Ehlers and Kundt have provided an approximate procedure to demonstrate that gravitational waves impart momentum to test particles. This was extended to cylindrical gravitational waves by Weber and Wheeler. Here a general, exact, formula for the momentum imparted to test particles in arbitrary spacetimes is presented.

© 2013 Kosho, licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Discovery and Delineation of Dermatan 4-O-Sulfotransferase-1 (D4ST1)-Deficient Ehlers-Danlos ...

Two cases of Ehlers-Danlos syndrome (EDS) diagnosed on the basis of their clinical presentation are presented. EDS is a rare genetic disorder involving connective tissue of skin and joints, having a variety of presenting signs and symptoms. There is no specific therapy for this disease but it is important to diagnose it as it may end up in fatal complications.

What happens to a single, presynaptically quiescent synapse among a population of active synapses? In this issue of Neuron, Ehlers and colleagues show that, far from being eliminated, these inactive synapses are primed for potentiation and incorporation into a new neural circuit through an upregulation of NR2B-containing NMDA receptors.

Death from arterial bleeding or gastrointestinal perforation has previously been reported in more than 15 patients with the Ehlers-Danlos syndrome. On a basis of 100 personally examined patients and a review of published accounts, these events seem particularly likely to occur in two distinct and recognizable forms (the gravis and the ecchymotic forms) of the syndrome.

Arterial dissection is uncommon in young adults and there are usually underlying causes. This report describes 2 young patients with vascular complications after trivial injury who were diagnosed to have Ehlers-Danlos syndrome. One patient died while the other remains in a stable condition. Early clinical recognition of this syndrome is necessary so as to prevent mortality and reduce morbidity.