Study on mechanism of improving efficiency of permanent-magnet small ball-end magnetorheological polishing by increasing magnetorheological fluid temperature.

Permanent-magnet small ball-end magnetorheological polishing method can be used to polish the small part with complex structure. However, the material removal rate of this method is low, which is difficult to improve the output and reduce the cost. In this research, the effect of magnetorheological fluid temperature on the material removal rate is theoretically analyzed by measuring the effect of temperature on the flow properties of magnetorheological fluid, establishing the hydrodynamic model of polishing zone and solving the material removal parameters. It is found that with the increase of the magnetorheological fluid temperature, the polishing relative velocity increases accordingly, which can promote the improvement of material removal rate. But the shear stress decreases accordingly, which inhibits the improvement of material removal rate. The verification experiment results show that the promoting effect can exceeds the inhibitory effect, so that the material removal rate increases with the increase of magnetorheological fluid temperature. When the magnetorheological fluid temperature increases to 60 °C, the material removal rate is improved by 108.4% and the polished surface roughness Sa can reach 14.9 nm. Therefore, increasing the magnetorheological fluid temperature can significantly improve the efficiency of permanent-magnet small ball-end magnetorheological polishing and obtain high quality polished surface.

SUMOylation of HSP27 by small ubiquitin-like modifier 2/3 promotes proliferation and invasion of hepatocellular carcinoma cells.

Primary hepatocellular carcinoma (PHC) is a major health problem worldwide and is one of the 10 most commonly diagnosed cancers in China. Heat shock protein 27 (HSP27) were found to be overexpressed in a wide range of malignancies including PHC, however, post-translational modification of HSP27 still needs exploration in PHC. Recently, SUMOylation, an important post-translational modification associating with the development of many kinds of cancers has been intensively studied. In the current study, mRNA and protein level of HSP27 in archived tumor samples representing various pathological characteristics of PHC were examined, and modification of HSP27 by SUMO2/3 was investigated. HSP27 were expressed abundantly in patients' tumor tissues, and found to be associated with pathological progression. Besides, HSP27 was also elevated significantly in liver cancer cell lines Huh7 and HepG2 compared with human hepatocyte cells L02. Furthermore, knockdown of HSP27 was found to be associated with the decreased proliferation and invasion ability in Huh7 and HepG2 cells. Immunofluorescence assay showed that HSP27 and SUMO2/3 were co-localized in the subcellular, and co-immunoprecipitation verified the interaction between HSP27 and SUMO2/3. Overexpression of SUMO2/3 upregulated the HSP27 protein level and promotes Huh7 and HepG2 cell proliferation and invasion, and vice versa when the SUMO2/3 was knockdown. Taken together, increased protein level of HSP27 through SUMO2/3-mediated SUMOylation plays crucial roles in the progression of PHC, and this finding may shed light on developing potential therapeutic targets for PHC.