Extreme Electron-Phonon Coupling in Boron-based Layered Superconductors

The phonon-mode decomposition of the electron-phonon coupling in the MgB2-like system Li_{1-x}BC is explored using first principles calculations. It is found that the high temperature superconductivity of such systems results from extremely strong coupling to only ~2% of the phonon modes. Novel characteristics of E_2g branches include (1) ``mode lambda'' values of 25 and greater compared to a mean of $\sim 0.4$ for other modes, (2) a precipitous Kohn anomaly, and (3) E_2g phonon linewidths within a factor of ~2 of the frequency itself, indicating impending breakdown of linear electron-phonon theory. This behavior in borne out by recent inelastic x-ray scattering studies of MgB2 by Shukla et al.Comment: 4 two-column pages, 4 figures. Equations simplified. Figure 4 changed. Comparison with new data include

Choroid plexus papilloma in a Rottweiler: computed tomographic, gross morfological and histological features

Among the tumors affecting the choroid plexus in dogs, the papilloma ranks second place in incidence after cell carcinoma tumors. Presumptive diagnosis can be made through imaging methods, such as computed tomography and magnetic resonance images. Definitive diagnosis of plexus choroid tumor is based on histopathological findings. This report presented the tomographic features of the brain in a 6-year-old intact female Rottweiler with choroid plexus papilloma. The computed tomography showed right lateral ventricle enlargement, midline deviation and an enhanced mass into the postcontrast phase. At necropsy, a mass on the floor of the right lateral ventricle was observed, associated with important ventricle dilatation. The histopathological analysis demonstrated the presence of neoplastic cell forms with papillary projections. The computed tomography proved to be an effective tool in the presumptive diagnosis of this kind of cerebral disorder