It's in the loop: shared sub-surface foot kinematics in birds and other dinosaurs shed light on a new dimension of fossil track diversity

The feet of ground-dwelling birds retain many features of their dinosaurian ancestry. Experiments with living species offer insights into the complex interplay among anatomy, kinematics and substrate during the formation of Mesozoic footprints. However, a key aspect of the track-making process, sub-surface foot movement, is hindered by substrate opacity. Here, we use biplanar X-rays to image guineafowl walking through radiolucent substrates of different consistency (solid, dry granular, firm to semi-liquid muds). Despite substantial kinematic variation, the foot consistently moves in a looping pattern below ground. As the foot sinks and then withdraws, the claws of the three main toes create entry and exit paths in different locations. Sampling these paths at incremental horizons captures two-dimensional features just as fossil tracks do, allowing depth-based zones to be characterized by the presence and relative position of digit impressions. Examination of deep, penetrative tracks from the Early Jurassic confirms that bipeds had an equivalent looping response to soft substrates approximately 200 Ma. Our integration of extant and extinct evidence demonstrates the influence of substrate properties on sinking depth and sub-surface foot motion, both of which are significant sources of track variation in the fossil record of dinosaurs

Surgical management of children and young adults with the Wolff-Parkinson-White syndrome

The Wolff-Parkinson-White syndrome, as originally described, includes palpitations, tachycardia, and an abnormal electrocardiogram (short PR interval and wide QRS complex). The clinical manifestations are dependent upon a reentrant tachycardia supported by an accessory connection bridging the atrioventricular junction and frequently appear during the first two decades of life. Palpitations are the usual symptoms; less frequently, severe symptoms, such as syncope and sudden death, may result from very rapid atrioventricular conduction across the accessory connection during atrial fibrillation. We report the surgical management of 30 young patients with this syndrome, including 6 with life-threatening tachycardia. Surgical interruption of the accessory connection(s) was curative in 90% (27/30) of the patients; life-threatening symptoms were eliminated in the other three. Based on the limited knowledge of the natural history of the Wolff-Parkinson-White syndrome, the individual patient symptoms, and the electrophysiologic properties of each patient's accessory pathway(s), an algorithm is presented outlining the treatment options. This experience strongly suggests that surgical treatment of the Wolff-Parkinson-White syndrome is safe, effective, and possibly the preferred treatment for this disorder in selected young symptomatic patients.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/41585/1/380_2005_Article_BF02058591.pd