Objective To evaluate the mechanism of apoptosis of gastric cancer cells(SGC-7901) induced by the combination of TSA and GX15-070.Methods SGC-7901 cells were treated with GX15-070,TSA and combination of GX15-070 and TSA.Cell viability and cleaved caspase-3,Bcl-2 protein expression were detected by MTT and Western blot.Results Within a certain range of concentration(2.5 ~ 10 μmol/L) and increasing treatment time,GX15-070 decreased the survival of SGC-7901 cells.The difference in cell survival among all groups was statistically significant(P0.01).The difference in cell survival among TSA group,GX15-070 group and the combination group was statistically significant(P0.01).Western blot analysis showed that Bcl-2 significantly reduced,but the levels of cleaved caspase-3 increased after the combination treatment.Conclusion TSA enhances the apoptotic effect of GX15-070 cells,its mechanisms may be involved in the up-regulation of cleaved caspase-3 and down-regulation of Bcl-2 expression in this process.
Abstract To ensure the safety of sliding base (SB) structures, the peak sliding displacement (PSD) should not exceed the predetermined sliding displacement threshold. Therefore, the PSD is an important response quantity that should be evaluated in design. In this chapter, the probability distribution of the PSD at a given level of ground motion intensity, and the influence of the vertical earthquake component and various structural and ground motion characteristics on the PSD are investigated. Simplified equations for estimating the PSD are also developed for design purposes.
The sliding base (SB) technique is an efficient and economical approach to mitigating seismic damage of low-rise buildings in rural areas. Based on the previous work on single-story SB structures, this study investigates the earthquake forces acting on multistory SB structures. Response history analyses of SB structures subjected to three-component earthquake excitations were performed. The computed results indicate that the increase in the number of stories tends to reduce the mean value of the peak base shear but has little influence on the coefficient of variation of the peak base shear. The peak story shears of a multistory SB structure subjected to an earthquake ground motion are reached at different time instants for different stories. The distributions of the equivalent lateral forces for SB structures with different story numbers follow the same trend, and the equivalent lateral forces tend to concentrate at the upper floors as the normalized peak ground acceleration and mass ratio increase. Simplified equations for computing the distribution of equivalent lateral forces were developed for design purposes.
Hybrid coupled wall (HCW) systems, especially with properly designed steel coupling beams, are efficient lateral load resisting systems. To further improve the seismic resiliency of HCW structures after major earthquakes, a new hybrid system consisting of steel plate composite structural wall piers and steel coupling beams with a replaceable fuse was developed. This paper presents an experimental program of three half-scaled subassemblies subjected to pseudo-static cyclic loading. Each test specimen consisted of two segments of composite wall piers and a steel coupling beam with and without a replaceable fuse. The details of the wall piers were identical for the three subassemblies, but three different coupling beams with the same span/depth ratio were used. One subassembly using a steel coupling beam without a replaceable fuse served as the control specimen, which was loaded up to 10% chord rotation following a preselected loading protocol. The other two specimens employed the new hybrid system. The fuse in these two subassemblies was replaced in situ after subjecting the coupling beam to 2% chord rotation, and the specimen was subsequently loaded up to 10% chord rotation. A detailed evaluation of the test results indicates that the new hybrid system can exhibit excellent performance and the replaceable fuse (and its connection details) proved to be a reliable technique to restore the performance after subjecting the coupling beam to chord rotations that are expected during design-level earthquakes. The load transfer mechanism and seismic performance varied depending on the details of the replaceable details of steel coupling beams.
A number of experimental and analytical studies have been conducted on the axial compressive behavior of square concrete-filled steel tubular (CFST) columns, but there still exist several controversies on this issue because the loads sustained by the concrete infill and the steel tube cannot be accurately measured in a conventional axial loading test. In this study, an innovative test method was devised to directly measure the load components of square CFST columns under axial compression. Five specimens with different width-to-thickness ratios were fabricated and tested. The factors that may affect the compressive strength of concrete in square CFST columns were investigated, and it was found that the difference between the compressive strength of concrete in CFST columns and the corresponding cylinder strength was small and within the commonly accepted ranges. The measured compressive strengths of the steel tubes were compared to the available empirical formulas. It was determined that the ultimate strength of the steel tube can be reasonably estimated, but more research is needed to fully understand the post-local-buckling behavior of the steel tube and the effects of various factors. Design recommendations were proposed for the axial load capacity of square CFST columns. The existing stress-strain models for the concrete infill and the steel tube were assessed using the measured stress-strain relationships, and more credible stress-strain models were developed.
Sliding base (SB) systems are attractive options for protecting low-rise buildings in high-seismicity undeveloped rural areas. This study focuses on the peak sliding displacements (PSDs) of SB structures subjected to three-component earthquake excitations. Both the PSDs in the two principal directions and that with respect to the origin were investigated. The peak ground velocity (PGV) was selected as the ground-motion intensity measure (IM) because of its high correlation with the PSD and simplicity of use in design. The effect of the vertical ground-motion component on the PSDs is negligible. At a given level of normalized PGV, the probability distribution of the normalized PSD approximately follows a lognormal distribution. The relationship between the median normalized PSD and normalized PGV in each principal direction is close to that with respect to the origin, and the influence of the superstructure natural period and mass ratio is insignificant. When the normalized PGV is small, the median normalized PSDs corresponding to the nonpulse-like and near-fault pulse-like records are close to each other; when the normalized PGV exceeds a certain value (approximately 6–8 m/s), the median normalized PSD for the pulse-like records begins to exceed that for the nonpulse-like records, with the difference increasing monotonically as the normalized PGV increases. The lognormal standard deviations of the normalized PSDs are generally between 0.4 and 0.6 except for some cases in which the normalized PGV is small. Based on the numerical results, simplified equations were developed for generating fragility curves.
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