Experimental investigation of brain contusion characteristics and dynamic response in low-age children using an animal model.

INTRODUCTION: Brain contusion is a prevalent traumatic brain injury (TBI) in low-age children, bearing the potential for coma and fatality. Hence, it is imperative to undertake comprehensive research in this field. METHODS: This study employed 4-week-old piglets as surrogates for children and introduced self-designed devices for both free-fall drop impact tests and drop-hammer impact tests. The study explored the characteristics of brain contusion and dynamic responses of brain under these distinct testing conditions. RESULTS: Brain contusions induced by free-fall and drop-hammer conditions both were categorized as the coup injury, except that slight difference in the contusion location was observed, with contusion occurring mainly in the surrounding regions beneath the impact location under free-fall condition and the region just right beneath the impact location under drop-hammer condition. Analysis of impact force and intracranial pressure (ICP) curves indicated similar trends in impact forces under both conditions, yet different trends in ICPs. Further examination of the peak impact forces and ICPs elucidated that, with increasing impact energy, the former followed a combined power and first-order polynomial function, while the latter adhered to a power function. The brain contusion was induced at the height (energy) of 2 m (17.2 J), but not at the heights of 0.4, 0.7, 1, 1.35 and 1.7 m, when the vertex of the piglet head collided with a rigid plate. In the case of a cylindrical rigid hammer (cross-sectional area constituting 40 % of the parietal bone) striking the head, the brain contusion was observed under the energy of 21.9 J, but not under energies of 8.1 J, 12.7 J and 20.3 J. Notably, the incidence of brain contusion was more pronounced under the free-fall condition. CONCLUSIONS: These findings not only facilitate a comprehensive understanding of brain contusion dynamics in pediatric TBIs, but also contribute to the validation of theories and finite element models for piglet heads, which are commonly employed as surrogates for children.

Molecular dynamics simulations of friction process between diamond-like carbon and Si-DLC films.

Diamond-like carbon (DLC) films have been extensively studied over the past decades due to their unique combination of properties; in particular, silicon-doped DLC (Si-DLC) films are of significant interest for tribological effects, they had a very low friction coefficient and possessed the potential to improve wear performance in humid atmospheres and at higher temperatures. But many experimental results of the Si-DLC films showed that their tribological properties changed greatly on different silicon content. In the paper, molecular dynamics (MD) simulations were used to study microstructure of amorphous Si-DLC films and a sliding friction process between DLC and Si-DLC films on un-lubricated and oil-lubricated conditions respectively. The results show that silicon atoms are almost surrounded by carbon atoms in all Si-DLC films. The sp3/sp2 ratio in Si-DLC films increases with the increasing silicon content. After sliding, a transfer film between the DLC and Si-DLC films is formed on the un-lubricated condition. In contrast, a boundary lubrication layer is found on the oil-lubricated condition. Moreover, the friction forces on the un-lubricated condition are larger than those on the oil-lubricated condition.