ABSTRACT
Exercise can promote brain health in all the ages, directly or indirectly. In early childhood and adolescence, exercise can increase cardiorespiratory fitness to optimize the neuronal environment to benefit cerebral maturation and cognitive de-velopment. In mid-life, exercise may maintain cognitive function by increasing cerebral gray volume and cardiovascular fitness, and preventing a lot of neurobiological events which result in cognitive decline later in life. Finally, regular exer-cise in late life is very important for integrity of brain white matter, cardiorespiratory fitness, and prevention of future de-cline.
ABSTRACT
Objective To study the mechanical properties of PVP/PVA composite hydrogel and its interaction principle based on the molecular dynamics (MD) theory. Methods MD simulation was applied to investigate mechanical properties and radial distribution functions of PVP, PVA and their mixed system PVP/PVA. Results Compared with the pure PVP, mechanical properties of PVP/PVA were significantly improved, and not affected by temperature. The interaction between PVA and PVP was expected to occur through the interchain hydrogen bonding between the oxygen atom of PVP and the hydroxyl group of PVA. Conclusions MD method revealed the interaction mechanism of PVP/PVA hydrogel at molecular microscopic level and proved it better than pure PVP. Meanwhile, its mechanical properties were stable at different environment temperatures. These results provide a reliable theoretical research method for studying the fabrication process of hydrogel prosthesis in clinic and its mechanical properties.