Effect of Microstructure on High-Speed Tensile Mechanical Properties of Ti-1300 Alloy.

It is usually required that Ti-1300 alloys be able to withstand a greater load under special conditions, such as the controllable collision of a space shuttle and rapid collision of an automobile. Because of a good combination of strength and toughness, Ti-1300 alloys are widely applied in the aerospace industry. However, during the service process, the alloy components inevitably bear extreme loads. This paper uses high-speed tensile technology to systematically study the effects of different strain rates on the deformation of the microstructure and deformation mechanism of Ti-1300 alloys and to clarify a relation between the microstructure and mechanical properties. The results show that no phase transformation occurs during the high-speed tensile process at strain rates of 200 s-1 and 500 s-1. The deformation mechanism is mainly due to dislocation slip. The fracture mode is ductile fracture at the two strain rates, due to the connection between micro-voids promoted by dislocation slip. The ultimate tensile strengths are 1227 MPa and 1368 MPa, the yield strengths are 1050 MPa and 1220 MPa, and the elongations are 11.3% and 10.4%, respectively. The present results provide theoretical guidance for the further application of metastable ß titanium alloys in working environments with high strain rates.

Three-Dimensional Modeling of Segregation Behavior during Solidification of a Sn-6 wt.% Pb Alloy.

In this study, a three-dimensional (3D) solidification model was developed that uses a SOLA algorithm to solve momentum equations and accelerate iterative convergence. The macrosegregation behavior of a sand-cast Sn-6 wt.% Pb alloy was numerically investigated by the developed 3D model. The experiment was carried out for a casting with one side in contact with a graphite chill and the other sides in contact with resin sand. The necessary precision of in-house-developed codes was validated by comparisons with experimentally measured cooling curves and lead concentration distribution. The limitations of the model in fitting experimental results well were discussed. A comparative study between simulations in two-dimensional (2D) and 3D cavities showed that although the general distribution pattern of macrosegregation was slightly affected, the details regarding segregation degree, solute composition distribution over the solidifying domain, solidification time and fluid flow pattern were different. For 2D simulations without boundary walls, the convection behavior was less complicated, and the cooling process was slowed down both in the casting and in the mold.

[PVT1 Promoted the Proliferation and Migration Ability of BMSCs in Glioma C6 Microenvironment].

OBJECTIVE: To investigate the changes in the proliferation and migration ability of bone marrow mesenchymal stem cells (BMSCs) after indirect co-culturing with glioma C6 cells, and to examine the role of plasmacytoma variant translocation 1 gene ( PVT1), a long non-coding RNA (lncRNA), in these changes. METHODS: After separation, cultivation and identification of BMSCs, BMSCs of good growth condition were picked out and indirectly co-cultured with glioma C6 cells in Transwell chambers. These cells are henceforth referred to as the co-culture group. Normal BMSCs cultured separately were the control group. CCK-8 and soft agar colony formation assay were used to examine the proliferation ability of the two groups of cells. Flow cytometry was used to examine the cell cycle. Wound healing assay and Transwell assay were used to explore the migration ability of the cells. Quantitative real-time PCR (qRT-PCR) was used to examine the genetic expression level of PVT1 in the two groups. The above-mentioned tests were repeated after the co-cultured BMSCs were transfected with si- PVT1 (si- PVT1 group) and si-NC (si-NC group). In addition, qRT-PCR was done to evaluate the expression of CyclinD1, a cell cycle protein gene, and matrix metalloproteinases 2 and 9 ( MMP2 and MMP9), the migration-related genes in the si- PVT1 and si-NC transfected co-cultured BMSCs. RESULTS: The BMSCs used in the present study possess the capability of osteogeneic and adipogenic differentiation. Compared with the control group, the co-cultured BMSCs had smaller size, disorderly arrangement and the lack of intercellular contact inhibition. The proliferation and migration ability was significantly enhanced, the proportions of S and G 2 phase cells greatly increased and the expression level of PVT1 was significantly up-regulated ( P<0.05) in the co-cultured group in comparison with those of the control group. When compared with the si-NC group, the si- PVT1 group showed inhibited proliferation and migration ability of the co-cultured BMSCs; the percentage of G 1 phase cells increased, while that of S phase decreased; the expression of PVT1, CyclinD1, MMP2 and MMP9 mRNA also decreased ( P<0.05) in the si- PVT1 group. CONCLUSION: The enhanced proliferation and migration ability of BMSCs in the glioma C6 microenvironment may be associated with the up-regulated expression of PVT1 .

[Indwelling the anterior urethral stent: a good treatment option for anterior urethral stricture].

OBJECTIVE: To observe the clinical effect of indwelling the anterior urethral stent in the treatment of anterior urethral stricture. METHODS: We included 38 patients with anterior urethral stricture in the treatment group, and another 38 in the control, the former treated by indwelling the anterior urethral stent, and the latter by urethral dilatation. Then we analyzed the clinical results by comparing the Qmax, urinary hesitancy and numbers of urethral dilations between the two groups. RESULTS: Compared with the controls, the patients of the treatment group showed an obvious increase in Qmax, a significant decrease in the number of urethral dilatations, and a marked improvement of the quality of life. Six months after the stent removal, there were significantly more patients with Qmax > 15 ml/s in the treatment group than in the control (P < 0.05). CONCLUSION: Indwelling the anterior urethral stent is a desirable option for the treatment of anterior urethral stricture, which is simple, safe, effective and reliable, and can be applied to general clinical practice.