Cost-reducing traits for agonistic head collisions: a case for neurophysiology

Many animal species have evolved extreme behaviors requiring them to engage in repeated high-impact collisions. These behaviors include mating displays like headbutting in sheep and drumming in woodpeckers. To our knowledge, these taxa do not experience any notable acute head trauma, even though the deceleration forces would cause traumatic brain injury in most animals. Previous research has focused on skeletomuscular morphology, biomechanics, and material properties in an attempt to explain how animals moderate these high-impact forces. However, many of these behaviors are understudied, and most morphological or computational studies make assumptions about the behavior without accounting for the physiology of an organism. Studying neurophysiological and immune adaptations that co-vary with these behaviors can highlight unique or synergistic solutions to seemingly deleterious behavioral displays. Here, we argue that selection for repeated, high-impact head collisions may rely on a suite of coadaptations in intracranial physiology as a cost-reducing mechanism. We propose that there are three physiological systems that could mitigate the effects of repeated head trauma: (i) the innate neuroimmune response, (ii) the glymphatic system, and (iii) the choroid plexus. These systems are interconnected yet can evolve in an independent manner. We then briefly describe the function of these systems, their role in head trauma, and research that has examined how these systems may evolve to help reduce the cost of repeated, forceful head impacts. Ultimately, we note that little is known about cost-reducing intracranial mechanisms making it a novel field of comparative study that is ripe for exploration.

A New High Strain-Rate Biaxial Experiment to Validate Constitutive Models for Polymers

We have developed a new high strain rate experiment in biaxial tension that allows for constitutive model validation at engineering strain rates from 50/s to over 1000/s. In the experiment, a flat disk of the material is clamped at a fixed radial distance. A rail-guided impact sled with a hemispherical impact head is released from the desired height and impacts the disk at the center, potentially deforming the sample to failure. Drop height and impact mass can be varied to modify peak strain rate and impact energy, and the wide range of test conditions allow for testing to be performed on many classes of materials, including thermoplastics and elastomers. The stress and strain fields are calculated using finite element simulations with the proposed constitutive model, and the constitutive model is validated by matching the force versus displacement data of the impact head recorded during experiment to the simulation. In this paper, we discuss results from the experiment and finite element simulations of the experiment on PA (polyamide, nylon) and PEEK (polyether ether ketone). The new experiment allows for validation and refinement of constitutive models, including failure, at high strain rates and in a multiaxial stress state.

Discrete Analysis of Maize Ear at Different Impact Head

In order to find the best impact head and threshing moisture content to damage the arrangement law of maize ear,the impact test with different varieties and different moisture of the maize ear is carried out in the drop impact test bench. The experimental result shows that the breakage rate of kernel is smaller and the discrete effect of kernel is better than others in the the action of impact head when moisture content of the maize ear belongs to 14%-20% or less than 12%. The wedge impact head is the most suitable for maize kernel threshing than other impact heads.The effect of maize varieties to the breakage rate is not obvious. The research results can provide a theoretical reference for the low damage threshing method of further research.

Efficacy of an Intense Rifle Fencing Training

The present study aimed to analyze the effectiveness of an intensive rifle fencing training based on a couple of the most effective fencing techniques compared to a traditional fencing training. 20 male professional soldiers of Spanish Army (28.6±2.4 years) were randomly divided in an experimental group (n: 10) and control group (n: 10). After 1 h rifle training sessions during 6 days, soldiers conducted simulated close quarter combats with rifles. Results showed that the experimental group obtained higher number of victories (17.0 vs. 7.0), number of techniques used (13.0 vs. 6.0), and had variations in body location of impact (head, trunk, legs and arms vs. head, trunk and arms) than control group. The experimental rifle fencing training focused on selected fencing techniques was more effective than the traditional rifle fencing training focused on a higher technical repertory.

A novel shock isolator for heavy structure installation

During the heavy structure installation process, any external disturbance may result in a huge impact on the substructure due to the extremely large mass involved, which may damage the whole structure permanently. Therefore, a reliable shock isolator for the installation interface is very important in such applications. In this study, a novel shock isolator based on a hydraulic damper is presented. It has been designed with an optimized throttling orifice to dissipate the energy efficiently and with air bags to store energy. Considering the maximal relative travel range of the isolator within a specified physical limit, the design is formulated as an optimization problem to minimize the peak acceleration during the impact and finalized as a constant force isolator. A mathematical model of the isolator is established and a prediction of its performance is obtained through some simulations. Experiments are performed to evaluate the theoretical model and it is found that the experimental data agree with the theoretical prediction very well, and thus validates the design. The influence of initial oil pressure and the material of elastic impact head are also investigated. The results show that higher initial oil pressure increases the peak acceleration, while the material of the elastic impact head has no significant effect on that.