894 research outputs found
Impact behavior of honeycombs under combined shear-compression. Part II: Analysis
AbstractIn this paper, a numerical virtual model of honeycomb specimen as a small structure is used to simulate its combined shear-compression behavior under impact loading. With ABAQUS/Explicit code, the response of such a structure made of shell elements is calculated under prescribed velocities as those measured in the combined shear-compression tests presented in Part I of this study.The simulated results agree well with the experimental ones in terms of overall pressure/crush curves and deformation modes. It allows for the determination of the separated normal behavior and shear behavior of honeycomb specimen under dynamic combined shear-compression. It is found that the normal strength of honeycombs decreases with increasing shearing load. Quasi-static calculations were also performed and a significant dynamic strength enhancement found in experiments was validated again in the numerical work. A crushing envelope in normal strength vs. shear strength plane was obtained on the basis of these simulations
The Analysis of SKP1 Gene Expression in Physiological Male Sterility Induced by Chemical Hybridizing Agent SQ-1 in Wheat (Triticum aestivum L.)
Physiological male sterility induced by the chemical hybridizing agent (CHA) overcomes problems of maintenance of sterile lines and restorers. However, the mechanism of sterility is unclear. The process of tapetum of CHA-treated ‘Xi’nong 2611’ at uninucleate, binucleate and trinucleate were compared with control to determine if tapetum varying differently during developmental stages. Tapetal degradation in CHA-treated ‘Xi’nong 2611’ began at late uninucleate stage, somewhat earlier than control plants. Cytological observations indicated that the gradual degradation of the tapetum in CHA-treated ‘Xi’nong 2611’ was initiated and terminated earlier than in the control. These findings implied that CHA-induced male sterility was related to abnormally early tapetal degradation. In order to indicate the role of the SKP1 gene in fertility/sterility in wheat, its expression was assessed in anthers at uninucleate, binucleate and trinucleate stages. SKP1 expression was reduced in the later developmental stages, and there was an obvious decrease from the uninucleate to trinucleate stages. Higher expression of the SKP1 gene occurred in ‘Xi’nong 2611’ compared to CHA-treated ‘Xi’nong 2611’. This implied that SKP1 gene expression was inhibited during the fertility transformation process and was related to transformation from fertility to sterility. Moreover, the results from this study suggest that SKP1 plays an essential role of conducting fertility in physiological male sterility
Magnetic phase diagram in EuLaFeAs single crystals
We have systematically measured resistivity, susceptibility and specific heat
under different magnetic fields (H) in EuLaFeAs single
crystals. It is found that a metamagnetic transition from A-type
antiferromagnetism to ferromagnetism occurs at a critical field for magnetic
sublattice of . The jump of specific heat is suppressed and shifts to
low temperature with increasing H up to the critical value, then shifts to high
temperature with further increasing H. Such behavior supports the metamagnetic
transition. Detailed H-T phase diagrams for x=0 and 0.15 crystals are given,
and possible magnetic structure is proposed. Magnetoresistance measurements
indicate that there exists a strong coupling between local moment of
and charge in Fe-As layer. These results are very significant to understand the
underlying physics of FeAs superconductors.Comment: 5 pages, 4 figure
Characterization of starch synthetic genes and starch granule during seeds development between synthetic hexaploid wheat and its parents
To study the development of starch granules in polyploid wheats, we investigated the expression of starch synthetic genes between the synthetic hexaploid wheat SHW-L1, its parents T. turgidum AS2255 and diploid Ae. tauschii AS60. The synthetic hexaploid wheat SHW-L1 showed significantly higher starch content and grain weight than its parents. Scanning electron microscopy (SEM) showed that SHW-L1 rapidly developed starch granules than AS2255 and AS60. The amount of B-type granule in AS60 was less than that in SHW-L1 and AS2255. RT-qPCR result showed that the starch synthetic genes AGPLSU1, AGPLSU2, AGPSSU1, AGPSSU2, GBSSI, SSIII, PHO1 and PHO2 expressed at earlier stages with larger quantity in SHW-L1 than in its parents during wheat grain development. The expression of the above mentioned genes in AS60 was slower than in SHW-L1 and AS2255. The expression pattern of starch synthase genes was also associated with the grain weight and starch content in all three genotypes. The results suggested that the synthetic hexaploid wheat inherited the pattern of starch granule development and starch synthase gene expression from tetraploid parent. The results suggest that tetraploid wheat could plays more important role for starch quality improvement in hexaploid wheat
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