Dynamic mixed-mode I/II crack growth under various engineering disturbances can result in rock failure and even catastrophic events.Nevertheless,the dynamic cracking behaviour of rock and fracture criterion for mixed-...Dynamic mixed-mode I/II crack growth under various engineering disturbances can result in rock failure and even catastrophic events.Nevertheless,the dynamic cracking behaviour of rock and fracture criterion for mixed-mode I/II remain poorly understood.Cracked straight-through Brazilian disc tests were performed on sandstone specimens to examine the effects of strain rate(ε˙)and loading angle(β)on the dynamic fracture behaviour of mixed-mode I/II using a split Hopkinson pressure bar system.The generalized maximum tangential stress(GMTS)criterion was modified by considering the influence ofβand crack propagation velocity(CPV)to estimate the dynamic fracture parameters.The results indicate that the CPV increases with increasingε˙,while remaining nearly independent ofβ.βandε˙strongly affect the dynamic mixed-mode fracturing process.The crack initiation angle changes slightly with increasingε˙,and it first increases and then stabilizes asβincreases.Whenβexceeds 60°andε˙is lower than approximately 10^(2)s^(−1),the crack initiation location transitions from the crack tip to the centre region of the crack.Whenε˙is greater than approximately 10^(2)s^(−1),the non-tip cracking disappears gradually.The dynamic failure characteristics of specimens can be divided into four main types,which occur successively with increasingβandε˙.Additionally,the dynamic stress intensity factors and crack initiation angles predicted by the modified GMTS criterion are generally consistent with the experimental results for different CPVs.This study provides valuable insights into the detailed dynamic mixed-mode cracking behaviour and fracture criterion of rock.展开更多
Bacterial adherence to the acquired dental pellicle, important in dental caries (caries), is mediated by receptor-adhesins such as salivary agglutinin binding to Streptococcus mutans antigen I/II (I/II). Ten selected ...Bacterial adherence to the acquired dental pellicle, important in dental caries (caries), is mediated by receptor-adhesins such as salivary agglutinin binding to Streptococcus mutans antigen I/II (I/II). Ten selected I/II epitopes were chosen to determine their reactivity to human salivary IgA. Previous studies suggested that a specific HLA biomarker group (HLA-DRB1*04) may have differential influence of immune responses to I/II. However, it was not known whether secretory IgA (SIgA) responses to the selected epitopes from HLA-DRB1*04 positive subjects were different compared to controls, or across other caries-related factors such as total IgA (TIgA). Thirty-two total subjects were matched according to HLA type, gender, ethnicity and age. HLA genotyping, oral bacterial, immunoglobulin and antibody analyses were performed. A large observed difference emerged with regard to the natural immune reservoir of TIgA in HLA-DRB1*04 positive subjects, specifically, a 27.6% reduction compared to controls. In contrast to all other epitopes studied, HLA-DRB1*04 positive subjects also exhibited reduced reactivity to I/II epitope 834-853. HLA-DRB1*04 positive subjects exhibited lower specific SIgA activity/TIgA to 834-853 and also a lower specific reactivity to 834-853/whole cell S. mutans UA159. Furthermore, HLA-DRB1*04 positive subjects exhibited lower responses to I/II in its entirety. The large observed difference in TIgA and the 834-853 reactivity pattern across multiple measures suggest potentially important connections pertaining to the link between HLA-DRB1*04 and caries.展开更多
The taxonomic status of Papilio maackii and P.syfanius has long been disputed.We conducted a molecular phylogenetic study to evaluate the taxonomic status of P.maackii and P.syfanius.A total of twenty-four P.maackii i...The taxonomic status of Papilio maackii and P.syfanius has long been disputed.We conducted a molecular phylogenetic study to evaluate the taxonomic status of P.maackii and P.syfanius.A total of twenty-four P.maackii individuals from six localities and sixteen P.syfanius individuals from two localities were analyzed.We sequenced the partial region of the CO-I gene（about 579 bp） and partial CO-II gene sequence（about 655bp） of the two species.The Kimura-2-Parameter distances among P.maackii and P.syfanius ranged from 0 to 0.6%.Fifteen haplotypes were obtained based on the combined data set.The results strongly supported that all P.maackii individuals and all P.syfanius individuals formed a large clade,and could not be divided into separated clades.This research indicated that the two species have only very recently undergone speciation.展开更多
基金funded by the National Natural Science Foundation of China(Grant Nos.52325404 and 52504094)Shenzhen University 2035 Initiative(Grant No.2022B001).
文摘Dynamic mixed-mode I/II crack growth under various engineering disturbances can result in rock failure and even catastrophic events.Nevertheless,the dynamic cracking behaviour of rock and fracture criterion for mixed-mode I/II remain poorly understood.Cracked straight-through Brazilian disc tests were performed on sandstone specimens to examine the effects of strain rate(ε˙)and loading angle(β)on the dynamic fracture behaviour of mixed-mode I/II using a split Hopkinson pressure bar system.The generalized maximum tangential stress(GMTS)criterion was modified by considering the influence ofβand crack propagation velocity(CPV)to estimate the dynamic fracture parameters.The results indicate that the CPV increases with increasingε˙,while remaining nearly independent ofβ.βandε˙strongly affect the dynamic mixed-mode fracturing process.The crack initiation angle changes slightly with increasingε˙,and it first increases and then stabilizes asβincreases.Whenβexceeds 60°andε˙is lower than approximately 10^(2)s^(−1),the crack initiation location transitions from the crack tip to the centre region of the crack.Whenε˙is greater than approximately 10^(2)s^(−1),the non-tip cracking disappears gradually.The dynamic failure characteristics of specimens can be divided into four main types,which occur successively with increasingβandε˙.Additionally,the dynamic stress intensity factors and crack initiation angles predicted by the modified GMTS criterion are generally consistent with the experimental results for different CPVs.This study provides valuable insights into the detailed dynamic mixed-mode cracking behaviour and fracture criterion of rock.
文摘Bacterial adherence to the acquired dental pellicle, important in dental caries (caries), is mediated by receptor-adhesins such as salivary agglutinin binding to Streptococcus mutans antigen I/II (I/II). Ten selected I/II epitopes were chosen to determine their reactivity to human salivary IgA. Previous studies suggested that a specific HLA biomarker group (HLA-DRB1*04) may have differential influence of immune responses to I/II. However, it was not known whether secretory IgA (SIgA) responses to the selected epitopes from HLA-DRB1*04 positive subjects were different compared to controls, or across other caries-related factors such as total IgA (TIgA). Thirty-two total subjects were matched according to HLA type, gender, ethnicity and age. HLA genotyping, oral bacterial, immunoglobulin and antibody analyses were performed. A large observed difference emerged with regard to the natural immune reservoir of TIgA in HLA-DRB1*04 positive subjects, specifically, a 27.6% reduction compared to controls. In contrast to all other epitopes studied, HLA-DRB1*04 positive subjects also exhibited reduced reactivity to I/II epitope 834-853. HLA-DRB1*04 positive subjects exhibited lower specific SIgA activity/TIgA to 834-853 and also a lower specific reactivity to 834-853/whole cell S. mutans UA159. Furthermore, HLA-DRB1*04 positive subjects exhibited lower responses to I/II in its entirety. The large observed difference in TIgA and the 834-853 reactivity pattern across multiple measures suggest potentially important connections pertaining to the link between HLA-DRB1*04 and caries.
基金National Natural Science Foundation of China (30870359)Anhui Scholar Special Fund in Science and Technology (KJ2009B015)
文摘The taxonomic status of Papilio maackii and P.syfanius has long been disputed.We conducted a molecular phylogenetic study to evaluate the taxonomic status of P.maackii and P.syfanius.A total of twenty-four P.maackii individuals from six localities and sixteen P.syfanius individuals from two localities were analyzed.We sequenced the partial region of the CO-I gene（about 579 bp） and partial CO-II gene sequence（about 655bp） of the two species.The Kimura-2-Parameter distances among P.maackii and P.syfanius ranged from 0 to 0.6%.Fifteen haplotypes were obtained based on the combined data set.The results strongly supported that all P.maackii individuals and all P.syfanius individuals formed a large clade,and could not be divided into separated clades.This research indicated that the two species have only very recently undergone speciation.
