Dynamical Boson Stars

The idea of stable, localized bundles of energy has strong appeal as a model for particles. In the 1950s John Wheeler envisioned such bundles as smooth configurations of electromagnetic energy that he called {\em geons}, but none were found. Instead, particle-like solutions were found in the late 1960s with the addition of a scalar field, and these were given the name {\em boson stars}. Since then, boson stars find use in a wide variety of models as sources of dark matter, as black hole mimickers, in simple models of binary systems, and as a tool in finding black holes in higher dimensions with only a single killing vector. We discuss important varieties of boson stars, their dynamic properties, and some of their uses, concentrating on recent efforts.Comment: 79 pages, 25 figures, invited review for Living Reviews in Relativity; major revision in 201

A Rare Case of Idiopathic Failure of a Bioprosthetic Mitral Valve

A 65-year-old female with a significant history of two previous mitral valve replacement surgeries for mitral regurgitation was found to have severe mitral regurgitation again. She was determined to have a flail anterior mitral valve leaflet and underwent redo open sternotomy mitral valve replacement. This report serves to provide an example of an uncommon case of valve failure in an effort to alert clinicians to this potential complication

Atomic H diffusion and C etching in multilayer graphene monitored using a y based optical sensor

In this work, the authors expose transferred multilayer graphene on a yttrium based hydrogen sensor. Using spectroscopic ellipsometry, they show that graphene, as well as amorphous carbon reference films, reduce diffusion of hydrogen to the underlying Y layer. Graphene and C are both etched due to exposure to atomic H, eventually leading to hydrogenation of the Y to YH2 and YH3. Multilayer graphene, even with defects originating from manufacturing and transfer, showed a higher resistance against atomic H etching compared to amorphous carbon films of a similar thickness