Na_(2)S,Na_(2)CO_(3),FeO,FeS and carbon were used to regulate the properties of slag or metal fractions,and their effects on metal growth and metal–slag separation behavior were investigated.The growth of ferronickel...Na_(2)S,Na_(2)CO_(3),FeO,FeS and carbon were used to regulate the properties of slag or metal fractions,and their effects on metal growth and metal–slag separation behavior were investigated.The growth of ferronickel grains can be enhanced by adding these additives,and Na_(2)S was the most effective.Na_(2)S,Na_(2)CO_(3) and FeO mainly affected the properties of slag,while carbon and FeS affected the metal fraction.The onset temperature of metal–slag separation was 1297℃ for the sample without additive,which was decreased to 1123 and 1101℃ after adding 3.30 wt.%Na_(2)S and 4.47 wt.%Na_(2)CO_(3),respectively.The onset temperature of metal–slag separation was mainly controlled by the slag fraction.The average apparent activation energy of metal grain growth was 125.32 kJ/mol without additive,and it decreased obviously after adding different additives.Na_(2)S also had the most remarkable effect on the decrease in activation energy.展开更多
We propose a simple pumping method to increase the effective population of cold atoms in the clock state and investigate the factors which affect the pumping efficiency in cold atom systems.We report the theory and de...We propose a simple pumping method to increase the effective population of cold atoms in the clock state and investigate the factors which affect the pumping efficiency in cold atom systems.We report the theory and demonstrate the corresponding experiment in an ^(87)Rb integrating sphere cold atom clock.The experimental results show that the population of cold atoms in the Zeeman sublevel|F=2,mF=0>is approximately 1.62 times that of the result using optical pumping alone.This method can also be applied to increase the effective population in any one of the target Zeeman sublevels in other cold atom systems.展开更多
Carbonyl iron(CI)particles as magnetic microwave absorption material often suffer from serious corrosion under corrosive environment which leads to performance deterioration.In this study,fluorin-containing acrylate t...Carbonyl iron(CI)particles as magnetic microwave absorption material often suffer from serious corrosion under corrosive environment which leads to performance deterioration.In this study,fluorin-containing acrylate type polymer network layers with thickness ranging from tens of nanometers to around one hundred nanometers were formed continuously around CI.The crosslinked coating layer(named FT)effectively increases CI’s thermal decomposition temperature by at least 34%.The FT-coated CI(named CI-FT)was able to resist both inorganic and organic corrosive media attacking efficiently compared with bare CI.The surface polymer network could also help CI withstand organic medium dissolution which proved the firmness of coating.Cyclic voltammetry(CV)test revealed that the coating layer could significantly reduce maximum oxidation current density of CI by more than 45 times.Tafel polarization study during CV tests also confirmed that thicker FT coating layer could help CI sample stabilize corrosion current density.Meanwhile,the surface coating also enhanced the impedance matching properties of CI as microwave absorber and the CI-FT samples demonstrated improved microwave absorption properties which degenerated little after corrosive medium soaking compared with that of CI.展开更多
Background:The novel coronavirus,severe acute respiratory syndrome coronavirus 2(SARS-CoV-2,also called 2019-nCoV)causes different morbidity risks to individuals in different age groups.This study attempts to quantify...Background:The novel coronavirus,severe acute respiratory syndrome coronavirus 2(SARS-CoV-2,also called 2019-nCoV)causes different morbidity risks to individuals in different age groups.This study attempts to quantify the age-specific transmissibility using a mathematical model.Methods:An epidemiological model with five compartments(susceptible-exposed-symptomatic-asymptomatic-recovered/removed[SEIAR])was developed based on observed transmission features.Coronavirus disease 2019(COVID-19)cases were divided into four age groups:group 1,those≤14years old;group 2,those 15 to 44years old;group 3,those 45 to 64years old;and group 4,those≥65 years old.The model was initially based on cases(including imported cases and secondary cases)collected in Hunan Province from January 5 to February 19,2020.Another dataset,from Jilin Province,was used to test the model.Results:The age-specific SEIAR model fitted the data well in each age group(P<0.001).In Hunan Province,the highest transmissibility was from age group 4 to 3(median:β43=7.71×10-9;SAR43=3.86×10-8),followed by group 3 to 4(median:β34=3.07×10-9;SAR34=1.53×10-8),group 2 to 2(median:β22=1.24×10-9;SAR22=6.21×10-9),and group 3 to 1(median:β31=4.10×10-10;SAR31=2.08×10-9).The lowest transmissibility was from age group 3 to 3(median:β33=1.64×10-19;SAR33=8.19×10-19),followed by group 4 to 4(median:β44=3.66×10-17;SAR44=1.83×10-16),group 3 to 2(median:β32=1.21×10-16;SAR32=6.06×10-16),and group 1 to 4(median:β14=7.20×10-14;SAR14=3.60×10-13).In Jilin Province,the highest transmissibility occurred from age group 4 to 4(median:β43=4.27×10-8;SAR43=2.13×10-7),followed by group 3 to 4(median:β34=1.81×10-8;SAR34=9.03×10-8).Conclusions:SARS-CoV-2 exhibits high transmissibility between middle-aged(45 to 64 years old)and elderly(≥65 years old)people.Children(≤14 years old)have very low susceptibility to COVID-19.This study will improve our understanding of the transmission feature of SARS-CoV-2 in different age groups and suggest the most prevention measures should be applied to middle-aged and elderly people.展开更多
Background: Reaching optimal vaccination rates is an essential public health strategy to control the coronavirus disease 2019 (COVID-19) pandemic. This study aimed to simulate the optimal vaccination strategy to contr...Background: Reaching optimal vaccination rates is an essential public health strategy to control the coronavirus disease 2019 (COVID-19) pandemic. This study aimed to simulate the optimal vaccination strategy to control the disease by developing an age-specific model based on the current transmission patterns of COVID-19 in Wuhan City, China.Methods: We collected two indicators of COVID-19, including illness onset data and age of confirmed case in Wuhan City, from December 2, 2019, to March 16, 2020. The reported cases were divided into four age groups: group 1, ≤ 14 years old;group 2, 15 to 44 years old;group 3, 44 to 64 years old;and group 4, ≥ 65 years old. An age-specific susceptible-exposed-symptomatic-asymptomatic-recovered/removed model was developed to estimate the transmissibility and simulate the optimal vaccination strategy. The effective reproduction number (R_(eff)) was used to estimate the transmission interaction in different age groups.Results: A total of 47 722 new cases were reported in Wuhan City from December 2, 2019, to March 16, 2020. Before the travel ban of Wuhan City, the highest transmissibility was observed among age group 2 (R_(eff) = 4.28), followed by group 2 to 3 (R_(eff) = 2.61), and group 2 to 4 (R_(eff) = 1.69). China should vaccinate at least 85% of the total population to interrupt transmission. The priority for controlling transmission should be to vaccinate 5% to 8% of individuals in age group 2 per day (ultimately vaccinated 90% of age group 2), followed by 10% of age group 3 per day (ultimately vaccinated 90% age group 3). However, the optimal vaccination strategy for reducing the disease severity identified individuals ≥ 65 years old as a priority group, followed by those 45-64 years old.Conclusions: Approximately 85% of the total population (nearly 1.2 billion people) should be vaccinated to build an immune barrier in China to safely consider removing border restrictions. Based on these results, we concluded that 90% of adults aged 15-64 years should first be vaccinated to prevent transmission in China.展开更多
基金support from the National Natural Science Foundation of China(No.51904047)the Fundamental and Frontier Research Project of Chongqing,China(No.cstc2020jcyj-msxmX0515)the State Key Laboratory of Complex Nonferrous Metal Resources Clean Utilization,China.
文摘Na_(2)S,Na_(2)CO_(3),FeO,FeS and carbon were used to regulate the properties of slag or metal fractions,and their effects on metal growth and metal–slag separation behavior were investigated.The growth of ferronickel grains can be enhanced by adding these additives,and Na_(2)S was the most effective.Na_(2)S,Na_(2)CO_(3) and FeO mainly affected the properties of slag,while carbon and FeS affected the metal fraction.The onset temperature of metal–slag separation was 1297℃ for the sample without additive,which was decreased to 1123 and 1101℃ after adding 3.30 wt.%Na_(2)S and 4.47 wt.%Na_(2)CO_(3),respectively.The onset temperature of metal–slag separation was mainly controlled by the slag fraction.The average apparent activation energy of metal grain growth was 125.32 kJ/mol without additive,and it decreased obviously after adding different additives.Na_(2)S also had the most remarkable effect on the decrease in activation energy.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61727821,61875215,and 11904408).
文摘We propose a simple pumping method to increase the effective population of cold atoms in the clock state and investigate the factors which affect the pumping efficiency in cold atom systems.We report the theory and demonstrate the corresponding experiment in an ^(87)Rb integrating sphere cold atom clock.The experimental results show that the population of cold atoms in the Zeeman sublevel|F=2,mF=0>is approximately 1.62 times that of the result using optical pumping alone.This method can also be applied to increase the effective population in any one of the target Zeeman sublevels in other cold atom systems.
基金financially supported by the National Natural Science Foundation of China(Nos.U19A2096,51903030,52021001)。
文摘Carbonyl iron(CI)particles as magnetic microwave absorption material often suffer from serious corrosion under corrosive environment which leads to performance deterioration.In this study,fluorin-containing acrylate type polymer network layers with thickness ranging from tens of nanometers to around one hundred nanometers were formed continuously around CI.The crosslinked coating layer(named FT)effectively increases CI’s thermal decomposition temperature by at least 34%.The FT-coated CI(named CI-FT)was able to resist both inorganic and organic corrosive media attacking efficiently compared with bare CI.The surface polymer network could also help CI withstand organic medium dissolution which proved the firmness of coating.Cyclic voltammetry(CV)test revealed that the coating layer could significantly reduce maximum oxidation current density of CI by more than 45 times.Tafel polarization study during CV tests also confirmed that thicker FT coating layer could help CI sample stabilize corrosion current density.Meanwhile,the surface coating also enhanced the impedance matching properties of CI as microwave absorber and the CI-FT samples demonstrated improved microwave absorption properties which degenerated little after corrosive medium soaking compared with that of CI.
基金This work was partly supported by the Open Research Fund of State Key Laboratory of Molecular Vaccinology and Molecular Diagnostics(SKLVD2019KF005)the Bill&Melinda Gates Foundation(INV-005834)+3 种基金the Science and Technology Program of Fujian Province(No:2020Y0002)the Xiamen New Coronavirus Prevention and Control Emergency Tackling Special Topic Program(No:3502Z2020YJ03)the Hunan Provincial Construction of Innovative Provinces Special Social Development Areas Key Research and Development Project(2020SK3012)the Chinese Academy of Medical Sciences Coronavirus Disease 2019 Science and Technology Research Project in 2020(2020HY320003).
文摘Background:The novel coronavirus,severe acute respiratory syndrome coronavirus 2(SARS-CoV-2,also called 2019-nCoV)causes different morbidity risks to individuals in different age groups.This study attempts to quantify the age-specific transmissibility using a mathematical model.Methods:An epidemiological model with five compartments(susceptible-exposed-symptomatic-asymptomatic-recovered/removed[SEIAR])was developed based on observed transmission features.Coronavirus disease 2019(COVID-19)cases were divided into four age groups:group 1,those≤14years old;group 2,those 15 to 44years old;group 3,those 45 to 64years old;and group 4,those≥65 years old.The model was initially based on cases(including imported cases and secondary cases)collected in Hunan Province from January 5 to February 19,2020.Another dataset,from Jilin Province,was used to test the model.Results:The age-specific SEIAR model fitted the data well in each age group(P<0.001).In Hunan Province,the highest transmissibility was from age group 4 to 3(median:β43=7.71×10-9;SAR43=3.86×10-8),followed by group 3 to 4(median:β34=3.07×10-9;SAR34=1.53×10-8),group 2 to 2(median:β22=1.24×10-9;SAR22=6.21×10-9),and group 3 to 1(median:β31=4.10×10-10;SAR31=2.08×10-9).The lowest transmissibility was from age group 3 to 3(median:β33=1.64×10-19;SAR33=8.19×10-19),followed by group 4 to 4(median:β44=3.66×10-17;SAR44=1.83×10-16),group 3 to 2(median:β32=1.21×10-16;SAR32=6.06×10-16),and group 1 to 4(median:β14=7.20×10-14;SAR14=3.60×10-13).In Jilin Province,the highest transmissibility occurred from age group 4 to 4(median:β43=4.27×10-8;SAR43=2.13×10-7),followed by group 3 to 4(median:β34=1.81×10-8;SAR34=9.03×10-8).Conclusions:SARS-CoV-2 exhibits high transmissibility between middle-aged(45 to 64 years old)and elderly(≥65 years old)people.Children(≤14 years old)have very low susceptibility to COVID-19.This study will improve our understanding of the transmission feature of SARS-CoV-2 in different age groups and suggest the most prevention measures should be applied to middle-aged and elderly people.
基金the Bill&Melinda Gates Foundation(Grant INV-005834 to T.C.)the Science and Technology Program of Fujian Province(Grant 2020Y0002 to T.C.)NHC Key Laboratory of Echinococcosis Preven‑tion and Control(Grant 2020WZK2001 to T.C.)。
文摘Background: Reaching optimal vaccination rates is an essential public health strategy to control the coronavirus disease 2019 (COVID-19) pandemic. This study aimed to simulate the optimal vaccination strategy to control the disease by developing an age-specific model based on the current transmission patterns of COVID-19 in Wuhan City, China.Methods: We collected two indicators of COVID-19, including illness onset data and age of confirmed case in Wuhan City, from December 2, 2019, to March 16, 2020. The reported cases were divided into four age groups: group 1, ≤ 14 years old;group 2, 15 to 44 years old;group 3, 44 to 64 years old;and group 4, ≥ 65 years old. An age-specific susceptible-exposed-symptomatic-asymptomatic-recovered/removed model was developed to estimate the transmissibility and simulate the optimal vaccination strategy. The effective reproduction number (R_(eff)) was used to estimate the transmission interaction in different age groups.Results: A total of 47 722 new cases were reported in Wuhan City from December 2, 2019, to March 16, 2020. Before the travel ban of Wuhan City, the highest transmissibility was observed among age group 2 (R_(eff) = 4.28), followed by group 2 to 3 (R_(eff) = 2.61), and group 2 to 4 (R_(eff) = 1.69). China should vaccinate at least 85% of the total population to interrupt transmission. The priority for controlling transmission should be to vaccinate 5% to 8% of individuals in age group 2 per day (ultimately vaccinated 90% of age group 2), followed by 10% of age group 3 per day (ultimately vaccinated 90% age group 3). However, the optimal vaccination strategy for reducing the disease severity identified individuals ≥ 65 years old as a priority group, followed by those 45-64 years old.Conclusions: Approximately 85% of the total population (nearly 1.2 billion people) should be vaccinated to build an immune barrier in China to safely consider removing border restrictions. Based on these results, we concluded that 90% of adults aged 15-64 years should first be vaccinated to prevent transmission in China.