Based on the stress field distribution rule of the mining floor under abutment pressure, we have established a simplified mechanical model, which contains multiple factors relating to activation and evolution of insid...Based on the stress field distribution rule of the mining floor under abutment pressure, we have established a simplified mechanical model, which contains multiple factors relating to activation and evolution of insidious water-conductive faults. The influence of normal and shear stresses on fault activation and effective shear stress distribution in the fault plane was acquired under mining conditions.Using fracture mechanics theory to calculate the stress intensity factor of an insidious fault front, we have derived the criterion for main fault activation. Results indicate that during the whole working face advance, transpressions are exerted on fault planes twice successively in opposite directions. In most cases, the second transpression is more likely to lead to fault activation. Activation is influenced by many factors, predominant among which are: burial depth of the insidious fault, friction angle of the fault plane, face advance direction and pore water pressure. Steep fault planes are more easily activated to induce a sustained water inrush in the face.展开更多
Background Non-pharmaceutical measures and travel restrictions have halted the spread of coronavirus disease 2019(COVID-19)and influenza.Nonetheless,with COVID-19 restrictions lifted,an unanticipated outbreak of the i...Background Non-pharmaceutical measures and travel restrictions have halted the spread of coronavirus disease 2019(COVID-19)and influenza.Nonetheless,with COVID-19 restrictions lifted,an unanticipated outbreak of the influ-enza B/Nictoria virus in late 2021 and another influenza H3N2 outbreak in mid-2022 occurred in Guangdong,southern China.The mechanism underlying this phenomenon remains unknown.To better prepare for potential influenza out-breaks during COVID-19 pandemic,we studied the molecular epidemiology and phylogenetics of influenza A(H3N2)and BNictoria that circulated during the COVID-19 pandemic in this region.Methods From January 1,2018 to December 31,2022,we collected throat swabs from 173,401 patients in Guang-dong who had acute respiratory tract infections.Influenza viruses in the samples were tested using reverse tran-scription-polymerase chain reaction,followed by subtype identification and sequencing of hemagglutinin(HA)and neuraminidase(NA)genes.Phylogenetic and genetic diversity analyses were performed on both genes from 403 samples.A rigorous molecular clock was aligned with the phylogenetic tree to measure the rate of viral evolution and the root-to-tip distance within strains in different years was assessed using regression curve models to determine the correlation.Results During the early period of COVID-19 control,various influenza viruses were nearly undetectable in respiratory specimens.When control measures were relaxed in January 2020,the influenza infection rate peaked at 4.94%(39/789)in December 2021,with the influenza B/Victoria accounting for 87.18%(34/39)of the total influenza cases.Six months later,the influenza infection rate again increased and peaked at 11.34%(255/2248)in June 2022;influenza A/H3N2 accounted for 94.51%(241/255)of the total influenza cases in autumn 2022.The diverse geographic distribution of HA genes of B/Nictoria and A/H3N2 had drastically reduced,and most strains originated from China.The rate of B/Victoria HA evolution(3.11×10^(-3),P<0.05)was 1.7 times faster than before the COVID-19 outbreak(1.80×10^(-3),P<0.05).Likewise,the H3N2 HA gene's evolution rate was 7.96×10^(-3)(P<0.05),which is 2.1 times faster than the strains'pre-COVID-19 evolution rate(3.81×10^(-3),P<0.05).Conclusions Despite the extraordinarily low detection rate of influenza infection,concealed influenza transmission may occur between individuals during strict COVID-19 control.This ultimately leads to the accumulation of viral mutations and accelerated evolution of H3N2 and BVictoria viruses.Monitoring the evolution of influenza may provide insights and alerts regarding potential epidemics in the future.展开更多
基金funded by the Major Basic Research and Development Program of China(No.2014CB046905)the Ph.D.Programs Foundation of Ministry of Education of China(No.20130095110018)
文摘Based on the stress field distribution rule of the mining floor under abutment pressure, we have established a simplified mechanical model, which contains multiple factors relating to activation and evolution of insidious water-conductive faults. The influence of normal and shear stresses on fault activation and effective shear stress distribution in the fault plane was acquired under mining conditions.Using fracture mechanics theory to calculate the stress intensity factor of an insidious fault front, we have derived the criterion for main fault activation. Results indicate that during the whole working face advance, transpressions are exerted on fault planes twice successively in opposite directions. In most cases, the second transpression is more likely to lead to fault activation. Activation is influenced by many factors, predominant among which are: burial depth of the insidious fault, friction angle of the fault plane, face advance direction and pore water pressure. Steep fault planes are more easily activated to induce a sustained water inrush in the face.
文摘Background Non-pharmaceutical measures and travel restrictions have halted the spread of coronavirus disease 2019(COVID-19)and influenza.Nonetheless,with COVID-19 restrictions lifted,an unanticipated outbreak of the influ-enza B/Nictoria virus in late 2021 and another influenza H3N2 outbreak in mid-2022 occurred in Guangdong,southern China.The mechanism underlying this phenomenon remains unknown.To better prepare for potential influenza out-breaks during COVID-19 pandemic,we studied the molecular epidemiology and phylogenetics of influenza A(H3N2)and BNictoria that circulated during the COVID-19 pandemic in this region.Methods From January 1,2018 to December 31,2022,we collected throat swabs from 173,401 patients in Guang-dong who had acute respiratory tract infections.Influenza viruses in the samples were tested using reverse tran-scription-polymerase chain reaction,followed by subtype identification and sequencing of hemagglutinin(HA)and neuraminidase(NA)genes.Phylogenetic and genetic diversity analyses were performed on both genes from 403 samples.A rigorous molecular clock was aligned with the phylogenetic tree to measure the rate of viral evolution and the root-to-tip distance within strains in different years was assessed using regression curve models to determine the correlation.Results During the early period of COVID-19 control,various influenza viruses were nearly undetectable in respiratory specimens.When control measures were relaxed in January 2020,the influenza infection rate peaked at 4.94%(39/789)in December 2021,with the influenza B/Victoria accounting for 87.18%(34/39)of the total influenza cases.Six months later,the influenza infection rate again increased and peaked at 11.34%(255/2248)in June 2022;influenza A/H3N2 accounted for 94.51%(241/255)of the total influenza cases in autumn 2022.The diverse geographic distribution of HA genes of B/Nictoria and A/H3N2 had drastically reduced,and most strains originated from China.The rate of B/Victoria HA evolution(3.11×10^(-3),P<0.05)was 1.7 times faster than before the COVID-19 outbreak(1.80×10^(-3),P<0.05).Likewise,the H3N2 HA gene's evolution rate was 7.96×10^(-3)(P<0.05),which is 2.1 times faster than the strains'pre-COVID-19 evolution rate(3.81×10^(-3),P<0.05).Conclusions Despite the extraordinarily low detection rate of influenza infection,concealed influenza transmission may occur between individuals during strict COVID-19 control.This ultimately leads to the accumulation of viral mutations and accelerated evolution of H3N2 and BVictoria viruses.Monitoring the evolution of influenza may provide insights and alerts regarding potential epidemics in the future.
