limited understanding of the N uptake-yield relationship. To address this problem, this study evaluated the total and dynamic N requirement for different yield ranges of two major crops （maize and wheat）, and suggested improvements to N management strategies. Whole-plant N aboveground uptake requirement per grain yield （Nreq） initially deceased with grain yield improvement and then stagnated, and yet most farmers still believed that more fertilizer and higher grain yield were synonymous. When maize yield increased from 〈 7.5 to 〉 12.0 Mg ha-I, Nreq decreased from 19.8 to 17.0 kg Mg-1 grain. For wheat, it decreased from 27.1 kg Mg-1 grain for grain yield 〈 4.5 Mg ha-1 to 22.7 kg Mg-1 grain for yield 〉 9.0 Mg ha-1. Meanwhile, the percentage of dry matter and N accumulation in the middle-late growing season increased significantly with grain yield, which indicated that N fertilization should be concentrated in the middle-late stage to match crop demand while farmers often applied the majority of N fertilizer either before sowing or during early growth stages. We accordingly developed an integrated soil-crop system management strategy that simultaneously increases both grain yield and NUE.
基金supported by the Chinese Academy of Sciences(Grant No.XDB03010401)the National Key Research and Development Plan(Grant No.2016YFC0600303)National Natural Science Foundation of China(Grant No.41490615)
文摘The initial collision between Indian and Asian continents marked the starting point for transformation of land-sea thermal contrast,uplift of the Tibet-Himalaya orogen,and climate change in Asia.In this paper,we review the published literatures from the past 30 years in order to draw consensus on the processes of initial collision and suturing that took place between the Indian and Asian plates.Following a comparison of the different methods that have been used to constrain the initial timing of collision,we propose that the tectono-sedimentary response in the peripheral foreland basin provides the most sensitive index of this event,and that paleomagnetism presents independent evidence as an alternative,reliable,and quantitative research method.In contrast to previous studies that have suggested collision between India and Asia started in Pakistan between ca.55 Ma and50 Ma and progressively closed eastwards,more recent researches have indicated that this major event first occurred in the center of the Yarlung Tsangpo suture zone(YTSZ) between ca.65 Ma and 63 Ma and then spreading both eastwards and westwards.While continental collision is a complicated process,including the processes of deformation,sedimentation,metamorphism,and magmatism,different researchers have tended to define the nature of this event based on their own understanding,an intuitive bias that has meant that its initial timing has remained controversial for decades.Here,we recommend the use of reconstructions of each geological event within the orogenic evolution sequence as this will allow interpretation of collision timing on the basis of multidisciplinary methods.
文摘Bowel preparation is a core issue in colonoscopy,as it is closely related to the quality of the procedure.Patients often find that bowel preparation is the most unpleasant part of the examination.It is widely accepted that the quality of cleansing must be excellent to facilitate detecting neoplastic lesions.In spite of its importance and potential implications,until recently,bowel preparation has not been the subject of much study.The most commonly used agents are high-volume polyethylene glycol(PEG)electrolyte solution and sodium phosphate.There has been some confusion,even in published meta-analyses,regarding which of the two agents provides better cleansing.It is clear now that both PEG and sodium phosphate are effectivewhen administered with proper timing.Consequently,the timing of administration is recognized as one of the central factors to the quality of cleansing.The bowel preparation agent should be administered,at least in part,a few hours in advance of the colonoscopy.Several low volume agents are available,and either new or modified schedules with PEG that usually improve tolerance.Certain adjuvants can also be used to reduce the volume of PEG,or to improve the efficacy of other agents.Other factors apart from the choice of agent can improve the quality of bowel cleansing.For instance,the effect of diet before colonoscopy has not been completely clarified,but an exclusively liquid diet is probably not required,and a low-fiber diet may be preferable because it improves patient satisfaction and the quality of the procedure.Some patients,such as diabetics and persons with heart or kidney disease,require modified procedures and certain precautions.Bowel preparation for pediatric patients is also reviewed here.In such cases,PEG remains the most commonly used agent.As detecting neoplasia is not the main objective with these patients,less intensive preparation may suffice.Special considerations must be made for patients with inflammatory bowel disease,including safety and diagnostic issues,so that the most a
