The severe acute respiratory syndrome (SARS) caused tremendous damage to many Asia countries, espe- cially China. The transmission process and outbreak pattern of SARS is still not well understood. This study aims to ...The severe acute respiratory syndrome (SARS) caused tremendous damage to many Asia countries, espe- cially China. The transmission process and outbreak pattern of SARS is still not well understood. This study aims to find a simple model to describe the outbreak pattern of SARS cases by using SARS case data commonly released by governments. The outbreak pattern of cumulative SARS cases is expected to be a logistic type because the infection will be slowed down due to the increasing control effort by people and/or due to depletion of susceptible individuals. The increase rate of SARS cases is expected to decrease with the cumulative SARS cases, as described by the traditional logistical model, which is widely used in population dynamic studies. The in- stantaneous rate of increases were significantly and nega- tively correlated with the cumulative SARS cases in mainland of China (including Beijing, Hebei, Tianjin, Shanxi, the Autonomous Region of Inner Mongolia) and Singapore. The basic reproduction number R0 in Asia ranged from 2.0 to 5.6 (except for Taiwan, China). The R0 of Hebei and Tian- jin were much higher than that of Singapore, Hongkong, Beijing, Shanxi, Inner Mongolia, indicating SARS virus might have originated differently or new mutations occurred during transmission. We demonstrated that the outbreaks of SARS in many regions of Asia were well described by the logistic model, and the control measures implemented by governments are effective. The maximum instantaneous rate of increase, basic reproductive number, and maximum cu- mulative SARS cases were also calculated by using the logis- tic model.展开更多
In this study,a numerical study based on Euler equations and coupled with detail chemistry model is used to improve the propulsion performance and stability of the rotating detonation engine.The proposed fuel injectio...In this study,a numerical study based on Euler equations and coupled with detail chemistry model is used to improve the propulsion performance and stability of the rotating detonation engine.The proposed fuel injection called stratified injection functions by suppressing the isobaric combustion process occurring on the contact surface between fuel and detonation products,and thus the proportion of fuel consumed by detonation wave increases from 67%to 95%,leading to more self-pressure gain and lower entropy generation.A pre-mixed hydrogen-oxygen-nitrogen mixture is used as a reactive mixture.The computational results show that the propulsion performance and the operation stability of the engine with stratified injection are both improved,the temperature of the flow field is notably decreased,the specific impulse of the engine is improved by 16.3%,and the average temperature of the engine with stratified injection is reduced by 19.1%.展开更多
Production of reactive oxygen species(ROS)is a conserved immune response primarily mediated by NADPH oxidases(NOXs),also known in plants as respiratory burst oxidase homologs(RBOHs).Most microbe-associated molecular p...Production of reactive oxygen species(ROS)is a conserved immune response primarily mediated by NADPH oxidases(NOXs),also known in plants as respiratory burst oxidase homologs(RBOHs).Most microbe-associated molecular patterns(MAMPs)trigger a very fast and transient ROS burst in plants.However,recently,we found that lipopolysaccharides(LPS),a typical bacterial MAMP,triggered a biphasic ROS burst.In this study,we isolated mutants defective in LPS-triggered biphasic ROS burst(delt)in Arabidopsis,and cloned the DELT1 gene that was shown to encode RBOHD.In the delt1-2 allele,the antepenultimate residue,glutamic acid(E919),at the C-terminus of RBOHD was mutated to lysine(K).E919 is a highly conserved residue in NADPH oxidases,and a mutation of the corresponding residue E568 in human NOX2 has been reported to be one of the causes of chronic granulomatous disease.Consistently,we found that residue E919 was indispensable for RBOHD function in the MAMP-induced ROS burst and stomatal closure.It has been suggested that the mutation of this residue in other NADPH oxidases impairs the protein’s stability and complex assembly.However,we found that the E919K mutation did not affect RBOHD protein abundance or the ability of protein association,suggesting that the residue E919 in RBOHD might have a regulatory mechanism different from that of other NOXs.Taken together,our results confirm that the antepenultimate residue E is critical for NADPH oxidases and provide a new insight into the regulatory mechanisms of RBOHD.展开更多
文摘The severe acute respiratory syndrome (SARS) caused tremendous damage to many Asia countries, espe- cially China. The transmission process and outbreak pattern of SARS is still not well understood. This study aims to find a simple model to describe the outbreak pattern of SARS cases by using SARS case data commonly released by governments. The outbreak pattern of cumulative SARS cases is expected to be a logistic type because the infection will be slowed down due to the increasing control effort by people and/or due to depletion of susceptible individuals. The increase rate of SARS cases is expected to decrease with the cumulative SARS cases, as described by the traditional logistical model, which is widely used in population dynamic studies. The in- stantaneous rate of increases were significantly and nega- tively correlated with the cumulative SARS cases in mainland of China (including Beijing, Hebei, Tianjin, Shanxi, the Autonomous Region of Inner Mongolia) and Singapore. The basic reproduction number R0 in Asia ranged from 2.0 to 5.6 (except for Taiwan, China). The R0 of Hebei and Tian- jin were much higher than that of Singapore, Hongkong, Beijing, Shanxi, Inner Mongolia, indicating SARS virus might have originated differently or new mutations occurred during transmission. We demonstrated that the outbreaks of SARS in many regions of Asia were well described by the logistic model, and the control measures implemented by governments are effective. The maximum instantaneous rate of increase, basic reproductive number, and maximum cu- mulative SARS cases were also calculated by using the logis- tic model.
基金Project supported by the National Natural Science Foundation of China(No.11702329)the Open Project Program of the State Key Laboratory of Aerodynamics of China Aerodynamics Research and Development Center(CARDC)(No.SKLA20180101)+1 种基金the CARDC Fundamental and Frontier Technology Research Fund(No.PJD20180143)the Open Project Program of Rotor Aerodynamics Key Laboratory(No.RAL20180403),China。
文摘In this study,a numerical study based on Euler equations and coupled with detail chemistry model is used to improve the propulsion performance and stability of the rotating detonation engine.The proposed fuel injection called stratified injection functions by suppressing the isobaric combustion process occurring on the contact surface between fuel and detonation products,and thus the proportion of fuel consumed by detonation wave increases from 67%to 95%,leading to more self-pressure gain and lower entropy generation.A pre-mixed hydrogen-oxygen-nitrogen mixture is used as a reactive mixture.The computational results show that the propulsion performance and the operation stability of the engine with stratified injection are both improved,the temperature of the flow field is notably decreased,the specific impulse of the engine is improved by 16.3%,and the average temperature of the engine with stratified injection is reduced by 19.1%.
基金the National Natural Science Foundation of China(No.31622006)the Postdoctoral Science Foundation of China(Nos.2018M630683 and 2018T110601)
文摘Production of reactive oxygen species(ROS)is a conserved immune response primarily mediated by NADPH oxidases(NOXs),also known in plants as respiratory burst oxidase homologs(RBOHs).Most microbe-associated molecular patterns(MAMPs)trigger a very fast and transient ROS burst in plants.However,recently,we found that lipopolysaccharides(LPS),a typical bacterial MAMP,triggered a biphasic ROS burst.In this study,we isolated mutants defective in LPS-triggered biphasic ROS burst(delt)in Arabidopsis,and cloned the DELT1 gene that was shown to encode RBOHD.In the delt1-2 allele,the antepenultimate residue,glutamic acid(E919),at the C-terminus of RBOHD was mutated to lysine(K).E919 is a highly conserved residue in NADPH oxidases,and a mutation of the corresponding residue E568 in human NOX2 has been reported to be one of the causes of chronic granulomatous disease.Consistently,we found that residue E919 was indispensable for RBOHD function in the MAMP-induced ROS burst and stomatal closure.It has been suggested that the mutation of this residue in other NADPH oxidases impairs the protein’s stability and complex assembly.However,we found that the E919K mutation did not affect RBOHD protein abundance or the ability of protein association,suggesting that the residue E919 in RBOHD might have a regulatory mechanism different from that of other NOXs.Taken together,our results confirm that the antepenultimate residue E is critical for NADPH oxidases and provide a new insight into the regulatory mechanisms of RBOHD.
