A stick-slip piezo-driven linear actuator to output bidirectional motion is proposed. The actuator has a compact structure, with a length, width, and height of approximately 80, 80, and 20 mm in the X, Y, and Z directions, respectively. A prototype of the actuator was designed, fabricated, and analysed. An experimental system was established to evaluate the output performances of the actuator, including the stepping displacement and the ratio of backward motion. The experimental results indicated that the maximum speeds of the forward and reverse motions were 2.01 and 2.34 mm s −1 , respectively. The maximum vertical load was 380 g. The stepping displacement was 0.89 μm, with a control voltage of 20 V and a control-signal frequency of 220 Hz. When the driving frequency was >220 Hz, the actuator eliminated the backward motion under no load, and the step efficiency of the actuator reached 100%. The optimal working conditions of the actuator were a driving frequency of 220-300 Hz and a constant driving voltage of 100 V.

Pancreatic cancer is a fatal disease with a high mortality rate and poor prognosis worldwide. The aberrant expression of micrornas (mirs) is associated with cancer development and progression. The present study aimed to evaluate the functional role of mir-142-5p in migration and invasion, and investigated its underlying molecular mechanism in pancreatic cancer cells. First, it was identified that miR-142-5p expression was downregulated in pancreatic cancer tissues and cell lines by reverse transcription-quantitative polymerase chain reaction. Furthermore, phosphoinositide-3-kinase catalytic subunit α (PIK3CA) was identified as a target of miR-142-5p. The expression of PiK3ca was upregulated in tumor tissues and its expression was negatively regulated by mir-142-5p expression. notably, overexpression of mir-142-5p inhibited the proliferation, migration and invasion of Panc1 cells, while PiK3ca reversed this inhibition. in addition, mir-142-5p suppressed the expression of focal adhesion kinase (FaK) and matrix metalloproteinase (MMP)9, as well as phosphorylated protein kinase B (aKT) protein level, while PiK3ca reversed the suppression induced by mir-142-5p. in conclusion, mir-142-5p functions as a tumor suppressor, which inhibits the migration and invasion of pancreatic cancer by suppressing the expression of FaK and MMP9, as well as the phosphatidylinositol 3-kinase/aKT signaling pathway by targeting PIK3CA. These findings suggest that mir-142-5p may be a novel therapeutic target for the treatment of pancreatic cancer.

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Motion speed is an important parameter of stick-slip piezoelectric actuators. However, most of the existing stick-slip piezoelectric actuators achieve a high motion speed by operating under a quite high driving frequency. Operation under high frequency will affect the motion stability and as well accelerate the wear of the contact surfaces. To realize relatively high speed under a relatively low operation frequency, here a specific L-shape flexure hinge was employed to design the stick-slip piezoelectric actuator. Its structure design, working principle and processes, structure parameter selection, and output performances were studied in detail. The experimental results indicated that the designed actuator could achieve a maximum motion speed of 16.67 mm s −1 under the driving frequency of 800 Hz. This operation frequency was much lower than those employed in previous actuators for achieving a similar motion speed. By comparative analysis, it was shown that the designed actuator also maintained good minimum stepping displacement and loading capacity. These features would be useful for the practical applications of stick-slip piezoelectric actuators.

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