To reveal stress distribution and crack propagation of Brazilian discs under impact loads, dynamic tests were conducted with SHPB （split Hopkinson pressure bar） device. Stress states of specimens were monitored with...To reveal stress distribution and crack propagation of Brazilian discs under impact loads, dynamic tests were conducted with SHPB （split Hopkinson pressure bar） device. Stress states of specimens were monitored with strain gauges on specimen surface and SHPB bars. The failure process of specimen was recorded by ultra speed camera FASTCAM SAI.1 （675 000 fps）. Stress histories from strain gauges offer comprehensive information to evaluate the stress equilibrium of specimen in time and space. When a slowly rising load （with loading rates less than 1 200 N/s for d 50 mm bar） is applied, there is usually good stress equilibrium in specimen. The stress distribution after equilibrium is similar to its static counterpart. And the first crack initiates at the disc center and propagates along the load direction. But with the front of incident wave becoming steep, it is hard for specimens to get to stress equilibrium. The first crack may appear anywhere on the specimen together with multiple randomly distributed secondary cracks. For a valid dynamic Brazil test with stress equilibrium, the specimen will break into two halves neatly. While for tests with stress disequilibrium, missing strap may be found when broken halves of specimens are put together. For those specimens broken up neatly at center but having missing wedges at the loading areas, it is usually subjected to local buckling from SHPB bars.展开更多
Background:Pectin is a key substance involved in cell wall development,and the galacturonosyltransferases(GAUTs)gene family is a critical participant in the pectin synthesis pathway.Systematic and comprehensive resear...Background:Pectin is a key substance involved in cell wall development,and the galacturonosyltransferases(GAUTs)gene family is a critical participant in the pectin synthesis pathway.Systematic and comprehensive research on GAUTs has not been performed in cotton.Analysis of the evolution and expression patterns of the GAUT gene family in different cotton species is needed to in crease kno wledge of the functi on of pectin in cotto n fiber development.Results:In this study,we have identified 131 GAUT genes in the genomes of four Gossypium species(G.raimondii,G barbadense,G.hirsutum,and G.arboreum),and classified them as GAUT-A,GAUT-B and GAUT-C,which coding probable galacturonosyltransferases.Among them,the GAUT genes encode proteins GAUT1 to GAUT15.All GAUT proteins except for GAUT7 contai n a con served glycosyl transferase family 8 domain(H-DN-A-SW-S-V-H-T-F).The conserved sequence of GAUT7 is PLN(phospholamban)02769 domain.According to c/s-elemet analysis,GAUT genes transcript levels may be regulated by horm ones such as JA,GA,SA,ABA,Me-JA,and IA A.The evoluti on and transcription patterns of the GAUT gene family in different cotton species and the transcript levels in upland cotton lines with different fiber st「ength were analyzed.Peak transcript level of GhGAUT genes have been observed before 15 DPA.In the six materials with high fiber strength,the transcription of GhGAUT genes were concentrated from 10 to 15 DPA;while the highest transcript levels in low fiber st「ength materials were detected between 5 and 10 DPA.These results lays the foundation for future research on gene function during cotton fiber development.Conclusions:The GAUT gene family may affect cotton fiber development,including fiber elongation and fiber thickening.In the low strength fiber lines,GAUTs mainly participate in fiber elongation,whereas their major effect on cotton with high strength fiber is related to both elongation and thickening.展开更多
基金Projects(50904079, 51274254, 50934006) supported by the National Natural Science Foundation of ChinaProject(2010CB732004) supported by the National Basic Research Program of ChinaProject(NCET-11-0528) supported by Program for New Century Excellent Talents in University of China
文摘To reveal stress distribution and crack propagation of Brazilian discs under impact loads, dynamic tests were conducted with SHPB （split Hopkinson pressure bar） device. Stress states of specimens were monitored with strain gauges on specimen surface and SHPB bars. The failure process of specimen was recorded by ultra speed camera FASTCAM SAI.1 （675 000 fps）. Stress histories from strain gauges offer comprehensive information to evaluate the stress equilibrium of specimen in time and space. When a slowly rising load （with loading rates less than 1 200 N/s for d 50 mm bar） is applied, there is usually good stress equilibrium in specimen. The stress distribution after equilibrium is similar to its static counterpart. And the first crack initiates at the disc center and propagates along the load direction. But with the front of incident wave becoming steep, it is hard for specimens to get to stress equilibrium. The first crack may appear anywhere on the specimen together with multiple randomly distributed secondary cracks. For a valid dynamic Brazil test with stress equilibrium, the specimen will break into two halves neatly. While for tests with stress disequilibrium, missing strap may be found when broken halves of specimens are put together. For those specimens broken up neatly at center but having missing wedges at the loading areas, it is usually subjected to local buckling from SHPB bars.
基金the Major Research Plan of National Natural Science Foundation of China(NO.31690093)the National Agricultural Science and Technology Innovation project for CAAS(CAAS-ASTIP-2016-ICR)the Central Level of the Scientific Research Institutes for Basic R&D Special Fund Business(Y2017PT51)。
文摘Background:Pectin is a key substance involved in cell wall development,and the galacturonosyltransferases(GAUTs)gene family is a critical participant in the pectin synthesis pathway.Systematic and comprehensive research on GAUTs has not been performed in cotton.Analysis of the evolution and expression patterns of the GAUT gene family in different cotton species is needed to in crease kno wledge of the functi on of pectin in cotto n fiber development.Results:In this study,we have identified 131 GAUT genes in the genomes of four Gossypium species(G.raimondii,G barbadense,G.hirsutum,and G.arboreum),and classified them as GAUT-A,GAUT-B and GAUT-C,which coding probable galacturonosyltransferases.Among them,the GAUT genes encode proteins GAUT1 to GAUT15.All GAUT proteins except for GAUT7 contai n a con served glycosyl transferase family 8 domain(H-DN-A-SW-S-V-H-T-F).The conserved sequence of GAUT7 is PLN(phospholamban)02769 domain.According to c/s-elemet analysis,GAUT genes transcript levels may be regulated by horm ones such as JA,GA,SA,ABA,Me-JA,and IA A.The evoluti on and transcription patterns of the GAUT gene family in different cotton species and the transcript levels in upland cotton lines with different fiber st「ength were analyzed.Peak transcript level of GhGAUT genes have been observed before 15 DPA.In the six materials with high fiber strength,the transcription of GhGAUT genes were concentrated from 10 to 15 DPA;while the highest transcript levels in low fiber st「ength materials were detected between 5 and 10 DPA.These results lays the foundation for future research on gene function during cotton fiber development.Conclusions:The GAUT gene family may affect cotton fiber development,including fiber elongation and fiber thickening.In the low strength fiber lines,GAUTs mainly participate in fiber elongation,whereas their major effect on cotton with high strength fiber is related to both elongation and thickening.
