The aims of this study are to clarify the role of mTOR in mediating cerebral ischemic brain damage and the effects of rapamycin on ischemic outcomes. Ten minutes of forebrain ischemia was induced in rats, and their brains were sampled after 3 h, 16 h, and 7 days reperfusion for histology, immunohistochemistry and biochemical analysis. Our data demonstrated that cerebral ischemia resulted in both apoptotic and necrotic neuronal death; cerebral ischemia and reperfusion led to significant increases of mRNA and protein levels of p-mTOR and its downstream p-P70S6K and p-S6; elevation of LC3-II, and release of cytochrome c into the cytoplasm in both the cortex and hippocampus. Inhibition of mTOR by rapamycin markedly reduced ischemia-induced damage; suppressed p-Akt, p-mTOR, p-P70S6K and p-S6 protein levels; decreased LC3-II and Beclin-1; and prevented cytochrome c release in the two structures. All together, these data provide evidence that cerebral ischemia activates mTOR and autophagy pathways. Inhibition of mTOR deactivates the mTOR pathway, suppresses autophagy, prevents cytochrome c release and reduces ischemic brain damage.

Oblique shock waves are unavoidable in a rectangular hypersonic inlet, leading to a non-uniform flow field. While a significant body of the literature exists regarding the shock train modeling in a uniform incoming flow condition, few efforts have focused on the shock train behavior considering the influence of the shock wave boundary layer interactions. A low-order dynamic model of the shock train has been constructed with the help of the free interaction theory and a 1-D analysis approach. Experimental and numerical investigations have been carried out to evaluate the low-order model. The results show that the model has the capability of qualitatively analyzing the shock train behavior. In the cases with incident shocks, the rapid forward movement of the shock train has been observed by experiment. Besides this phenomenon was also modeled using the low-order model. Schlieren images show that when the shock train approaches the interaction zone, its behavior is characterized by oscillation and then follows a rapid forward movement with a linear increasing backpressure at 2.7 Ma. This phenomenon is analyzed theoretically based on the free interaction theory. Meanwhile with the help of the direct numerical simulation results from some existing studies, the flow structures in the interaction region and the following boundary layer also provide the evidence.

No abstract

The finite-element approach of absolute nodal coordinate formulation (ANCF) is a possible way to simulate the deployment dynamics of a large-scale mesh reflector of satellite antenna. However, the large number of finite elements of ANCF significantly increases the dimension of the dynamic equations for the deployable mesh reflector and leads to a great challenge for the efficient dynamic simulation. A new parallel computation methodology is proposed to solve the differential algebraic equations for the mesh reflector multibody system. The mesh reflector system is first decomposed into several independent subsystems by cutting its joints or finite-element grids. Then, the Schur complement method is used to eliminate the internal generalized coordinates of each subsystem and the Lagrange multipliers for joint constraint equations associated with the internal variables. With an increase of the number of subsystems, the dimension of simultaneous linear equations generated in the numerical solution process will inevitably increase. By using the multilevel decomposition approach, the dimension of the simultaneous linear equations is further reduced. Two numerical examples are used to validate the efficiency and accuracy of the proposed parallel computation methodology. Finally, the dynamic simulation for a 500 s deployment process of a complex AstroMesh reflector with over 190,000 generalized coordinates is efficiently completed within 78 hrs.