ABSTRACT
The use of high-speed puncture mechanics for prey capture has been documented across a wide range of organisms, including vertebrates, arthropods, molluscs and cnidarians. These examples span four phyla and seven orders of magnitude difference in size. The commonality of these puncture systems offers an opportunity to explore how organisms at different scales and with different materials, morphologies and kinematics perform the same basic function. However, there is currently no framework for combining kinematic performance with cutting mechanics in biological puncture systems. Our aim here is to establish this framework by examining the effects of size and velocity in a series of controlled ballistic puncture experiments. Arrows of identical shape but varying in mass and speed were shot into cubes of ballistic gelatine. Results from high-speed videography show that projectile velocity can alter how the target gel responds to cutting. Mixed models comparing kinematic variables and puncture patterns indicate that the kinetic energy of a projectile is a better predictor of penetration than either momentum or velocity. These results form a foundation for studying the effects of impact on biological puncture, opening the door for future work to explore the influence of morphology and material organization on high-speed cutting dynamics.
ABSTRACT
BACKGROUND: Though several published reports have demonstrated the feasibility of conducting school-site cardiovascular risk factor screening programs as well as the ability of such programs to detect high-risk children and parents, less is known about their cognitive and behavioral impact. METHODS: Four Michigan elementary schools received a cardiovascular risk factor screening intervention twice between spring 1989 and spring 1990 and four other area schools served as comparison sites. All eight schools received the Michigan Model Comprehensive School Health Education Program. RESULTS: Among participating students (n = 1,166) and their parents (n = 514), significant favorable changes in relevant health knowledge as well as attitudes regarding nutrition and early detection of disease relative to comparison student (n = 480) and parents (n = 158), were observed. There was also a significant decrease in students' self-reported intake of high-fat foods and parents of children who participated were themselves significantly more likely to report having had their cholesterol and blood pressure tested. CONCLUSIONS: This quasi-experimental study suggests that school-based risk factor screening programs can positively influence the knowledge, attitude, and behavior of schoolchildren and their parents and may, therefore, represent a potentially effective adjunct to traditional curricular approaches to disease prevention and health education as well as an alternative means of early detection.
