Catchment erosion not only shapes various landforms of the earth’s surface but also affects the rates of chemical weathering and CO_(2) absorption by controlling the exposure of rock fragments,and thus acts as a regu...Catchment erosion not only shapes various landforms of the earth’s surface but also affects the rates of chemical weathering and CO_(2) absorption by controlling the exposure of rock fragments,and thus acts as a regulator of the global climate.Therefore,studying the occurrence and controlling factors of catchment erosion can improve our understanding of topographic evolution and long-term climate change.This paper introduces the“comminution age”method based on (^(234)U/^(238)U) of sediment detrital components and its applications to indicate the catchment erosion depth,which is widely applied to different depositional environments.In tectonically stable regions,where there is shallow erosion,the sediment output from the catchment is usually accompanied by a low (^(234)U/^(238)U).On the other hand,where there is deep erosion,the (^(234)U/^(238)U) of the downstream sediments is usually high.In tectonically active regions,deep erosion is common,and the sediment erosion process is subject to rapid material transport,such as landslide-induced sediment displacement.Since the sediment exposure history is short,the (^(234)U/^(238)U) of the detrital components is close to 1,thus reaching“secular equilibrium”.The comminution age method is promising in terms of tracing catchment erosion depths at the orbital scale.Furthermore,this method is also sensitive to the erosion changes caused by rapid climate changes and human activities.展开更多
Objective To investigate the stress distribution of the femur after cemented prosthetic replacement in aged patients with comminuted intertrochanteric fracture and to analyze the difference of stress distribution betw...Objective To investigate the stress distribution of the femur after cemented prosthetic replacement in aged patients with comminuted intertrochanteric fracture and to analyze the difference of stress distribution between cemented long展开更多
Radiogenic uranium isotope disequilibrium(^(234)U/^(238)U)has been used to trace a variety of Earth surface processes,and is usually attributed to direct recoil of^(234)Th and preferential dissolution of radioactively...Radiogenic uranium isotope disequilibrium(^(234)U/^(238)U)has been used to trace a variety of Earth surface processes,and is usually attributed to direct recoil of^(234)Th and preferential dissolution of radioactively damaged lattices at the mineral surface.However,the relative contribution of these two mechanisms in the natural environment remains unresolved,making it hard to use the extent of disequilibrium to quantify processes such as weathering.This study tests the contribution of preferential dissolution using well-characterized weathered moraines and river sediments from the southeastern Tibetan Plateau.The observations show that weathering of recent moraines where the contribution from direct recoil is negligible and is not associated with depletion of^(234)U at the mineral surface.It suggests a limited role for preferential dissolution in this setting.We attribute this lack of preferential dissolution to a near-to-equilibrium dissolution at the weathering interfaces,with little development of etch pits associated with radioactively damaged energetic sites.展开更多
基金supported by the National Key Research and Development Program of China (Grant No.2022YFF0800504)the National Natural Science Foundation of China (Grant Nos.41991324,42273057,42076063)+1 种基金the Natural Science Foundation of Shanghai (Grant Nos.20ZR1460400,21590712700)State Key Laboratory of Loess and Quaternary Geology,Institute of Earth Environment,CAS (Grant No.SKLLQG2222)。
文摘Catchment erosion not only shapes various landforms of the earth’s surface but also affects the rates of chemical weathering and CO_(2) absorption by controlling the exposure of rock fragments,and thus acts as a regulator of the global climate.Therefore,studying the occurrence and controlling factors of catchment erosion can improve our understanding of topographic evolution and long-term climate change.This paper introduces the“comminution age”method based on (^(234)U/^(238)U) of sediment detrital components and its applications to indicate the catchment erosion depth,which is widely applied to different depositional environments.In tectonically stable regions,where there is shallow erosion,the sediment output from the catchment is usually accompanied by a low (^(234)U/^(238)U).On the other hand,where there is deep erosion,the (^(234)U/^(238)U) of the downstream sediments is usually high.In tectonically active regions,deep erosion is common,and the sediment erosion process is subject to rapid material transport,such as landslide-induced sediment displacement.Since the sediment exposure history is short,the (^(234)U/^(238)U) of the detrital components is close to 1,thus reaching“secular equilibrium”.The comminution age method is promising in terms of tracing catchment erosion depths at the orbital scale.Furthermore,this method is also sensitive to the erosion changes caused by rapid climate changes and human activities.
文摘Objective To investigate the stress distribution of the femur after cemented prosthetic replacement in aged patients with comminuted intertrochanteric fracture and to analyze the difference of stress distribution between cemented long
基金supported by the Royal Society-Newton Advanced Fellowship(No.NA201244)the Natural Science Foundation of China(Nos.42061130212,41991321,41877351,41761144058,and 41730101)+2 种基金the Second Tibetan Plateau Scientific Expedition and Research(STEP)Program(No.2019QZKK0707)the Fundamental Research Funds for the Central Universities(No.0206-14380124)support from the China Scholarship Council Fellowship。
文摘Radiogenic uranium isotope disequilibrium(^(234)U/^(238)U)has been used to trace a variety of Earth surface processes,and is usually attributed to direct recoil of^(234)Th and preferential dissolution of radioactively damaged lattices at the mineral surface.However,the relative contribution of these two mechanisms in the natural environment remains unresolved,making it hard to use the extent of disequilibrium to quantify processes such as weathering.This study tests the contribution of preferential dissolution using well-characterized weathered moraines and river sediments from the southeastern Tibetan Plateau.The observations show that weathering of recent moraines where the contribution from direct recoil is negligible and is not associated with depletion of^(234)U at the mineral surface.It suggests a limited role for preferential dissolution in this setting.We attribute this lack of preferential dissolution to a near-to-equilibrium dissolution at the weathering interfaces,with little development of etch pits associated with radioactively damaged energetic sites.
