Electromagnetic effects of neutrinos in an electron gas

We study the electromagnetic properties of a system that consists of an electron background and a neutrino gas that may be moving or at rest, as a whole, relative to the background. The photon self-energy for this system is characterized by the usual transverse and longitudinal polarization functions, and two additional ones which are the focus of our calculations, that give rise to birefringence and anisotropic effects in the photon dispersion relations. Expressions for them are obtained, which depend on the neutrino number densities and involve momentum integrals over the electron distribution functions, and are valid for any value of the photon momentum and general conditions of the electron gas. Those expressions are evaluated explicitly for several special cases and approximations which are generally useful in astrophysical and cosmological settings. Besides studying the photon dispersion relations, we consider the macroscopic electrodynamic equations for this system, which involve the standard dielectric and permeability constants plus two additional ones related to the photon self-energy functions. As an illustration, the equations are used to discuss the evolution of a magnetic field perturbation in such a medium. This particular phenomena has also been considered in a recent work by Semikoz and Sokoloff as a mechanism for the generation of large-scale magnetic fields in the Early Universe as a consequence of the neutrino-plasma interactions, and allows us to establish contact with a specific application in a well defined context, with a broader scope and from a very different point of view.Comment: Revtex 20 page

Cooperative resonance linewidth narrowing in a planar metamaterial

We theoretically analyze the experimental observations of a spectral line collapse in a metamaterial array of asymmetric split ring resonators [Fedotov et al., Phys. Rev. Lett. 104, 223901 (2010)]. We show that the ensemble of closely-spaced resonators exhibits cooperative response, explaining the observed system-size dependent narrowing of the transmission resonance linewidth. We further show that this cooperative narrowing depends sensitively on the lattice spacing and that significantly stronger narrowing could be achieved in media with suppressed ohmic losses.Comment: 19 pages, 6 figures, to appear in New Journal of Physic

Negative effective permeability and left-handed materials at optical frequencies

We present here the design of nano-inclusions made of properly arranged collections of plasmonic metallic nano-particles that may exhibit a resonant magnetic dipole collective response in the visible domain. When such inclusions are embedded in a host medium, they may provide metamaterials with negative effective permeability at optical frequencies. We also show how the same inclusions may provide resonant electric dipole response and, when combining the two effects at the same frequencies, lefthanded materials with both negative effective permittivity and permeability may be synthesized in the optical domain with potential applications for imaging and nano-optics applications.Comment: 11 pages, 6 figures; modified the format, added a figur

Comparison of different methods of temporomandibular joint disc reconstruction - An animal model

The document attached has been archived with permission from the Australian Dental Association. An external link to the publisher’s copy is included. Article first published online: 12 MAR 2008The optimum method of temporomandibular joint (TMJ) reconstruction has not been defined despite numerous surgical treatments and several well controlled clinical trials. Animal models offer an experimental method allowing direct comparison of standardized surgical techniques. Advanced osteoarthrosis was induced bilaterally in 12 mature merino sheep. Three months later unilateral surgical reconstruction was performed. Four sheep had discectomy alone, four discectomy with fresh TMJ disc grafts, and four discectomy with fresh auricular grafts. All three surgical methods resulted in some reversal and repair of the osteoarthritic process, with the best result being from the auricular graft, next discectomy alone, next the disc graft, with the untreated osteoarthritic joint showing the most advanced pathosis. This study supports the role of surgical reconstruction in advanced degenerative disease of the temporomandibular joint, in particular, auricular graft reconstruction.Nobumi Ogi, Jun-Ichi Ishimaru, Kenichi Kurita, Yujiro Handa, Robert H.B. Jones, Alastair N. Gos

Spectral Dependence of Coherent Backscattering of Light in a Narrow-Resonance Atomic System

We report a combined theoretical and experimental study of the spectral and polarization dependence of near resonant radiation coherently backscattered from an ultracold gas of 85Rb atoms. Measurements in an approximately 6 MHz range about the 5s^{2}S_{1/2}- 5p^{2}P_{3/2}, F=3 - F'=4 hyperfine transition are compared with simulations based on a realistic model of the experimental atomic density distribution. In the simulations, the influence of heating of the atoms in the vapor, magnetization of the vapor, finite spectral bandwidth, and other nonresonant hyperfine transitions are considered. Good agreement is found between the simulations and measurements.Comment: 10 pages, 12 figur

Intermediate Element Abundances in Galaxy Clusters

We present the average abundances of the intermediate elements obtained by performing a stacked analysis of all the galaxy clusters in the archive of the X-ray telescope ASCA. We determine the abundances of Fe, Si, S, and Ni as a function of cluster temperature (mass) from 1--10 keV, and place strong upper limits on the abundances of Ca and Ar. In general, Si and Ni are overabundant with respect to Fe, while Ar and Ca are very underabundant. The discrepancy between the abundances of Si, S, Ar, and Ca indicate that the alpha-elements do not behave homogeneously as a single group. We show that the abundances of the most well-determined elements Fe, Si, and S in conjunction with recent theoretical supernovae yields do not give a consistent solution for the fraction of material produced by Type Ia and Type II supernovae at any temperature or mass. The general trend is for higher temperature clusters to have more of their metals produced in Type II supernovae than in Type Ias. The inconsistency of our results with abundances in the Milky Way indicate that spiral galaxies are not the dominant metal contributors to the intracluster medium (ICM). The pattern of elemental abundances requires an additional source of metals beyond standard SNIa and SNII enrichment. The properties of this new source are well matched to those of Type II supernovae with very massive, metal-poor progenitor stars. These results are consistent with a significant fraction of the ICM metals produced by an early generation of population III stars.Comment: 18 pages, 11 figures, 7 tables. Submitted to Ap

Iron Abundance Profiles of 12 Clusters of Galaxies Observed With BeppoSAX

We have derived azimuthally-averaged radial iron abundance profiles of the X-ray gas contained within 12 clusters of galaxies with redshift 0.03 < z < 0.2 observed with BeppoSAX. We find evidence for a negative metal abundance gradient in most of the clusters, particularly significant in clusters that possess cooling flows. The composite profile from the 12 clusters resembles that of cluster simulations of Metzler & Evrard (1997). This abundance gradient could be the result of the spatial distribution of gas-losing galaxies within the cluster being more centrally condensed than the primordial hot gas. Both inside and outside the core region, we find a higher abundance in cooling flow clusters than in non-cooling flow clusters. Outside of the cooling region this difference cannot be the result of more efficient sputtering of metals into the gaseous phase in cooling flow clusters, but might be the result of the mixing of low metallicity gas from the outer regions of the cluster during a merger.Comment: 8 pages, 2 embedded Postscript figures, accepted by Astrophysical Journa