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A walking robot consisting of double Stewarts parallel legs was designed by our research team in the past time, which was mainly used for the transportation of the wounded after the disaster. In order to promote stability of control locomotion and ensure invariably horizontal state of the robot platform in the process of motion, the central pattern generator (CPG) based on particle swarm optimization (PSO) is presented to optimize the kinematic model. The purpose of optimization is to solve the hysteresis problem of displacement variation among the electric cylinders. Moreover, the dynamic model of the robot is established, which can provide mechanical basis for the feedback of control signal and make the robot move stably. The simulation results show that the displacement hysteresis problem of the electric cylinders is solved well. Meanwhile, compared with simulation results based on GA-CPG method, it is demonstrated that the robot motion planned using PSO-CPG method has better motion stability and can avoid the impact of legs landing during the transition phase of the motion cycle. The experimental results show that the platform on the robot can maintain an invariably horizontal state, and the locomotion is more stable. It verifies the feasibility of PSO-CPG model and the correctness of the dynamic model of the parallel mobile rescue robot.
The Nlrp gene family contains 20 members and plays a pivotal role in the innate immune and reproductive systems in the mouse. During evolution, seven Nlrp4 gene copies (named from Nlrp4a to Nlrp4g). Nlrp4a–Nlrp4g have arisen that display specific or preferential ovarian expression patterns. However, the expression pattern and localization of Nlrp4g in mouse preimplantation embryo development are unknown. Here we report that Nlrp4g was highly expressed in mature oocytes and zygotes, then downregulated and not detected after the 2-cell embryo stage. NLRP4G protein remained present through the blastocyst stage and was mainly localized in the cytoplasm. Furthermore, overexpression of Nlrp4g in zygotes did not affect normal development in terms of the rate of blastocyst formation. These results provide the first evidence that NLRP4G is a maternal factor that may play essential role during zygotic genome activation in the mouse.
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