Obstacle avoidance in aerial pursuit.

Pursuing prey through clutter is a complex and risky activity requiring integration of guidance subsystems for obstacle avoidance and target pursuit. The unobstructed pursuit trajectories of Harris' hawks Parabuteo unicinctus are well modeled by a mixed guidance law feeding back target deviation angle and line-of-sight rate. Here we ask how their pursuit behavior is modified in response to obstacles, using high-speed motion capture to reconstruct flight trajectories recorded during obstructed pursuit of maneuvering targets.

Visual versus visual-inertial guidance in hawks pursuing terrestrial targets.

The aerial interception behaviour of falcons is well modelled by a guidance law called proportional navigation, which commands steering at a rate proportional to the angular rate of the line-of-sight from predator to prey. Because the line-of-sight rate is defined in an inertial frame of reference, proportional navigation must be implemented using visual-inertial sensor fusion. By contrast, the aerial pursuit behaviour of hawks chasing terrestrial targets is better modelled by a mixed guidance law combining information on the line-of-sight rate with information on the deviation angle between the attacker's velocity and the line-of-sight.

Perceptions of Veterinary Students at North Carolina State University about the Use of Animals in Teaching and Research.

Teaching through the use of animals is an integral part of veterinary education. In addition to interactions with privately owned animals, veterinary students often learn using cadavers and institutionally owned animals. Veterinary students also frequently participate in research involving animals.

Optimization of avian perching manoeuvres.

Perching at speed is among the most demanding flight behaviours that birds perform and is beyond the capability of most autonomous vehicles. Smaller birds may touch down by hovering, but larger birds typically swoop up to perch-presumably because the adverse scaling of their power margin prohibits hovering and because swooping upwards transfers kinetic to potential energy before collision. Perching demands precise control of velocity and pose, particularly in larger birds for which scale effects make collisions especially hazardous.

Viscoelastically active sutures - A stitch in time?

We present results to show that a commercially available polypropylene suture filament (Ethicon Prolene), following annealing and tensile creep can, after creep load removal, release viscoelastically stored energy over a period of several weeks. Specifically, over 0.1-1000 h, the suture undergoes a time-dependent contraction of ~4% and, following a short recovery time (~3 min) to a fixed strain, produces a progressively increasing recovery force of ~0.