Severe convective weather can lead to a variety of disasters, but they are still difficult to be pre-warned and forecasted in the meteorological operation. This study generates a model based on the light gradient boos...Severe convective weather can lead to a variety of disasters, but they are still difficult to be pre-warned and forecasted in the meteorological operation. This study generates a model based on the light gradient boosting machine (LightGBM) algorithm using C-band radar echo products and ground observations, to identify and classify three major types of severe convective weather (</span><i><span style="font-family:Verdana;">i.e.</span></i><span style="font-family:Verdana;">, hail, short-term heavy rain (STHR), convective gust (CG)). The model evaluations show the LightGBM model performs well in the training set (2011-2017) and the testing set (2018) with the overall false identification ratio (FIR) of only 4.9% and 7.0%, respectively. Furthermore, the average probability of detection (POD), critical success index (CSI) and false alarm ratio (FAR) for the three types of severe convective weather in two sample sets are over 85%, 65% and lower than 30%, respectively. The LightGBM model and the storm cell identification and tracking (SCIT) product are then used to forecast the severe convective weather 15 - 60 minutes in advance. The average POD, CSI and FAR for the forecasts of the three types of severe convective weather are 57.4%, 54.7% and 38.4%, respectively, which are significantly higher than those of the manual work. Among the three types of severe convective weather, the STHR has the highest POD and CSI and the lowest FAR, while the skill scores for the hail and CG are similar. Therefore, the LightGBM model constructed in this paper is able to identify, classify and forecast the three major types of severe convective weather automatically with relatively high accuracy, and has a broad application prospect in the future automatic meteorological operation.展开更多
Melatonin has been shown to diminish edema in rats. Melatonin can be used to treat spinal cord injury. This study presumed that melatonin could relieve spinal cord edema and examined how it might act. Our experiments ...Melatonin has been shown to diminish edema in rats. Melatonin can be used to treat spinal cord injury. This study presumed that melatonin could relieve spinal cord edema and examined how it might act. Our experiments found that melatonin （100 mg/kg, i.p.） could reduce the water content of the spinal cord, and suppress the expression of aquaporin-4 and glial fibrillary acidic protein after spinal cord injury. This suggests that the mechanism by which melatonin alleviates the damage to the spinal cord by edema might be related to the expression of aquaporin-4 and glial fibrillary acidic protein.展开更多
More than half of the carbon pools in peatlands are stored in the soil layers below 30 cm,yet little is known about the carbon stabilizing factors at these depths.Although iron oxide minerals are considered to be impo...More than half of the carbon pools in peatlands are stored in the soil layers below 30 cm,yet little is known about the carbon stabilizing factors at these depths.Although iron oxide minerals are considered to be important for stabilizing organic carbon(OC),their role in the preservation of OC in peatlands,especially in the deep layers,is poorly understood.Here,we collected 1 m soil profiles from six peatlands in Central and West China to quantitatively study the vertical distribution characteristics of iron-bound OC(Fe-bound OC),and the influencing physicochemical properties of the soil.The results showed that the content of reactive iron(FeR)was enriched in the top layer and decreased gradually with depth.While Fe-bound OC was positively correlated with FeR,its concentration did not decrease with depth in the peat profile.There were no obvious trends in the distributions of FeR and Fe-bound OC with water level fluctuations in the peat profile.In addition,the proportion of Fe-bound OC to soil organic carbon in the deep peat(31 to 100 cm)was equivalent to that in the surface peat(0 to 30 cm),indicating that iron oxide mineral provides comparable protection of OC in both layers.According to upper estimates of global peatland carbon storage(612 Pg),it could be predicted that 23.81±11.75 Pg of OC is protected by association with FeR.These results indicated that iron oxide minerals are the effective"rusty sink"of OC sequestration in peatland,and a key factor for its long-term preservation.The results from this study make a valuable contribution to the carbon dynamics knowledgebase for peatlands,and provide a basis for improved predictive simulations.展开更多
Wetlands have the highest ecosystem service value among all terrestrial eco-systems.Among their ecosystem services,carbon sequestration and its potential ability to mitigate climate change have been extensively discus...Wetlands have the highest ecosystem service value among all terrestrial eco-systems.Among their ecosystem services,carbon sequestration and its potential ability to mitigate climate change have been extensively discussed recently,not only in the academic community but in media during COP27 of UNFCCC and COP14 of Ramsar.In particular,peatlands-peat-accumulating wetlands-accumulate 600 Gt C globally.展开更多
A novel two-stage reduction process for synthesis of ultrafine nickel powder with a high purity and low density in a fluidized bed reactor has been developed in this work. The raw ultraflne NiO particles are first pre...A novel two-stage reduction process for synthesis of ultrafine nickel powder with a high purity and low density in a fluidized bed reactor has been developed in this work. The raw ultraflne NiO particles are first pre-reduced using hydrogen at lower temperatures （340-400 ℃）, followed by further reduction at higher temperatures （500-600℃）. The self-agglomeration of Ni particles formed during low-temperature reduction decreases the sintering activity of the newly formed ultrafine Ni particles, leading to good fluidization quality, even for the subsequent high-temperature reduction process. The agglomerated Ni particles have a high Ni content （above 99wt%）, a low density （0.78g/cm^3） and a uniform particle size （approximately 100 μm）. A concept design for a novel two-stage fluidized bed reactor process used to produce high-purity Ni powder was also proposed. This approach may be extended to the synthesis of other ultrafine/nanosized metals or metal oxides through a fluidization method.展开更多
A simple protocol for reductive cleavage of C--O bond in diaryl and aryl methyl ethers was reported, in which Nail served as a reducing agent and KO Bu as a base and a radical initiator. The combination of Nail and KO...A simple protocol for reductive cleavage of C--O bond in diaryl and aryl methyl ethers was reported, in which Nail served as a reducing agent and KO Bu as a base and a radical initiator. The combination of Nail and KOBu displayed high efficiency for reductive cleavage of C-O bond in diaryl and awl ethers （e.g., dibenzofuran, diphe- nyl ether, anisole） without the hydrogenation of the aryl rings, in the absence of any other catalysts or ligands at 140 ℃, producing corresponding arenes and phenols. It was indicated that the reaction was under a radical mecha- nism.展开更多
The strictly contractive Peaceman-Rachford splitting method is one of effective methods for solving separable convex optimization problem, and the inertial proximal Peaceman-Rachford splitting method is one of its imp...The strictly contractive Peaceman-Rachford splitting method is one of effective methods for solving separable convex optimization problem, and the inertial proximal Peaceman-Rachford splitting method is one of its important variants. It is known that the convergence of the inertial proximal Peaceman- Rachford splitting method can be ensured if the relaxation factor in Lagrangian multiplier updates is underdetermined, which means that the steps for the Lagrangian multiplier updates are shrunk conservatively. Although small steps play an important role in ensuring convergence, they should be strongly avoided in practice. In this article, we propose a relaxed inertial proximal Peaceman- Rachford splitting method, which has a larger feasible set for the relaxation factor. Thus, our method provides the possibility to admit larger steps in the Lagrangian multiplier updates. We establish the global convergence of the proposed algorithm under the same conditions as the inertial proximal Peaceman-Rachford splitting method. Numerical experimental results on a sparse signal recovery problem in compressive sensing and a total variation based image denoising problem demonstrate the effectiveness of our method.展开更多
文摘Severe convective weather can lead to a variety of disasters, but they are still difficult to be pre-warned and forecasted in the meteorological operation. This study generates a model based on the light gradient boosting machine (LightGBM) algorithm using C-band radar echo products and ground observations, to identify and classify three major types of severe convective weather (</span><i><span style="font-family:Verdana;">i.e.</span></i><span style="font-family:Verdana;">, hail, short-term heavy rain (STHR), convective gust (CG)). The model evaluations show the LightGBM model performs well in the training set (2011-2017) and the testing set (2018) with the overall false identification ratio (FIR) of only 4.9% and 7.0%, respectively. Furthermore, the average probability of detection (POD), critical success index (CSI) and false alarm ratio (FAR) for the three types of severe convective weather in two sample sets are over 85%, 65% and lower than 30%, respectively. The LightGBM model and the storm cell identification and tracking (SCIT) product are then used to forecast the severe convective weather 15 - 60 minutes in advance. The average POD, CSI and FAR for the forecasts of the three types of severe convective weather are 57.4%, 54.7% and 38.4%, respectively, which are significantly higher than those of the manual work. Among the three types of severe convective weather, the STHR has the highest POD and CSI and the lowest FAR, while the skill scores for the hail and CG are similar. Therefore, the LightGBM model constructed in this paper is able to identify, classify and forecast the three major types of severe convective weather automatically with relatively high accuracy, and has a broad application prospect in the future automatic meteorological operation.
基金supported by the China Postdoctoral Science Foundation Grant,No.2014M552692
文摘Melatonin has been shown to diminish edema in rats. Melatonin can be used to treat spinal cord injury. This study presumed that melatonin could relieve spinal cord edema and examined how it might act. Our experiments found that melatonin （100 mg/kg, i.p.） could reduce the water content of the spinal cord, and suppress the expression of aquaporin-4 and glial fibrillary acidic protein after spinal cord injury. This suggests that the mechanism by which melatonin alleviates the damage to the spinal cord by edema might be related to the expression of aquaporin-4 and glial fibrillary acidic protein.
基金the Second Tibetan Plateau Scientific Expedition(2019QZKK0304)the Strategic Priority Research Program of Chinese Academy of Sciences(XDA2005010404)the Youth Science and Technology Innovation Team Program of Sichuan Province of China(2021JDTD011).
文摘More than half of the carbon pools in peatlands are stored in the soil layers below 30 cm,yet little is known about the carbon stabilizing factors at these depths.Although iron oxide minerals are considered to be important for stabilizing organic carbon(OC),their role in the preservation of OC in peatlands,especially in the deep layers,is poorly understood.Here,we collected 1 m soil profiles from six peatlands in Central and West China to quantitatively study the vertical distribution characteristics of iron-bound OC(Fe-bound OC),and the influencing physicochemical properties of the soil.The results showed that the content of reactive iron(FeR)was enriched in the top layer and decreased gradually with depth.While Fe-bound OC was positively correlated with FeR,its concentration did not decrease with depth in the peat profile.There were no obvious trends in the distributions of FeR and Fe-bound OC with water level fluctuations in the peat profile.In addition,the proportion of Fe-bound OC to soil organic carbon in the deep peat(31 to 100 cm)was equivalent to that in the surface peat(0 to 30 cm),indicating that iron oxide mineral provides comparable protection of OC in both layers.According to upper estimates of global peatland carbon storage(612 Pg),it could be predicted that 23.81±11.75 Pg of OC is protected by association with FeR.These results indicated that iron oxide minerals are the effective"rusty sink"of OC sequestration in peatland,and a key factor for its long-term preservation.The results from this study make a valuable contribution to the carbon dynamics knowledgebase for peatlands,and provide a basis for improved predictive simulations.
基金supported by the Second Tibetan Plateau Scientific Expedition(2019QZKK0304)the Strategic Priority Research Program of Chinese Academy of Sciences(XDA2005010404).
文摘Wetlands have the highest ecosystem service value among all terrestrial eco-systems.Among their ecosystem services,carbon sequestration and its potential ability to mitigate climate change have been extensively discussed recently,not only in the academic community but in media during COP27 of UNFCCC and COP14 of Ramsar.In particular,peatlands-peat-accumulating wetlands-accumulate 600 Gt C globally.
基金the National Special Project for Development of Major Scientific Equipment(2011YQ12003908)the China National Funds for Distinguished Young Scientists(21325628) for their financial support
文摘A novel two-stage reduction process for synthesis of ultrafine nickel powder with a high purity and low density in a fluidized bed reactor has been developed in this work. The raw ultraflne NiO particles are first pre-reduced using hydrogen at lower temperatures （340-400 ℃）, followed by further reduction at higher temperatures （500-600℃）. The self-agglomeration of Ni particles formed during low-temperature reduction decreases the sintering activity of the newly formed ultrafine Ni particles, leading to good fluidization quality, even for the subsequent high-temperature reduction process. The agglomerated Ni particles have a high Ni content （above 99wt%）, a low density （0.78g/cm^3） and a uniform particle size （approximately 100 μm）. A concept design for a novel two-stage fluidized bed reactor process used to produce high-purity Ni powder was also proposed. This approach may be extended to the synthesis of other ultrafine/nanosized metals or metal oxides through a fluidization method.
文摘A simple protocol for reductive cleavage of C--O bond in diaryl and aryl methyl ethers was reported, in which Nail served as a reducing agent and KO Bu as a base and a radical initiator. The combination of Nail and KOBu displayed high efficiency for reductive cleavage of C-O bond in diaryl and awl ethers （e.g., dibenzofuran, diphe- nyl ether, anisole） without the hydrogenation of the aryl rings, in the absence of any other catalysts or ligands at 140 ℃, producing corresponding arenes and phenols. It was indicated that the reaction was under a radical mecha- nism.
基金Acknowledgements This work was supported by the National Natural Science Foundation of China （Grant Nos. 11671116, 11271107, 91630202） and the Natural Science Foundation of Hebei Province of China （No. A2015202365）.
文摘The strictly contractive Peaceman-Rachford splitting method is one of effective methods for solving separable convex optimization problem, and the inertial proximal Peaceman-Rachford splitting method is one of its important variants. It is known that the convergence of the inertial proximal Peaceman- Rachford splitting method can be ensured if the relaxation factor in Lagrangian multiplier updates is underdetermined, which means that the steps for the Lagrangian multiplier updates are shrunk conservatively. Although small steps play an important role in ensuring convergence, they should be strongly avoided in practice. In this article, we propose a relaxed inertial proximal Peaceman- Rachford splitting method, which has a larger feasible set for the relaxation factor. Thus, our method provides the possibility to admit larger steps in the Lagrangian multiplier updates. We establish the global convergence of the proposed algorithm under the same conditions as the inertial proximal Peaceman-Rachford splitting method. Numerical experimental results on a sparse signal recovery problem in compressive sensing and a total variation based image denoising problem demonstrate the effectiveness of our method.
