Introduction: One of the hallmark symptoms of posttraumatic stress disorder (PTSD) is the impaired extinction of traumatic memory. Single prolonged stress (SPS) has been suggested as an animal model of PTSD, since SPS rats exhibited the impaired fear extinction. Oxytocin (OXT) has been recently suggested as a potential pharmacotherapy for treatment of PTSD. In this study, using SPS rats we inve...

The development of a wireless undulatory tadpole robot using ionic polymer–metal composite (IPMC) actuators is presented. In order to improve the thrust of the tadpole robot, a biomimetic undulatory motion of the fin tail is implemented. The overall size of the underwater microrobot prototype, shaped as a tadpole, is 96 mm in length, 24 mm in width, and 25 mm in thickness. It has one polymer fi...

The submerged swimming of the Florida manatee (Trichechus manatus latirostris), a subspecies of the West Indian manatee, was studied by filming individuals as they swam rectilinearly in a large pool at several rehabilitation centers. The swimming was analyzed using videography to detail the kinematics in conjunction with a hydromechanical model to determine the power output (P(t)) and propulsiv...

The effects of fluid elasticity on the swimming behavior of the nematode Caenorhabditis elegans are experimentally investigated by tracking the nematode's motion and measuring the corresponding velocity fields. We find that fluid elasticity hinders self-propulsion. Compared to Newtonian solutions, fluid elasticity leads to up to 35% slower propulsion. Furthermore, self-propulsion decreases as e...

We analyze the lateral undulatory motion of a natural or artificial snake or other slender organism that "swims" on land by propagating retrograde flexural waves. The governing equations for the planar lateral undulation of a thin filament that interacts frictionally with its environment lead to an incomplete system. Closures accounting for the forces generated by the internal muscles and the i...

What wavelengths do undulatory swimmers use during propulsion? In this work we find that a wide range of body/caudal fin (BCF) swimmers, from larval zebrafish and herring to fully-grown eels, use specific wavelength (ratio of wavelength to tail amplitude of undulation) values that fall within a relatively narrow range. The possible emergence of this constraint is interrogated using numerical si...

Echocardiographic studies were performed in 22 patients with atrial fibrillation and atrial flutter. In atrial flutter, the echocardiograms consistently demonstrated regular undulatory waves of the posterior left atrial wall and upper left interventricular septum coinciding with each flutter wave of the electrocardiogram. The mitral valve was slightly reopened by each flutter wave occurring aft...