The annual number of deaths caused by hepatitis B virus(HBV)-related disease, including cirrhosis and hepatocellular carcinoma(HCC), is estimated as 887000. The reported prevalence of HBV reverse transcriptase(RT) mut...The annual number of deaths caused by hepatitis B virus(HBV)-related disease, including cirrhosis and hepatocellular carcinoma(HCC), is estimated as 887000. The reported prevalence of HBV reverse transcriptase(RT) mutation prior to treatment is varied and the impact of preexisting mutations on the treatment of na?ve patients remains controversial, and primarily depends on geographic factors, HBV genotypes, HBe Ag serostatus, HBV viral loads, disease progression, intergenotypic recombination and co-infection with HIV. Different sensitivity of detection methodology used could also affect their prevalence results. Several genotype-dependent HBV RT positions that can affect the emergence of drug resistance have also been reported. Eight mutations in RT(rtL80I, rtD134N, rtN139K/T/H, rtY141F, rtM204I/V, rtF221Y, rtI224V, and rtM309K) are significantly associated with HCC progression. HBe Ag-negative status, low viral load, and genotype C infection are significantly related to a higher frequency and prevalence of preexisting RT mutations. Preexisting mutations are most frequently found in the A-B interdomain of RT which overlaps with the HBs Ag "a" determinant region, mutations of which can lead to simultaneous viral immune escape. In conclusion, the presence of baseline RT mutations can affect drug treatment outcomes and disease progression in HBVinfected populations via modulation of viral fitness and host-immune responses.展开更多
This paper describes numerical simulation of hydraulic fracturing using fracture-based continuum modeling(FBCM)of coupled geomechanical-hydrological processes to evaluate a technique for high-density fracturing and fr...This paper describes numerical simulation of hydraulic fracturing using fracture-based continuum modeling(FBCM)of coupled geomechanical-hydrological processes to evaluate a technique for high-density fracturing and fracture caging.The simulations are innovative because of modeling discrete fractures explicitly in continuum analysis.A key advantage of FBCM is that fracture initiation and propagation are modeled explicitly without changing the domain grid(i.e.no re-meshing).Further,multiple realizations of a preexisting fracture distribution can be analyzed using the same domain grid.The simulated hydraulic fracturing technique consists of pressurizing multiple wells simultaneously:initially without permeating fluids into the rock,to seed fractures uniformly and at high density in the wall rock of the wells;followed by fluid injection to propagate the seeded fracture density hydraulically.FBCM combines the ease of continuum modeling with the potential accuracy of modeling discrete fractures and fracturing explicitly.Fractures are modeled as piecewise planar based on intersections with domain elements;fracture geometry stored as continuum properties is used to calculate parameters needed to model individual fractures;and rock behavior is modeled through tensorial aggregation of the behavior of discrete fractures and unfractured rock.Simulations are presented for previously unfractured rock and for rock with preexisting fractures of horizontal,shallow-dipping,steeply dipping,or vertical orientation.Simulations of a single-well model are used to determine the pattern and spacing for a multiple-well design.The results illustrate high-density fracturing and fracture caging through simultaneous fluid injection in multiple wells:for previously unfractured rock or rock with preexisting shallow-dipping or horizontal fractures,and in situ vertical compressive stress greater than horizontal.If preexisting fractures are steeply dipping or vertical,and considering the same in situ stress condition,well pressurization without fl展开更多
Recombinant adenovirus serotype 5(Ad5)vector has been widely applied in vaccine development targeting infectious diseases,such as Ebola virus disease and coronavirus disease 2019(COVID-19).However,the high prevalence ...Recombinant adenovirus serotype 5(Ad5)vector has been widely applied in vaccine development targeting infectious diseases,such as Ebola virus disease and coronavirus disease 2019(COVID-19).However,the high prevalence of preexisting anti-vector immunity compromises the immunogenicity of Ad5-based vaccines.Thus,there is a substantial unmet need to minimize preexisting immunity while improving the insert-induced immunity of Ad5 vectors.Herein,we address this need by utilizing biocompatible nanoparticles to modulate Ad5–host interactions.We show that positively charged human serum albumin nanoparticles((+)HSAnp),which are capable of forming a complex with Ad5,significantly increase the transgene expression of Ad5 in both coxsackievirus–adenovirus receptor-positive and-negative cells.Furthermore,in charge-and dose-dependent manners,Ad5/(+)HSAnp complexes achieve robust(up to227-fold higher)and long-term(up to 60 days)transgene expression in the lungs of mice following intranasal instillation.Importantly,in the presence of preexisting anti-Ad5 immunity,complexed Ad5-based Ebola and COVID-19 vaccines significantly enhance antigen-specific humoral response and mucosal immunity.These findings suggest that viral aggregation and charge modification could be leveraged to engineer enhanced viral vectors for vaccines and gene therapies.展开更多
The existence of defects in a rock mass is a vital factor complicating the mechanical response of the rock mass under stress.The characteristics of defects control the rock mass’s mechanical behaviors.This report rev...The existence of defects in a rock mass is a vital factor complicating the mechanical response of the rock mass under stress.The characteristics of defects control the rock mass’s mechanical behaviors.This report reviews the experimental studies on the influence of simulating the internal defects of rock mass’s mechanical properties.The effects of preexisting defects(shape,size,number,angle,and other factors)on the mechanical properties and failure modes of the rock are investigated from the perspectives of rock failure and fracture mechanics.The fracture propagation mechanisms of different defective rock masses are analyzed by studying the stress state of different defective rock masses under uniaxial compression.After the defective rock samples with varying inclination angles are destroyed,the relationship among the compressive strength,the fracture propagation,and the failure characteristics is explored.The primary findings are as follows.The increase in the size and number of defects rapidly damages the mechanical properties of the rock and intensifies defect penetration and expansion.The rock mechanics characteristics of fissured rocks with different inclination angles show two primary variations:one is a continuous increase,and the other is a decrease followed by an increase.This result is strongly related to the failure pattern of rocks with preexisting fissures.This investigation is crucial for further studying the failure modes of complex defective rock masses and the geotechnical engineering related to defective rocks.展开更多
The region between the preexisting and nascentmembranes of a cleaving Rana egg is a dense protrusionregion of nearly 40μm wide at 180°stage.Later,thisregion differentiate,into an upper part,a strip withlong, bra...The region between the preexisting and nascentmembranes of a cleaving Rana egg is a dense protrusionregion of nearly 40μm wide at 180°stage.Later,thisregion differentiate,into an upper part,a strip withlong, branched and randomly distributed protrusionswhich are derived largely from the preexistingmembrane,and a lower part,a band with microvilli.During 4-and 8-cel1 stages,the strip is almost vanishedand microvilli in the band is shortened.The nascentmembrane is smooth at the 180°stage,then a rough areaappears below the smooth region and quickly expands.Wheat germ agglutinin which can bind to preexistingmembrane interrupts the development of the regionbetween the preexisting and nascent membranes.Detergent,Brij,having the property to increase the areaof nascent membrane,does not interrupt the developmentof the region between the preexisting and nascentmembranes.展开更多
Four types of granite specimens were prepared and treated by chemical corrosion for 5 and 30 days,which were then used to carry out triaxial compression tests under different confining pressuresσ_(3).Type A is the in...Four types of granite specimens were prepared and treated by chemical corrosion for 5 and 30 days,which were then used to carry out triaxial compression tests under different confining pressuresσ_(3).Type A is the intact sample with no preexisting flaws.Types B and C are the samples containing two relatively low-dip flaws and two relatively high-dip flaws,respectively.Type D is the sample including both relatively low-dip and relatively high-dip flaws.The influences of pH value of chemical solutions,flaw distribution,corrosion time andσ_(3) on triaxial stress-strain curves and ultimate failure modes are analyzed and discussed.The results show that the pH value of the chemical solution,corrosion time and the arrangement of preexisting flaws play crucial roles in the cracking behaviors of granite specimens.Type A specimens have the largest peak axial deviatoric stress,followed by Type C,Type D,and Type B specimens,respectively.It is because the decrease in the inclination of preexisting flaws induces the weakening effect due to the decrease in the shadow area along the compaction direction.Under aσ_(3) of 5 MPa,the peak axial deviatoric stress drops by approximately 40.89%,29.08%,4.08%,and 23.53%for pH=2,4,7,and 12,respectively.For intact granite(Type A)specimens,the ultimate failure mode displays a typical shear mode.The connection of two secondary cracks initiated at the tips of preexisting cracks is always the ultimate failure and crack coalescence mode for Type B specimens.The ultimate failure and crack coalescence mode of Types C and D specimens are significantly affected by pH value of the chemical solution,corrosion time andσ_(3),which is different from those of Types A and B specimens due to the differences in flow distributions.展开更多
A validated particle flow code(PFC^(2D))-based model was developed to investigate the indirect tensile mechanical behavior of shale containing two central parallel cracks under Brazilian splitting test conditions.The ...A validated particle flow code(PFC^(2D))-based model was developed to investigate the indirect tensile mechanical behavior of shale containing two central parallel cracks under Brazilian splitting test conditions.The results show that preexisting cracks have a significant and insignificant influence on the tensile strength of shale under LPL and LVL conditions,respectively.When L≥10 mm,changing the L and H values has little effect on the tensile strength of shale.However,the inclusion of preexisting cracks have a positive effect on reducing the anisotropy of the shale specimens,and in the case of an L/D ratio of 0.3,the shale anisotropy is the lowest.Four failure modes were formed at differentβandθvalues under LPL conditions.In the case ofβ≥60°,the failure mode is mainly affected byβ,and whenβ≤45°,the failure mode is more complicated than in the case ofβ≥60°.Only three major failure modes were observed under LVL conditions;in the case of 45°≤β≤75°andθ≤30°,the most complex failure mode occurred.展开更多
Although the coronavirus disease 2019(COVID-19)epidemic is still ongoing,vaccination rates are rising slowly and related treatments and drugs are being developed.At the same time,there is increasing evidence of preexi...Although the coronavirus disease 2019(COVID-19)epidemic is still ongoing,vaccination rates are rising slowly and related treatments and drugs are being developed.At the same time,there is increasing evidence of preexisting immunity against severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)in humans,mainly consisting of preexisting antibodies and immune cells(including T cells and B cells).The presence of these antibodies is mainly due to the seasonal prevalence of four common coronavirus types,especially OC43 and HKU1.The accumulated relevant evidence has suggested that the target of antibodies is mainly the S2 subunit of S protein,followed by evolutionary conservative regions such as the nucleocapsid(N)protein.Additionally,preexisting memory T and B cells are also present in the population.Preexisting antibodies can help the body protect against SARS-CoV-2 infection,reduce the severity of COVID-19,and rapidly increase the immune response post-infection.These multiple effects can directly affect disease progression and even the likelihood of death in certain individuals.Besides the positive effects,preexisting immunity may also have negative consequences,such as antibody-dependent enhancement(ADE)and original antigenic sin(OAS),the prevalence of which needs to be further established.In the future,more research should be focused on evaluating the role of preexisting immunity in COVID-19 outcomes,adopting appropriate policies and strategies for fighting the pandemic,and vaccine development that considers preexisting immunity.展开更多
Steps are distinctive features for estimating the movement of the upper and lower block of faults.However,studies about the influence of steps as a special type of discontinuity on cracking behaviors and strength of r...Steps are distinctive features for estimating the movement of the upper and lower block of faults.However,studies about the influence of steps as a special type of discontinuity on cracking behaviors and strength of rock masses are limited.In this research,rock-like samples with steps and preexisting flaws were fabricated.Step height h and the inclination angle of gentle slope of the stepαwere set to different values.Direct shear tests were conducted on these samples under different normal stresses.The experimental results reveal that the inclination angle of the gentle slope of the stepα,step height h,and normal stress have an influence on the strength,crack initiation,and crack propagation of the samples.The experimental results show that crack behaviors and shear strength were affected by step inclination anglesαand step height h.As the normal stress increases,the improvement of the strength of samples with a large step height is larger than that of samples with a small step height,the improvement of the strength of samples withαof 10°is larger than that of samples withαof 0°and-10°.The discrete element method was used to simulate the shear test.Numerical results show five different types of displacement vectors,which can be used to determine whether the cracks are tensile cracks or shear cracks.The above conclusions can provide help for estimating mechanical properties and failure modes of rock masses with steps of different geometries.展开更多
Based on the new seismic and drilling data and the recent related research results,this paper systematically analyzes the diversity and complexity of evolution process of crustal lithosphere structure and basin struct...Based on the new seismic and drilling data and the recent related research results,this paper systematically analyzes the diversity and complexity of evolution process of crustal lithosphere structure and basin structure in the Pearl River Mouth Basin on the northern margin of the South China Sea.Three types of detachment faults of different structural levels exist:crust-mantle detachment,inter-crust detachment and upper crust detachment.It is considered that different types of extensional detachment control different subbasin structures.Many fault depressions controlled by upper crust detachment faults have been found in the Zhu I Depression located in the proximal zone.These detachment faults are usually reformed by magma emplacement or controlled by preexisting faults.Baiyun-Liwan Sag located in the hyperextension area shows different characteristics of internal structure.The Baiyun main sag with relative weak magmatism transformation is a wide-deep fault depression,which is controlled by crust-mantle detachment system.Extensive magmatism occurred in the eastern and southwest fault steps of the Baiyun Sag after Middle Eocene,and the crust ductile extensional deformation resulted in wide-shallow fault depression controlled by the upper crust detachment fault.Based on the classical lithosphere extensional breaking and basin tectonic evolution in the Atlantic margin,it is believed that the magmatic activities and pre-existing structures in the Mesozoic subduction continental margin background are important controlling factors for the diversified continental margin faulted structures in the northern South China Sea.展开更多
Shallow seismic profiling in meizoseismal area of Xingtai earthquakes, phase division of Cenozoic movement of deep and shallow structures, analysis of characteristics of crustal and upper mantle structure, and compara...Shallow seismic profiling in meizoseismal area of Xingtai earthquakes, phase division of Cenozoic movement of deep and shallow structures, analysis of characteristics of crustal and upper mantle structure, and comparative study on parameters of seismic sources indicate that the listric faults controlling the development of early Tertiary basin-range structure and eastward gently-dipping detachment below it in the Xingtai epicentral area are not related to the occurrence of Xingtai earthquakes. The Xingtai earthquake swarm is a product of three-dimensional fracture process in which the discontinuous "deep faults", separated by NW-trending faults or by transverse barriers, successively tore, fractured, and propagated upward and, hence, caused the stress between the adjacent deep faults to migrate and load under the action of latest tectonic stress field. The Xingtai seismogenic fault represents a " newly generated fault" resulted from the upward tearing and propagation of the preexisting crustal " deep fault".展开更多
基金Supported by the Korea Health Technology R&D Project through the Korea Health Industry Development Institute and the Ministry of Health and Welfare,South Korea,No.HI14C0955
文摘The annual number of deaths caused by hepatitis B virus(HBV)-related disease, including cirrhosis and hepatocellular carcinoma(HCC), is estimated as 887000. The reported prevalence of HBV reverse transcriptase(RT) mutation prior to treatment is varied and the impact of preexisting mutations on the treatment of na?ve patients remains controversial, and primarily depends on geographic factors, HBV genotypes, HBe Ag serostatus, HBV viral loads, disease progression, intergenotypic recombination and co-infection with HIV. Different sensitivity of detection methodology used could also affect their prevalence results. Several genotype-dependent HBV RT positions that can affect the emergence of drug resistance have also been reported. Eight mutations in RT(rtL80I, rtD134N, rtN139K/T/H, rtY141F, rtM204I/V, rtF221Y, rtI224V, and rtM309K) are significantly associated with HCC progression. HBe Ag-negative status, low viral load, and genotype C infection are significantly related to a higher frequency and prevalence of preexisting RT mutations. Preexisting mutations are most frequently found in the A-B interdomain of RT which overlaps with the HBs Ag "a" determinant region, mutations of which can lead to simultaneous viral immune escape. In conclusion, the presence of baseline RT mutations can affect drug treatment outcomes and disease progression in HBVinfected populations via modulation of viral fitness and host-immune responses.
文摘This paper describes numerical simulation of hydraulic fracturing using fracture-based continuum modeling(FBCM)of coupled geomechanical-hydrological processes to evaluate a technique for high-density fracturing and fracture caging.The simulations are innovative because of modeling discrete fractures explicitly in continuum analysis.A key advantage of FBCM is that fracture initiation and propagation are modeled explicitly without changing the domain grid(i.e.no re-meshing).Further,multiple realizations of a preexisting fracture distribution can be analyzed using the same domain grid.The simulated hydraulic fracturing technique consists of pressurizing multiple wells simultaneously:initially without permeating fluids into the rock,to seed fractures uniformly and at high density in the wall rock of the wells;followed by fluid injection to propagate the seeded fracture density hydraulically.FBCM combines the ease of continuum modeling with the potential accuracy of modeling discrete fractures and fracturing explicitly.Fractures are modeled as piecewise planar based on intersections with domain elements;fracture geometry stored as continuum properties is used to calculate parameters needed to model individual fractures;and rock behavior is modeled through tensorial aggregation of the behavior of discrete fractures and unfractured rock.Simulations are presented for previously unfractured rock and for rock with preexisting fractures of horizontal,shallow-dipping,steeply dipping,or vertical orientation.Simulations of a single-well model are used to determine the pattern and spacing for a multiple-well design.The results illustrate high-density fracturing and fracture caging through simultaneous fluid injection in multiple wells:for previously unfractured rock or rock with preexisting shallow-dipping or horizontal fractures,and in situ vertical compressive stress greater than horizontal.If preexisting fractures are steeply dipping or vertical,and considering the same in situ stress condition,well pressurization without fl
基金supported in part by the grant from National Natural Science Foundation of China(82171818,81703048,82041019,and 82101919)the grant from Defense Industrial Technology Development Program of China(JCKY2020802B001)Beijing Municipal Science and Technology Commission(Z201100005420024)。
文摘Recombinant adenovirus serotype 5(Ad5)vector has been widely applied in vaccine development targeting infectious diseases,such as Ebola virus disease and coronavirus disease 2019(COVID-19).However,the high prevalence of preexisting anti-vector immunity compromises the immunogenicity of Ad5-based vaccines.Thus,there is a substantial unmet need to minimize preexisting immunity while improving the insert-induced immunity of Ad5 vectors.Herein,we address this need by utilizing biocompatible nanoparticles to modulate Ad5–host interactions.We show that positively charged human serum albumin nanoparticles((+)HSAnp),which are capable of forming a complex with Ad5,significantly increase the transgene expression of Ad5 in both coxsackievirus–adenovirus receptor-positive and-negative cells.Furthermore,in charge-and dose-dependent manners,Ad5/(+)HSAnp complexes achieve robust(up to227-fold higher)and long-term(up to 60 days)transgene expression in the lungs of mice following intranasal instillation.Importantly,in the presence of preexisting anti-Ad5 immunity,complexed Ad5-based Ebola and COVID-19 vaccines significantly enhance antigen-specific humoral response and mucosal immunity.These findings suggest that viral aggregation and charge modification could be leveraged to engineer enhanced viral vectors for vaccines and gene therapies.
基金supported by the National Key Research and Development Program of China,(Grant No.2019YFC1509702).
文摘The existence of defects in a rock mass is a vital factor complicating the mechanical response of the rock mass under stress.The characteristics of defects control the rock mass’s mechanical behaviors.This report reviews the experimental studies on the influence of simulating the internal defects of rock mass’s mechanical properties.The effects of preexisting defects(shape,size,number,angle,and other factors)on the mechanical properties and failure modes of the rock are investigated from the perspectives of rock failure and fracture mechanics.The fracture propagation mechanisms of different defective rock masses are analyzed by studying the stress state of different defective rock masses under uniaxial compression.After the defective rock samples with varying inclination angles are destroyed,the relationship among the compressive strength,the fracture propagation,and the failure characteristics is explored.The primary findings are as follows.The increase in the size and number of defects rapidly damages the mechanical properties of the rock and intensifies defect penetration and expansion.The rock mechanics characteristics of fissured rocks with different inclination angles show two primary variations:one is a continuous increase,and the other is a decrease followed by an increase.This result is strongly related to the failure pattern of rocks with preexisting fissures.This investigation is crucial for further studying the failure modes of complex defective rock masses and the geotechnical engineering related to defective rocks.
文摘The region between the preexisting and nascentmembranes of a cleaving Rana egg is a dense protrusionregion of nearly 40μm wide at 180°stage.Later,thisregion differentiate,into an upper part,a strip withlong, branched and randomly distributed protrusionswhich are derived largely from the preexistingmembrane,and a lower part,a band with microvilli.During 4-and 8-cel1 stages,the strip is almost vanishedand microvilli in the band is shortened.The nascentmembrane is smooth at the 180°stage,then a rough areaappears below the smooth region and quickly expands.Wheat germ agglutinin which can bind to preexistingmembrane interrupts the development of the regionbetween the preexisting and nascent membranes.Detergent,Brij,having the property to increase the areaof nascent membrane,does not interrupt the developmentof the region between the preexisting and nascentmembranes.
基金This study has been partially funded by the National Key Research and Development Program of China,China(Grant No.2020YFA0711800)the National Natural Science Foundation of China(Grant Nos.51734009,51979272,and 52179118)Natural Science Foundation of Jiangsu Province,China(No.BK20211584).These supports are gratefully acknowledged.
文摘Four types of granite specimens were prepared and treated by chemical corrosion for 5 and 30 days,which were then used to carry out triaxial compression tests under different confining pressuresσ_(3).Type A is the intact sample with no preexisting flaws.Types B and C are the samples containing two relatively low-dip flaws and two relatively high-dip flaws,respectively.Type D is the sample including both relatively low-dip and relatively high-dip flaws.The influences of pH value of chemical solutions,flaw distribution,corrosion time andσ_(3) on triaxial stress-strain curves and ultimate failure modes are analyzed and discussed.The results show that the pH value of the chemical solution,corrosion time and the arrangement of preexisting flaws play crucial roles in the cracking behaviors of granite specimens.Type A specimens have the largest peak axial deviatoric stress,followed by Type C,Type D,and Type B specimens,respectively.It is because the decrease in the inclination of preexisting flaws induces the weakening effect due to the decrease in the shadow area along the compaction direction.Under aσ_(3) of 5 MPa,the peak axial deviatoric stress drops by approximately 40.89%,29.08%,4.08%,and 23.53%for pH=2,4,7,and 12,respectively.For intact granite(Type A)specimens,the ultimate failure mode displays a typical shear mode.The connection of two secondary cracks initiated at the tips of preexisting cracks is always the ultimate failure and crack coalescence mode for Type B specimens.The ultimate failure and crack coalescence mode of Types C and D specimens are significantly affected by pH value of the chemical solution,corrosion time andσ_(3),which is different from those of Types A and B specimens due to the differences in flow distributions.
基金the financial support from the Science and Technology Department of Sichuan Province(Nos.2021YFH0048 and 2021YFH0118)a project funded by the China Postdoctoral Science Foundation(No.2020M683253).
文摘A validated particle flow code(PFC^(2D))-based model was developed to investigate the indirect tensile mechanical behavior of shale containing two central parallel cracks under Brazilian splitting test conditions.The results show that preexisting cracks have a significant and insignificant influence on the tensile strength of shale under LPL and LVL conditions,respectively.When L≥10 mm,changing the L and H values has little effect on the tensile strength of shale.However,the inclusion of preexisting cracks have a positive effect on reducing the anisotropy of the shale specimens,and in the case of an L/D ratio of 0.3,the shale anisotropy is the lowest.Four failure modes were formed at differentβandθvalues under LPL conditions.In the case ofβ≥60°,the failure mode is mainly affected byβ,and whenβ≤45°,the failure mode is more complicated than in the case ofβ≥60°.Only three major failure modes were observed under LVL conditions;in the case of 45°≤β≤75°andθ≤30°,the most complex failure mode occurred.
基金the National Science and Technology Major Project of China(No.2018ZX10302206-003)the Zhejiang Provincial Natural Science Foundation of China(No.LY16H160057)+1 种基金the Health Commission of Zhejiang Province(No.2016KYA162)the Zhejiang Provincial Science and Technology Project of Traditional Chinese Medicine of China(No.2015ZA026)。
文摘Although the coronavirus disease 2019(COVID-19)epidemic is still ongoing,vaccination rates are rising slowly and related treatments and drugs are being developed.At the same time,there is increasing evidence of preexisting immunity against severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)in humans,mainly consisting of preexisting antibodies and immune cells(including T cells and B cells).The presence of these antibodies is mainly due to the seasonal prevalence of four common coronavirus types,especially OC43 and HKU1.The accumulated relevant evidence has suggested that the target of antibodies is mainly the S2 subunit of S protein,followed by evolutionary conservative regions such as the nucleocapsid(N)protein.Additionally,preexisting memory T and B cells are also present in the population.Preexisting antibodies can help the body protect against SARS-CoV-2 infection,reduce the severity of COVID-19,and rapidly increase the immune response post-infection.These multiple effects can directly affect disease progression and even the likelihood of death in certain individuals.Besides the positive effects,preexisting immunity may also have negative consequences,such as antibody-dependent enhancement(ADE)and original antigenic sin(OAS),the prevalence of which needs to be further established.In the future,more research should be focused on evaluating the role of preexisting immunity in COVID-19 outcomes,adopting appropriate policies and strategies for fighting the pandemic,and vaccine development that considers preexisting immunity.
基金National Natural Science Foundation of China(No.42007256 and 41672258)the Fundamental Research Funds for the Central Universities(B210201002)。
文摘Steps are distinctive features for estimating the movement of the upper and lower block of faults.However,studies about the influence of steps as a special type of discontinuity on cracking behaviors and strength of rock masses are limited.In this research,rock-like samples with steps and preexisting flaws were fabricated.Step height h and the inclination angle of gentle slope of the stepαwere set to different values.Direct shear tests were conducted on these samples under different normal stresses.The experimental results reveal that the inclination angle of the gentle slope of the stepα,step height h,and normal stress have an influence on the strength,crack initiation,and crack propagation of the samples.The experimental results show that crack behaviors and shear strength were affected by step inclination anglesαand step height h.As the normal stress increases,the improvement of the strength of samples with a large step height is larger than that of samples with a small step height,the improvement of the strength of samples withαof 10°is larger than that of samples withαof 0°and-10°.The discrete element method was used to simulate the shear test.Numerical results show five different types of displacement vectors,which can be used to determine whether the cracks are tensile cracks or shear cracks.The above conclusions can provide help for estimating mechanical properties and failure modes of rock masses with steps of different geometries.
基金Supported by the China National Science and Technology Major Project(2016ZX05026-003,2011ZX05025-003)Science and Technology Project of CNOOC Limited(YXKY-2012-SHENHAI-01)CNOOC-KJ 135 ZDXM 37 SZ 01 SHENHAI。
文摘Based on the new seismic and drilling data and the recent related research results,this paper systematically analyzes the diversity and complexity of evolution process of crustal lithosphere structure and basin structure in the Pearl River Mouth Basin on the northern margin of the South China Sea.Three types of detachment faults of different structural levels exist:crust-mantle detachment,inter-crust detachment and upper crust detachment.It is considered that different types of extensional detachment control different subbasin structures.Many fault depressions controlled by upper crust detachment faults have been found in the Zhu I Depression located in the proximal zone.These detachment faults are usually reformed by magma emplacement or controlled by preexisting faults.Baiyun-Liwan Sag located in the hyperextension area shows different characteristics of internal structure.The Baiyun main sag with relative weak magmatism transformation is a wide-deep fault depression,which is controlled by crust-mantle detachment system.Extensive magmatism occurred in the eastern and southwest fault steps of the Baiyun Sag after Middle Eocene,and the crust ductile extensional deformation resulted in wide-shallow fault depression controlled by the upper crust detachment fault.Based on the classical lithosphere extensional breaking and basin tectonic evolution in the Atlantic margin,it is believed that the magmatic activities and pre-existing structures in the Mesozoic subduction continental margin background are important controlling factors for the diversified continental margin faulted structures in the northern South China Sea.
基金a result of key scientific research project of China Seismological Bureau (95-04-08-02-02).
文摘Shallow seismic profiling in meizoseismal area of Xingtai earthquakes, phase division of Cenozoic movement of deep and shallow structures, analysis of characteristics of crustal and upper mantle structure, and comparative study on parameters of seismic sources indicate that the listric faults controlling the development of early Tertiary basin-range structure and eastward gently-dipping detachment below it in the Xingtai epicentral area are not related to the occurrence of Xingtai earthquakes. The Xingtai earthquake swarm is a product of three-dimensional fracture process in which the discontinuous "deep faults", separated by NW-trending faults or by transverse barriers, successively tore, fractured, and propagated upward and, hence, caused the stress between the adjacent deep faults to migrate and load under the action of latest tectonic stress field. The Xingtai seismogenic fault represents a " newly generated fault" resulted from the upward tearing and propagation of the preexisting crustal " deep fault".
