In nature, several seabirds (e.g., gannets and boobies) dive into water at up to 24 m/s as a hunting mechanism; furthermore, gannets and boobies have a slender neck, which is potentially the weakest part of the body under compression during high-speed impact. In this work, we investigate the stability of the bird's neck during plunge-diving by understanding the interaction between the fluid forces acting on the head and the flexibility of the neck. First, we use a salvaged bird to identify plunge-diving phases. Anatomical features of the skull and neck were acquired to quantify the effect of beak geometry and neck musculature on the stability during a plunge-dive. Second, physical experiments using an elastic beam as a model for the neck attached to a skull-like cone revealed the limits for the stability of the neck during the bird's dive as a function of impact velocity and geometric factors. We find that the neck length, neck muscles, and diving speed of the bird predominantly reduce the likelihood of injury during the plunge-dive. Finally, we use our results to discuss maximum diving speeds for humans to avoid injury.diving | seabirds | buckling | injury | water entry N ature contains several species of creatures that interact with the air-water interface (1). A number of bird species are able to dive into water from the air as a hunting mechanism (e.g., kingfishers, terns, and gannets), a behavior known as plunge-diving (2, 3). Some seabirds, like the northern gannet, are highly specialized plunge-divers, making 20-100 dives per foraging trip, diving from heights of 5-45 m, and attaining speeds of more than 20 m/s (4-7). Thus, the bird's structure and behavior have presumably evolved to withstand a variety of high dynamic stresses, because no injuries have been reported in plunge-diving seabirds. Biologists have previously focused on the diving behavior in terms of ecological factors, such as diving depths, prey species, and hunting success rate (8-10), and physiological features, such as the role of vision while crossing the air-water interface (11,12). Unique kinematic and morphological features during the dive have also been observed, such as having a sharp, arrow-like body posture and a straight, long, and slender neck (13,14). However, a mechanical understanding of plunge-diving birds is not well-established.To study such a phenomenon, Morus bassanus (hereafter gannets) and Sula leucogaster (hereafter boobies), from the Sulidae family, are used as a model species due to their highly specialized diving characteristics (5, 13). First, they plunge-dive at very high speeds, using that momentum to carry them to some depth. Then, they use their webbed feet and/or wings to propel themselves further underwater, like penguins and cormorants (15, 16). Although plunge-diving at high speeds allows the bird to dive deeper, it induces much larger stresses on the seabird's body than pursuit diving alone (13). The two main forms of plunge-diving observed are known as the V-shaped dive and the U-shaped dive (5). During ...
Purpose: The number of global health opportunities offered to medical students has increased over the past 20 years. Recognizing the growing prevalence of these experiences, a number of studies have shown that these types of exposures have a significant impact on medical students’ education. However, there is a paucity of literature on the educational impacts of short-term domestic service-learning trips, which can be more accessible due to fewer logistical and financial barriers. This mixed-methods qualitative/quantitative study aims to understand the impact of a domestic one-week service learning program on medical students’ educational development and career choices. Methods: The authors conducted a qualitative analysis of journal entries written by a cohort of students during a domestic weeklong service trip. They also administered a survey to all students who had participated in the program between 2009–2016. Results: In 88.6% (n = 31) of the journal entries, students reported learning about border town life, Native American health, and rural medical practice. In 42.8% (n = 15) of entries, participants described experiences they felt would impact their future medical career decisions. The students’ reflections also revealed implicit benefits such as becoming aware of privilege within society (n = 14, 40.0%). The majority of survey respondents reported that the trip improved their medical education and influenced the field and location of their future/current practice. Conclusion: This study suggests that domestic short-term service-learning trips impact medical students’ immediate educational development and may influence their future career plans. Further investigation into the local community’s perceptions of this service-learning trip will provide greater understanding of the impact on all involved.
Jumping out of water is a phenomenon exhibited by a variety of aquatic and semi-aquatic animals. Yet, there is no common groundwork that clarifies the physical constraints required to jump out of water. In this study, we elucidate the physical conditions required for an animal to jump out of water. More than 100 jumps are analysed over five taxonomic groups. By balancing the power produced by animals with drag-induced dissipation, we expect that maximum jumping height, H , scales with body length, L , as H / L ∼ L −1/3 ∼ Fr 2 , where the Froude number, Fr, is a ratio of inertia to gravity. To identify jumping regimes, simplified experiments are conducted by shooting axisymmetric bodies through the water surface. Here, we see a transition in which partial exits scale as H / L ∼ Fr and complete exits scale as H / L ∼ Fr 2 . A bioinspired robotic flapping mechanism was designed to mimic the fast motion of impulsive jumping animals. When exiting water, the robot carries a large volume of fluid referred to as an entrained mass. A theoretical model is developed to predict the jumping height of various water-exiting bodies, which shows that the mass of the entrained fluid relative to the mass of the body limits the maximum jumping height. We conclude that the lack of entrained fluid allows animals to reach extraordinary heights compared to our water-exiting robots.
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