Case histories have shown that the liquefaction-induced soil lateral spreading is one of the main causes of damage to pile foundations subjected to seismic loading. Post-liquefaction soil behaves similarly to a viscou...Case histories have shown that the liquefaction-induced soil lateral spreading is one of the main causes of damage to pile foundations subjected to seismic loading. Post-liquefaction soil behaves similarly to a viscous fluid. This study investigated the effect of soil lateral spreading on a single pile based on fluid mechanics in which the liquefied soils were treated as Newtonian fluids. A numerical simulation on a single pile embedded in a fully saturated sandy foundation was conducted and compared with shake table tests. The lateral flow effect and the effect of shear strain rate were discussed. After liquefaction, the acceleration of the foundation shows that there are no obvious spikes and finally reaches a stable state. The presented method can predict the pile response better than p-y curve method. A parametric study was performed to explore the effect of several influence factors on pile behaviors. The results show that the pile head displacement decreases and the maximum bending moment at pile bottom increases with the increase of bending stiffness. With the same pile bending stiffness, the displacement and bending moment of pile increase with the increase of soil viscosity and acceleration amplitude.展开更多
Sex determination in plants gives rise to unisexual flowers that facilitate outcrossing and enhance genetic diversity. In cucumber and melon, ethylene promotes carpel development and arrests sta- men development. Five...Sex determination in plants gives rise to unisexual flowers that facilitate outcrossing and enhance genetic diversity. In cucumber and melon, ethylene promotes carpel development and arrests sta- men development. Five sex-determination genes have been identified, including four encoding 1-aminocyclopropane-l-carboxylate （ACC） synthase that catalyzes the rate-limiting step in ethylene biosynthesis, and a transcription factor gene CmWIP1 that corresponds to the Mendelian locus gynoecious in melon and is a negative regulator of femaleness. ACC oxidase （ACO） converts ACC into ethylene; how- ever, it remains elusive which ACO gene in the cucumber genome is critical for sex determination and how CmWIP1 represses development of female flowers. In this study, we discovered that mutation in an ACO gene, CsAC02, confers androecy in cucumber that bears only male flowers. The mutation disrupts the enzymatic activity of CsAC02, resulting in 50% less ethylene emission from shoot tips. CsAC02 was ex- pressed in the carpel primordia and its expression overlapped with that of CsACS11 in female flowers at key stages for sex determination, presumably providing sufficient ethylene required for proper CsACS2 expression. CmAC03, the ortholog of CsACO2, showed a similar expression pattern in the carpel region, suggesting a conserved function of CsACO2/CmACO3. We demonstrated that CsWlP1, the ortholog of CmWlP1, could directly bind the promoter of CsAC02 and repress its expression. Taken together, we propose a presumably conserved regulatory module consisting of WlP1 transcription factor and ACO controls unisexual flower development in cucumber and melon.展开更多
Summary We isolated a mutant showing perturbations in the development of male and female floral organs and fruits. Analysis of the single nucleotide polyTnorphisms from bulked F2 pools identified the causative variant...Summary We isolated a mutant showing perturbations in the development of male and female floral organs and fruits. Analysis of the single nucleotide polyTnorphisms from bulked F2 pools identified the causative variant occurring in Csa4G126690. Csa4G126690 shows high homol- ogy to Arobidopsis 5EPALLATA2 （SEP2） thus being desig- nated CsSEP2. The causative variant was located on the splicing site of CsSEP2, resulting in the skipping of exon 6 and abolishment of the transcriptional activity. Our data suggest that CsSEP2 is involved in the floral organ and fruits development by conferring transcriptional activity.展开更多
Dear Editor,Gynoecism has been extensively exploited in cucumber breeding. The utilization of a gynoecious line permits earlier pro- duction of hybrids, higher yield, and more concentrated fruit set. In addition, the ...Dear Editor,Gynoecism has been extensively exploited in cucumber breeding. The utilization of a gynoecious line permits earlier pro- duction of hybrids, higher yield, and more concentrated fruit set. In addition, the utilization of a gynoecious line eliminates the need for hand emasculation and reduces the labor cost of crossing （Robinson, 2000）. Therefore, the development of gynoeoious inbred lines is instrumental for cucumber breeding. Gynoecious inbreds can be produced by selection from crosses of monoecious inbreds, or can arise spontaneously from natural variation. However, both methods have disadvantages. For instance, the time-consuming and laborious process of crossing can also lead to the introduction of undesirable traits,展开更多
文摘Case histories have shown that the liquefaction-induced soil lateral spreading is one of the main causes of damage to pile foundations subjected to seismic loading. Post-liquefaction soil behaves similarly to a viscous fluid. This study investigated the effect of soil lateral spreading on a single pile based on fluid mechanics in which the liquefied soils were treated as Newtonian fluids. A numerical simulation on a single pile embedded in a fully saturated sandy foundation was conducted and compared with shake table tests. The lateral flow effect and the effect of shear strain rate were discussed. After liquefaction, the acceleration of the foundation shows that there are no obvious spikes and finally reaches a stable state. The presented method can predict the pile response better than p-y curve method. A parametric study was performed to explore the effect of several influence factors on pile behaviors. The results show that the pile head displacement decreases and the maximum bending moment at pile bottom increases with the increase of bending stiffness. With the same pile bending stiffness, the displacement and bending moment of pile increase with the increase of soil viscosity and acceleration amplitude.
基金supported by the National Natural Science Foundation of China (No. 51676007, No. 51376001, No. 51420105008)supported by the China Scholarship council (CSC)
文摘Sex determination in plants gives rise to unisexual flowers that facilitate outcrossing and enhance genetic diversity. In cucumber and melon, ethylene promotes carpel development and arrests sta- men development. Five sex-determination genes have been identified, including four encoding 1-aminocyclopropane-l-carboxylate （ACC） synthase that catalyzes the rate-limiting step in ethylene biosynthesis, and a transcription factor gene CmWIP1 that corresponds to the Mendelian locus gynoecious in melon and is a negative regulator of femaleness. ACC oxidase （ACO） converts ACC into ethylene; how- ever, it remains elusive which ACO gene in the cucumber genome is critical for sex determination and how CmWIP1 represses development of female flowers. In this study, we discovered that mutation in an ACO gene, CsAC02, confers androecy in cucumber that bears only male flowers. The mutation disrupts the enzymatic activity of CsAC02, resulting in 50% less ethylene emission from shoot tips. CsAC02 was ex- pressed in the carpel primordia and its expression overlapped with that of CsACS11 in female flowers at key stages for sex determination, presumably providing sufficient ethylene required for proper CsACS2 expression. CmAC03, the ortholog of CsACO2, showed a similar expression pattern in the carpel region, suggesting a conserved function of CsACO2/CmACO3. We demonstrated that CsWlP1, the ortholog of CmWlP1, could directly bind the promoter of CsAC02 and repress its expression. Taken together, we propose a presumably conserved regulatory module consisting of WlP1 transcription factor and ACO controls unisexual flower development in cucumber and melon.
基金supported by grants from the National Natural Science Foundation of China (31225025)the National Program on Key Basic Research Projects in China (2012CB113900)the China Postdoctoral Science Foundation (2015M581217)
文摘Summary We isolated a mutant showing perturbations in the development of male and female floral organs and fruits. Analysis of the single nucleotide polyTnorphisms from bulked F2 pools identified the causative variant occurring in Csa4G126690. Csa4G126690 shows high homol- ogy to Arobidopsis 5EPALLATA2 （SEP2） thus being desig- nated CsSEP2. The causative variant was located on the splicing site of CsSEP2, resulting in the skipping of exon 6 and abolishment of the transcriptional activity. Our data suggest that CsSEP2 is involved in the floral organ and fruits development by conferring transcriptional activity.
文摘Dear Editor,Gynoecism has been extensively exploited in cucumber breeding. The utilization of a gynoecious line permits earlier pro- duction of hybrids, higher yield, and more concentrated fruit set. In addition, the utilization of a gynoecious line eliminates the need for hand emasculation and reduces the labor cost of crossing （Robinson, 2000）. Therefore, the development of gynoeoious inbred lines is instrumental for cucumber breeding. Gynoecious inbreds can be produced by selection from crosses of monoecious inbreds, or can arise spontaneously from natural variation. However, both methods have disadvantages. For instance, the time-consuming and laborious process of crossing can also lead to the introduction of undesirable traits,
