Effective reduction in chimeric mutants of poplar trees produced by CRISPR/Cas9 through a second round of shoot regeneration

Liping Ding,Yajuan Chen,Yan Ma,Hongzhi Wang,Jianhua Wei 한국식물생명공학회 2020 Plant biotechnology reports Vol.14 No.5

The clustered regulatory interspaced short palindromic repeat/CRISPR-associated protein 9 (CRISPR/Cas9) system has been applied to edit the genomes of quite a few plant species, including perennial woody poplar trees. However, chimeras often exist in primary transgenic plants. For perennial woody trees such as poplar trees, it is difcult to obtain homozygous mutants by self-pollination for due to their long vegetative life and low-seed setting rates. In this study, we report an efec�tive approach to reduce the frequency of chimeric mutants of poplar trees by CRISPR/Cas9 with a second round of shoot regeneration using leaves as the explants. PdbPDS1 was used as the target gene, and only one homozygous PdbPDS1 mutant was obtained from 15 primary transgenic plantlets, which was verifed by both the phenotype and the DNA sequence of the PCR product. This indicates that the majority of primary transgenic plantlets in the T0 generation were chimeras. After the second round of shoot regeneration of the chimeric mutants generated by CRISPR/Cas9, approximately 27.0% or 19.1% of the regenerated shoots were homozygous mutants with or without kanamycin selection, respectively. The results showed that a second regeneration could produce homozygous mutant shoots at a high frequency and that kanamycin selection could increase the frequency of homozygous mutant shoots.

Composite action of concrete-filled double circular steel tubular stub columns

Liping Wang,Xing-xing Cao,Fa-Xing Ding,Liang Luo,Yi Sun,Xue-mei Liu,Hui-lin Su 국제구조공학회 2018 Steel and Composite Structures, An International J Vol.29 No.1

This paper presents a combined numerical, experimental, and theoretical study on the behavior of the concrete-filled double circular steel tubular (CFDT) stub columns under axial compressive loading. Four groups of stub column specimens were tested in this study to find out the effects of the concrete strength, steel ratio and diameter ratio on the mechanical behavior of CFDT stub columns. Nonlinear finite element (FE) models were also established to study the stresses of different components in the CFDT stub columns. The change of axial and transverse stresses in the internal and external steel tubes, as well as the change of axial stress in the concrete sandwich and concrete core, respectively, was thoroughly investigated for different CFDT stub columns with the same steel ratio. The influence of inner-to-outer diameter ratio and steel ratio on the ultimate bearing capacity of CFDT stub columns was identified, and a reasonable section configuration with proper inner-to-outer diameter ratio and steel ratio was proposed. Furthermore, a practical formula for predicting the ultimate bearing capacity was proposed based on the ultimate equilibrium principle. The predicted results showed satisfactory agreement with both experimental and numerical results, indicating that the proposed formula is applicable for design purposes.

The smallest triangular cover for triangles ofdiameter one

Liping Yuan,Ren Ding 한국전산응용수학회 2005 Journal of applied mathematics & informatics Vol.17 No.1-2

English Language and Linguistics 20, 203-222. This paper tries to provide computational algorithms for multiple wh-movements in English. Multiple wh-movements have been one of the interesting topics in syntactic theories, and they can also be handled in Chomsky's Minimalist syntax. For computational implementations, this paper modifies Stabler's Computational Minimalism, and develops a Revised Computational Minimalism system (RCM). In this RCM system, Chomsky's Probe-Goal relations are applied and wh-movements are computationally implemented with wh-feature instantiation and its matching processes. In order to handle multiple features, we will adopt Chomsky's local merge, and multiple wh-movements will be implemented by multiple feature matching. In sum, this paper develops the algorithms by which we can computationally implement multiple wh-movements in Minimalist syntax.

Point transversals to translates of a trapezoid

Liping Yuan,Ren Ding 한국전산응용수학회 2004 Journal of applied mathematics & informatics Vol.15 No.-

An m-transversal to a family of convex sets in the plane isan m-point set which intersects every members of the family. One ofGr¨ubaum’s conjectures says that a planar family of translates of a con-vex compact set has a 3-transversal provided that any two of its membersintersect. Recently the conjecture has been proved armatively (see [4]).In the present paper we provide a dierent and straightforward proof forthe conjecture for the family of translates of a closed trapezoid in the planeand give several concrete 3-transversals.

THE SMALLEST TRIANGULAR COVER FOR TRIANGLES OF DIAMETER ONE

YUAN, LIPING,DING, REN 한국전산응용수학회 2005 Journal of applied mathematics & informatics Vol.17 No.1

A convex region covers a family of curves if it contains a congruent copy of each curve in the family, and a 'worm problem' for that family is to find the convex region of smallest area. In this paper, we find the smallest triangular cover of any prescribed shape for the family S of all triangles of diameter 1.

Behavior of circular thin-walled steel tube confined concrete stub columns

Fa-Xing Ding,Liu Tan,Xuemei Liu,Liping Wang 국제구조공학회 2017 Steel and Composite Structures, An International J Vol.23 No.2

This paper presents a combined numerical and theoretical study on the composite action between steel and concrete of circular steel tube confined concrete (STCC) stub columns under axial compressive loading with a full theoretical elasto-plastic model and finite element (FE) model in comparison with experimental results. Based on continuum mechanics, the elasto-plastic model for STCC stub columns was established and the analysis was realized by a FORTRAN program and the three dimensional FE model was developed using ABAQUS. The steel ratio of the circular STCC columns were defined in range of 0.5% to 2% to analyze the composite action between steel tube and concrete, and make a further study on the advantages of the circular STCC columns. By comparing the results using the elasto-plastic methods with the parametric analysis result of FE model, the appropriate friction coefficient between the steel tube and core concrete was defined as 0.4 to 0.6. Based on ultimate balance theory, the formula of ultimate load capacity applying to the circular STCC stub columns was developed.

Mechanical behavior of outer square inner circular concrete-filled dual steel tubular stub columns

Fa-Xing Ding,Wenjun Wang,Xue-mei Liu,Liping Wang,Yi Sun 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.38 No.3

The mechanical behavior of the outer square inner circular concrete-filled dual steel tubular (SCCFT) stub columns under axial compression is investigated by means of experimental research, numerical analysis and theoretical investigation. Parameters such as diameter ratio, concrete strength and steel ratio were discussed to identify their influence on the mechanical properties of SCCFT short columns on the basis of the experimental investigation of seven SCCFT short columns. By establishing a finite element model, nonlinear analysis was performed to discuss the longitudinal and transverse stress of the dual steel tubes. The longitudinal stress characteristics of the core and sandwich concrete were also analyzed. Furthermore, the failure sequence was illustrated and the reasonable cross-section composition of SCCFT stub column was proposed. A formula to predict the axial load capacity of SCCFT stub column was advanced and verified by the results from experiment and the finite element.

Confinement coefficient of concrete-filled square stainless steel tubular stub columns

Fa-Xing Ding,Yi-xiang Yin,Liping Wang,Yujie Yu,Liang Luo,Zhi-wu Yu 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.30 No.4

The objective of this paper is to investigate the confinement coefficient of concrete-filled square stainless steel tubular (CFSSST) stub columns under axial loading. A fine finite 3D solid element model was established, which utilized a constitutive model of stainless steel considering the strain-hardening characteristics and a triaxial plastic-damage constitutive model of concrete with features of the parameter certainty under axial compression. The finite element analysis results revealed that the increased ultimate bearing capacity of CFSSST stub columns compared with their carbon steel counterparts was mainly due to that the composite action of CFSSST stub columns is stronger than that of carbon steel counterparts. A further parametric study was carried out based on the verified model, and it was found that the stress contribution of the stainless steel tube is higher than the carbon steel tube. The stress nephogram was simplified reasonably in accordance with the limit state of core concrete and a theoretical formula was proposed to estimate the ultimate bearing capacity of square CFSSST stub columns using superposition method. The predicted results showed satisfactory agreement with both the experimental and FE results. Finally, the comparisons of the experimental and predicted results using the proposed formula and the existing codes were illustrated.

Further analysis on the flexural behavior of concrete-filled round-ended steel tubes

Fa-Xing Ding,Tao Zhang,Liping Wang,Lei Fu 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.30 No.2

A new form of composite column, concrete-filled round-ended steel tubes (CFRTs), has been proposed as piers or columns in bridges and high-rise building and has great potential to be used in civil engineering. Hence, the objective of this paper presents an experimental and numerical investigation on the flexural behavior of CFRTs through combined experimental results and ABAQUS standard solver. The failure mode was discussed in detail and the specimens all behaved in a very ductile manner. The effect of different parameters, including the steel ratio and aspect ratio, on the flexural behavior of CFRTs was further investigated. Furthermore, the feasibility and accuracy of the numerical method was verified by comparing the FE and experimental results. The moment vs. curvature curves of CFRTs during the loading process were analyzed in detail. The development of the stress and strain distributions in the core concrete and steel tube was investigated based on FE models. The composite action between the core concrete and steel tube was discussed and clarified. In addition, the load transfer mechanism of CFRT under bending was introduced comprehensively. Finally, the predicted ultimate moment according to corresponding designed formula is in good agreement with the experimental results.

Behavior of headed shear stud connectors subjected to cyclic loading

Fa-xing Ding,Guo-an Yin,Hai-bo Wang,Liping Wang,Qiang Guo 국제구조공학회 2017 Steel and Composite Structures, An International J Vol.25 No.6

The objective of this study is to investigate the actual behavior of studs in structures under earthquake load through laboratory tests and numerical simulation. A test program including eighteen specimens was devised with consideration of different concrete strengths and stud diameters. Six of specimens were subjected to monotonically increasing loading while the others were subjected to cyclic loading. Mechanical behavior including the failure mechanism, load-slip relationship, stiffness degradation, energy dissipation and the damage accumulation was obtained from the test results. An accurate numerical model based on the ABAQUS software was developed and validated against the test results. The results obtained from the finite element (FE) model matched well with the experimental results. Furthermore, based on the experimental and numerical data, the design formulas for expressing the skeleton curve were proposed and the simplified hysteretic model of load versus displacement was then established. It is demonstrated that the proposed formulas and simplified hysteretic model have a good match with the test results.