X-ray Diagnostics of Thermal Conditions of the Hot Plasmas in the Centaurus Cluster

X-ray data of the Centaurus cluster, obtained with {\it XMM-Newton} for 45 ksec, were analyzed. Deprojected EPIC spectra from concentric thin shell regions were reproduced equally well by a single-phase plasma emission model, or by a two-phase model developed by {\it ASCA}, both incorporating cool (1.7--2.0 keV) and hot ($\sim 4$ keV) plasma temperatures. However, EPIC spectra with higher statistics, accumulated over 3-dimentional thick shell regions, were reproduced better by the two-phase model than by the singe-phase one. Therefore, hot and cool plasma phases are inferred to co-exist in the cluster core region within $\sim 70$ kpc. The iron and silicon abundances of the plasma were reconfirmed to increase significantly towards the center, while that of oxygen was consistent with being radially constant. The implied non-solar abundance ratios explains away the previously reported excess X-ray absorption from the central region. Although an additional cool ($\sim 0.7$ keV) emission was detected within $\sim 20$ kpc of the center, the RGS data gave tight upper limits on any emission with a tempeartures below $\sim 0.5$ keV. These results are compiled into a magnetosphere model, which interprets the cool phase as confined within closed magnetic loops anchored to the cD galaxy. When combined with so-called Rosner-Tucker-Vaiana mechanism which applies to solar coronae, this model can potentially explain basic properties of the cool phase, including its temperature and thermal stability.Comment: 53 pages, 11 figures, accepted for publication in Astrophysical Journa

Optical Hall Effect in the Integer Quantum Hall Regime

Optical Hall conductivity $\sigma_{xy}(\omega)$ is measured from the Faraday rotation for a GaAs/AlGaAs heterojunction quantum Hall system in the terahertz frequency regime. The Faraday rotation angle ($\sim$ fine structure constant $\sim$ mrad) is found to significantly deviate from the Drude-like behavior to exhibit a plateau-like structure around the Landau-level filling $\nu=2$. The result, which fits with the behavior expected from the carrier localization effect in the ac regime, indicates that the plateau structure, although not quantized, still exists in the terahertz regime.Comment: 4 pages, 4 figure

A possible route to spontaneous reduction of the heat conductivity by a temperature gradient driven instability in electron-ion plasmas

We have shown that there exists low-frequency growing modes driven by a global temperature gradient in electron and ion plasmas, by linear perturbation analysis within the frame work of plasma Kinetic theory. The driving force of the instability is the local deviation of the distribution function from the Maxwell-Boltzmann due to global temperature gradient. Application to the intracluster medium shows that scattering of the particles due to waves excited by the instability is possible to reduce mean free paths of electron and ion down to five to seven order of magnitude than the mean free paths due to Coulomb collisions. This may provide a hint to explain why hot and cool gas can co-exist in the intracluster medium in spite of the very short evaporation time scale due to thermal conduction if the conductivity is the classical Spitzer value. Our results suggest that the realization of the global thermal equilibrium is postponed by the local instability which is induced for quicker realization of local thermal equilibrium state in plasmas. The instability provides a new possibility to create and grow cosmic magnetic fields without any seed magnetic field.Comment: Accepted for publication in ApJ: 16 pages, 1figur

On the Flux-Across-Surfaces Theorem

The quantum probability flux of a particle integrated over time and a distant surface gives the probability for the particle crossing that surface at some time. We prove the free Flux-Across-Surfaces Theorem, which was conjectured by Combes, Newton and Shtokhamer, and which relates the integrated quantum flux to the usual quantum mechanical formula for the cross section. The integrated quantum flux is equal to the probability of outward crossings of surfaces by Bohmian trajectories in the scattering regime.Comment: 13 pages, latex, 1 figure, very minor revisions, to appear in Letters in Mathematical Physics, Vol. 38, Nr.

Highly Frequent Mutations in Negative Regulators of Multiple Virulence Genes in Group A Streptococcal Toxic Shock Syndrome Isolates

Streptococcal toxic shock syndrome (STSS) is a severe invasive infection characterized by the sudden onset of shock and multiorgan failure; it has a high mortality rate. Although a number of studies have attempted to determine the crucial factors behind the onset of STSS, the responsible genes in group A Streptococcus have not been clarified. We previously reported that mutations of csrS/csrR genes, a two-component negative regulator system for multiple virulence genes of Streptococcus pyogenes, are found among the isolates from STSS patients. In the present study, mutations of another negative regulator, rgg, were also found in clinical isolates of STSS patients. The rgg mutants from STSS clinical isolates enhanced lethality and impaired various organs in the mouse models, similar to the csrS mutants, and precluded their being killed by human neutrophils, mainly due to an overproduction of SLO. When we assessed the mutation frequency of csrS, csrR, and rgg genes among S. pyogenes isolates from STSS (164 isolates) and non-invasive infections (59 isolates), 57.3% of the STSS isolates had mutations of one or more genes among three genes, while isolates from patients with non-invasive disease had significantly fewer mutations in these genes (1.7%). The results of the present study suggest that mutations in the negative regulators csrS/csrR and rgg of S. pyogenes are crucial factors in the pathogenesis of STSS, as they lead to the overproduction of multiple virulence factors

Electrically driven spin excitation in a ferroelectric magnet DyMnO_3

Temperature (5--250 K) and magnetic field (0--70 kOe) variations of the low-energy (1--10 meV) electrodynamics of spin excitations have been investigated for a complete set of light-polarization configurations for a ferroelectric magnet DyMnO$_3$ by using terahertz time-domain spectroscopy. We identify the pronounced absorption continuum (1--8 meV) with a peak feature around 2 meV, which is electric-dipole active only for the light $E$-vector along the a-axis. This absorption band grows in intensity with lowering temperature from the spin-collinear paraelectric phase above the ferroelectric transition, but is independent of the orientation of spiral spin plane ($bc$ or $ab$), as shown on the original $P_{\rm s}$ (ferroelectric polarization) $\parallel c$ phase as well as the magnetic field induced $P_{\rm s}\parallel a$ phase. The possible origin of this electric-dipole active band is argued in terms of the large fluctuations of spins and spin-current.Comment: New version, 11 pages including colored 8 figure