Thin-walled structures are commonly utilized in aerospace and aircraft structures,which are prone to buckling under axial compression and extremely sensitive to geometric imperfections.After decades of efforts,it stil...Thin-walled structures are commonly utilized in aerospace and aircraft structures,which are prone to buckling under axial compression and extremely sensitive to geometric imperfections.After decades of efforts,it still remains a challenging issue to accurately predict the lower-bound buckling load due to the impact of geometric imperfections.Up to now,the lower-bound curve in NASA SP-8007 is still widely used as the design criterion of aerospace thin-walled structures,and this series of knockdown factors(KDF)has been proven to be overly conservative with the significant promotion of the manufacturing process.In recent years,several new numerical and experimental methods for determining KDF have been established,which are systematically reviewed in this paper.The Worst Multiple Perturbation Load Approach(WMPLA)is one of the most representative methods to reduce the conservatism of traditional methods in a rational manner.Based on an extensive collection of test data from 1990 to 2020,a new lower-bound curve is approximated to produce a series of improved KDFs.It is evident that these new KDFs have an overall improvement of 0.1-0.3 compared with NASA SP-8007,and the KDF predicted by the WMPLA is very close to the front of the new curve.This may provide some insight into future design guidelines of axially compressed cylindrical shells,which is promising for the lightweight design of large-diameter aerospace structures.展开更多
Pitx3 is strongly associated with the phenotype, differentiation, and survival of dopaminergic neurons. The relationship between Pitx3 and glial cell line-derived neurotrophic factor（GDNF） in dopaminergic neurons re...Pitx3 is strongly associated with the phenotype, differentiation, and survival of dopaminergic neurons. The relationship between Pitx3 and glial cell line-derived neurotrophic factor（GDNF） in dopaminergic neurons remains poorly understood. The present investigation sought to construct and screen a lentivirus expression plasmid carrying a rat Pitx3 short hairpin（sh）RNA and to assess the impact of Pitx3 gene knockdown on GDNF transcriptional activity in MES23.5 dopaminergic neurons. Three pairs of interference sequences were designed and separately ligated into GV102 expression vectors. These recombinant plasmids were transfected into MES23.5 cells and western blot assays were performed to detect Pitx3 protein expression. Finally, the most effective Pitx3 sh RNA and a dual-luciferase reporter gene plasmid carrying the GDNF promoter region（GDNF-luciferase） were cotransfected into MES23.5 cells. Sequencing showed that the synthesized sequences were identical to the three Pitx3 interference sequences. Inverted fluorescence microscopy revealed that the lentivirus expression plasmids carrying Pitx3-sh RNA had 40-50% transfection efficiency. Western blot assay confirmed that the corresponding Pitx3 of the third knockdown sequence had the lowest expression level. Dual-luciferase reporter gene results showed that the GDNF transcriptional activity in dopaminergic cells cotransfected with both plasmids was decreased compared with those transfected with GDNF-luciferase alone. Together, the results showed that the designed Pitx3-sh RNA interference sequence decreased Pitx3 protein expression, which decreased GDNF transcriptional activity.展开更多
Axially loaded tubular structures are known to be highly sensitive to initial geometric imperfections,which can significantly reduce their design bearing capacity.To address this issue,this study explores the potentia...Axially loaded tubular structures are known to be highly sensitive to initial geometric imperfections,which can significantly reduce their design bearing capacity.To address this issue,this study explores the potential of an origami-inspired design for tubular structures to achieve a lower sensitivity to imperfections.The study considers various designs,including diamond-shaped,pyramid-shaped,new Kresling,and pre-embedded rhombic origami tubes,and employs knockdown factors(KDFs)to illustrate the reduction of the design bearing capacity of these structures with initial geometric imperfections for safety purposes.Finite element analysis shows that some of the origami tubes have superior design bearing capacity,mass efficiency,and KDFs when compared to standard circular tubes.Among the origami tubes considered,the rhombic tube demonstrates the best performance and is further studied through parametric analyses of geometric design,aspect ratio,and wall thickness to achieve additional performance enhancements.Furthermore,the superior performance of the rhombic tube is evaluated and verified for various loading scenarios,including eccentric compression and compression-torsion combination.The findings of this study provide a promising approach to designing and fabricating imperfection-insensitive tubes using advanced processing technologies such as additive manufacturing.This work can potentially lead to the development of innovative tubular structures with enhanced safety and reliability in various engineering applications.展开更多
目的构建KLF2过表达BGC823和KLF2敲减MGC803胃癌稳转细胞株。方法克隆人源KLF2基因,连接到Age I/Age I酶切后GV358载体上,构建GV358-KLF2重组质粒,转染293T细胞,包装慢病毒;构建KLF2shRNA,连接到Bam HI和EcoRI双酶切后的PHBLV-U6-ZSGree...目的构建KLF2过表达BGC823和KLF2敲减MGC803胃癌稳转细胞株。方法克隆人源KLF2基因,连接到Age I/Age I酶切后GV358载体上,构建GV358-KLF2重组质粒,转染293T细胞,包装慢病毒;构建KLF2shRNA,连接到Bam HI和EcoRI双酶切后的PHBLV-U6-ZSGreen-Puro载体上,经鉴定后转染293T细胞。采用RT-PCR及Western印迹法检测稳转细胞株中KLF2的表达。结果利用慢病毒介导,重组质粒G V358-K L F2和K L F2-shRN A转导入B G C823细胞、M G C803细胞并稳定表达。RT-PC R和W estern印迹法结果均显示过表达稳转株KLF2表达量明显升高(P<0.05),敲减稳转株KLF2表达量明显下降(P<0.05)。结论成功构建了K L F2过表达B G C823细胞株和K L F2敲减M G C803细胞株,为后续K L F2功能实验奠定了基础。展开更多
基金the National Natural Science Foundation of China(Grant Nos.U21A20429,11772078,and 11825202)the National Defense Basic Research Program(Grant No.JCKY2020110).
文摘Thin-walled structures are commonly utilized in aerospace and aircraft structures,which are prone to buckling under axial compression and extremely sensitive to geometric imperfections.After decades of efforts,it still remains a challenging issue to accurately predict the lower-bound buckling load due to the impact of geometric imperfections.Up to now,the lower-bound curve in NASA SP-8007 is still widely used as the design criterion of aerospace thin-walled structures,and this series of knockdown factors(KDF)has been proven to be overly conservative with the significant promotion of the manufacturing process.In recent years,several new numerical and experimental methods for determining KDF have been established,which are systematically reviewed in this paper.The Worst Multiple Perturbation Load Approach(WMPLA)is one of the most representative methods to reduce the conservatism of traditional methods in a rational manner.Based on an extensive collection of test data from 1990 to 2020,a new lower-bound curve is approximated to produce a series of improved KDFs.It is evident that these new KDFs have an overall improvement of 0.1-0.3 compared with NASA SP-8007,and the KDF predicted by the WMPLA is very close to the front of the new curve.This may provide some insight into future design guidelines of axially compressed cylindrical shells,which is promising for the lightweight design of large-diameter aerospace structures.
基金supported by the National Natural Science Foundation of China,No.81372698
文摘Pitx3 is strongly associated with the phenotype, differentiation, and survival of dopaminergic neurons. The relationship between Pitx3 and glial cell line-derived neurotrophic factor（GDNF） in dopaminergic neurons remains poorly understood. The present investigation sought to construct and screen a lentivirus expression plasmid carrying a rat Pitx3 short hairpin（sh）RNA and to assess the impact of Pitx3 gene knockdown on GDNF transcriptional activity in MES23.5 dopaminergic neurons. Three pairs of interference sequences were designed and separately ligated into GV102 expression vectors. These recombinant plasmids were transfected into MES23.5 cells and western blot assays were performed to detect Pitx3 protein expression. Finally, the most effective Pitx3 sh RNA and a dual-luciferase reporter gene plasmid carrying the GDNF promoter region（GDNF-luciferase） were cotransfected into MES23.5 cells. Sequencing showed that the synthesized sequences were identical to the three Pitx3 interference sequences. Inverted fluorescence microscopy revealed that the lentivirus expression plasmids carrying Pitx3-sh RNA had 40-50% transfection efficiency. Western blot assay confirmed that the corresponding Pitx3 of the third knockdown sequence had the lowest expression level. Dual-luciferase reporter gene results showed that the GDNF transcriptional activity in dopaminergic cells cotransfected with both plasmids was decreased compared with those transfected with GDNF-luciferase alone. Together, the results showed that the designed Pitx3-sh RNA interference sequence decreased Pitx3 protein expression, which decreased GDNF transcriptional activity.
基金supported by the National Natural Science Foundation of China(Grant No.U1937202)Key Industrial Technology Research&Development Cooperation Projects of Jiangsu Province(BZ2021036)Basic Research Projects on Free Exploration of Funds for Local Scientific and Technological Development Guided by the Central Government(2021Szvup027).
文摘Axially loaded tubular structures are known to be highly sensitive to initial geometric imperfections,which can significantly reduce their design bearing capacity.To address this issue,this study explores the potential of an origami-inspired design for tubular structures to achieve a lower sensitivity to imperfections.The study considers various designs,including diamond-shaped,pyramid-shaped,new Kresling,and pre-embedded rhombic origami tubes,and employs knockdown factors(KDFs)to illustrate the reduction of the design bearing capacity of these structures with initial geometric imperfections for safety purposes.Finite element analysis shows that some of the origami tubes have superior design bearing capacity,mass efficiency,and KDFs when compared to standard circular tubes.Among the origami tubes considered,the rhombic tube demonstrates the best performance and is further studied through parametric analyses of geometric design,aspect ratio,and wall thickness to achieve additional performance enhancements.Furthermore,the superior performance of the rhombic tube is evaluated and verified for various loading scenarios,including eccentric compression and compression-torsion combination.The findings of this study provide a promising approach to designing and fabricating imperfection-insensitive tubes using advanced processing technologies such as additive manufacturing.This work can potentially lead to the development of innovative tubular structures with enhanced safety and reliability in various engineering applications.
文摘目的构建KLF2过表达BGC823和KLF2敲减MGC803胃癌稳转细胞株。方法克隆人源KLF2基因,连接到Age I/Age I酶切后GV358载体上,构建GV358-KLF2重组质粒,转染293T细胞,包装慢病毒;构建KLF2shRNA,连接到Bam HI和EcoRI双酶切后的PHBLV-U6-ZSGreen-Puro载体上,经鉴定后转染293T细胞。采用RT-PCR及Western印迹法检测稳转细胞株中KLF2的表达。结果利用慢病毒介导,重组质粒G V358-K L F2和K L F2-shRN A转导入B G C823细胞、M G C803细胞并稳定表达。RT-PC R和W estern印迹法结果均显示过表达稳转株KLF2表达量明显升高(P<0.05),敲减稳转株KLF2表达量明显下降(P<0.05)。结论成功构建了K L F2过表达B G C823细胞株和K L F2敲减M G C803细胞株,为后续K L F2功能实验奠定了基础。
