Background: Graphitization behavior of diamond has received an increasing interest in nanoscale machining of some hard and brittle materials. Diamond has always been an important and excellent tool material in cutting area. However, the graphitization of the diamond tool is inevitable when it was used in special conditions. It is indicated that the graphitization of diamond crystal has great influence on the wear resistance of diamond cutting tool. The graphitization behavior needs to be investigated extensively in nanoscale with an atomic view. Molecular dynamics simulation provides a useful tool for understanding of the graphitization mechanism of diamond. The investigation on graphi-tization behavior of single crystal diamond can also provide a useful reference for the application of diamond cutting tool.Materials and Methods: In this paper, a molecular dynamics (MD) diamond crystal model is built to examine the graphitization behavior of diamond under various conditions. The sixfold ring method was employed to identify the structural characteristics of graphite and diamond. The effects of temperature and crystal orientation on the graphitization of diamond have been revealed. Considering the effect of temperature, the anisotropy of diamond graphitization against various crystal planes is presented and discussed carefully. The nano-metric cutting model of diamond tool evaluated by the sixfold ring meth-od also proves the graphitization mechanisms in atomic view.Results: Results indicate that the sixfold ring method is a reliable method to evaluate the graphitization behavior of diamond crystal. There exists a critical temperature of the graphitization of diamond. The results also show that {111} plane is more easy to get graphitization as compared with other crystal planes. However, {100} plane of diamond model presents the highest anti-graphitization property.Conclusion: The obtained results have provided the in-depth understanding on the wear of diamond tool in nano-metric machining and underpin the development of diamond cutting tool
Background: MicroRNAs (miRNAs) play important roles in the carcinogenesis and progression of hepatocellular carcinoma (HCC). Previous studies have shown that miR-3144 is down-regulated in HCC tissues. The present study investigated the expression and biological roles, underlying
mechanisms of miR-3144 in HCC cell lines. Methods and material: RT-qPCR analysis was performed to detect miR-3144 expression in the HCC cell lines and normal hepatic cell line. CCK-8 assay showed that the effect of miR-3144 expression on cell proliferation. Using wound healing assay
and Transwell assay to detect the effect of miR-3144 on cell invasion and migration of HCC. Flow cytometry assay showed that miR-3144 induced apoptotic cell death in the SK-HEP-1 cells. Luciferase reporter assay was performed to evaluate the interaction between miR-3144 and the Steap4 3′-UTR.
Western blotting assay were performed to investigate the effect of miR-3144 expression on the expression of CDK2, cyclinE1, p21, MMP2, MMP9 and Steap4. Results: MiR-3144 expression was downregulated in HCC cell lines. MiR-3144 overexpression inhibited the proliferation of HCC cells
via regulating CDK2, cyclinE1 and p21 in SK-HEP-1 cells. MiR-3144 suppressed the migration and invasion of HCC cells via decreasing the MMP2 and MMP9. Further, miR-3144 promotes cell apoptosis of HCC. Moreover, miR-3144 negatively regulated Steap4 expression by directly binding to the 3′-UTR
of Steap4 mRNA. Conclusion: Our results suggested that miR-3144 may be a novel target for future HCC therapy.
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