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This paper studies the global bifurcations and multipulse chaotic dynamics of a four-edge simply supported honeycomb sandwich rectangular plate under combined in-plane and transverse excitations. Based on the von Karman type equation for the geometric nonlinearity and Reddy's third-order shear deformation theory, the governing equations of motion are derived for the four-edge simply supported honeycomb sandwich rectangular plate. The Galerkin method is employed to discretize the partial differential equations of motion to a three-degree-of-freedom nonlinear system. The six-dimensional nonautonomous nonlinear system is simplified to a three-order standard form by using the normal form method. The extended Melnikov method is improved to investigate the six-dimensional nonautonomous nonlinear dynamical system in a mixed coordinate. The global bifurcations and multipulse chaotic dynamics of the four-edge simply supported honeycomb sandwich rectangular plate are studied by using the improved extended Melnikov method. The multipulse chaotic motions of the system are found by using numerical simulation, which further verifies the result of theoretical analysis.

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The prenatal-to-postnatal transition is a pivotal process in the life cycle whereby an organism shifts from responding to intrauterine cues to undergoing extrauterine stresses with many physiological adaptations. However, the molecular basis underlying the evolutionarily conserved physiological adaptations remains elusive. Here, we analyze the transcriptomes of seven organs across developmental time points from five mammalian species by constructing computational co-expression networks and report a developmental shift of gene expression at the perinatal stage. The low-to-high and high-to-low expressed genes tightly coalesce in the functional categories and gene regulatory pathways that implicate the physiological adaptions during the prenatal-to-postnatal transition, including lipid metabolism, circadian rhythm, immune response, cell cycle, and cell division. The low-to-high and high-to-low expressed genes around the perinatal stage tend to form the mutually inhibitory toggle switch gene pairs linking the gene regulatory networks in response to the environmental changes. We thus propose the toggle switch model for the developmental shift of gene expression as a mechanic framework to investigate how the physiological adaptations occur during the prenatal-to-postnatal transition.