Poleroviruses,which are distributed worldwide,infect many crops of economic importance and cause severe plant diseases.Brassica yellows virus(Br YV),which has three genotypes,A,B,and C,is a newly identified poleroviru...Poleroviruses,which are distributed worldwide,infect many crops of economic importance and cause severe plant diseases.Brassica yellows virus(Br YV),which has three genotypes,A,B,and C,is a newly identified polerovirus infecting crucifer crops in China,but its distribution is still unclear.Here,we report the distribution and prevalence levels of the three Br YV genotypes in crucifer crops in China.A total of 570 crucifer leaf samples randomly collected from 22 provinces,four ethnic minority autonomous regions,and three municipalities in China were tested for Br YV.RT-PCR detection showed that 97 of the field samples were positive for Br YV,and the average incidence of Br YV was 17.0%.The virus was detected in 22 provinces,with high incidences in north,northwest,and northeast China.The multiplex RT-PCR amplification of the three Br YV genotypes revealed that both single and mixed infections occurred.Among the Br YV infections,38.1% were mixinfected by more than two viral genotypes,and 8.2% samples were mix-infected by three viral genotypes.Our findings indicated a widespread prevalence of Br YV in China,and Br YV mixed infections with Turnip mosaic virus and Cucumber mosaic virus in crucifer crops are common.This study is the first large-scale survey of Br YV in crucifer crops in China.The information generated in this investigation will contribute to the national prevention and control of viral diseases.展开更多
In the finite element method,the numerical simulation of three-dimensional crack propagation is relatively rare,and it is often realized by commercial programs.In addition to the geometric complexity,the determination...In the finite element method,the numerical simulation of three-dimensional crack propagation is relatively rare,and it is often realized by commercial programs.In addition to the geometric complexity,the determination of the cracking direction constitutes a great challenge.In most cases,the local stress state provides the fundamental criterion to judge the presence of cracks and the direction of crack propagation.However,in the case of three-dimensional analysis,the coordination relationship between grid elements due to occurrence of cracks becomes a difficult problem for this method.In this paper,based on the extended finite element method,the stress-related function field is introduced into the calculation domain,and then the boundary value problem of the function is solved.Subsequently,the envelope surface of all propagation directions can be obtained at one time.At last,the possible surface can be selected as the direction of crack development.Based on the aforementioned procedure,such method greatly reduces the programming complexity of tracking the crack propagation.As a suitable method for simulating tension-induced failure,it can simulate multiple cracks simultaneously.展开更多
基金supported in part by the National Natural Science Foundation of China (31900139 and 31671995)the Key R&D Project of Shandong Province (2019GSF107095)。
文摘Poleroviruses,which are distributed worldwide,infect many crops of economic importance and cause severe plant diseases.Brassica yellows virus(Br YV),which has three genotypes,A,B,and C,is a newly identified polerovirus infecting crucifer crops in China,but its distribution is still unclear.Here,we report the distribution and prevalence levels of the three Br YV genotypes in crucifer crops in China.A total of 570 crucifer leaf samples randomly collected from 22 provinces,four ethnic minority autonomous regions,and three municipalities in China were tested for Br YV.RT-PCR detection showed that 97 of the field samples were positive for Br YV,and the average incidence of Br YV was 17.0%.The virus was detected in 22 provinces,with high incidences in north,northwest,and northeast China.The multiplex RT-PCR amplification of the three Br YV genotypes revealed that both single and mixed infections occurred.Among the Br YV infections,38.1% were mixinfected by more than two viral genotypes,and 8.2% samples were mix-infected by three viral genotypes.Our findings indicated a widespread prevalence of Br YV in China,and Br YV mixed infections with Turnip mosaic virus and Cucumber mosaic virus in crucifer crops are common.This study is the first large-scale survey of Br YV in crucifer crops in China.The information generated in this investigation will contribute to the national prevention and control of viral diseases.
基金Project(2017YFC0404802)supported by the National Key R&D Program of ChinaProjects(U1965206,51979143)supported by the National Natural Science Foundation of China。
文摘In the finite element method,the numerical simulation of three-dimensional crack propagation is relatively rare,and it is often realized by commercial programs.In addition to the geometric complexity,the determination of the cracking direction constitutes a great challenge.In most cases,the local stress state provides the fundamental criterion to judge the presence of cracks and the direction of crack propagation.However,in the case of three-dimensional analysis,the coordination relationship between grid elements due to occurrence of cracks becomes a difficult problem for this method.In this paper,based on the extended finite element method,the stress-related function field is introduced into the calculation domain,and then the boundary value problem of the function is solved.Subsequently,the envelope surface of all propagation directions can be obtained at one time.At last,the possible surface can be selected as the direction of crack development.Based on the aforementioned procedure,such method greatly reduces the programming complexity of tracking the crack propagation.As a suitable method for simulating tension-induced failure,it can simulate multiple cracks simultaneously.
