Comment on "X-ray resonant scattering studies of orbital and charge ordering in Pr1-xCaxMnO3"

In a recent published paper [Phys. Rev. B 64, 195133 (2001)], Zimmermann et al. present a systematic x-ray scattering study of charge and orbital ordering phenomena in the Pr1-xCaxMnO3 series with x= 0.25, 0.4 and 0.5. They propose that for Ca concentrations x=0.4 and 0.5, the appearance of (0, k+1/2, 0) reflections are originated by the orbital ordering of the eg electrons in the a-b plane while the (0, 2k+1, 0) reflections are due to the charge ordering among the Mn3+ and Mn4+ ions. Moreover, for small Ca concentrations (x<0.3), the orbital ordering is only considered and it occurs at (0, k, 0) reflections. A rigorous analysis of all these resonance reflections will show the inadequacy of the charge-orbital model proposed to explain the experimental results. In addition, this charge-orbital model is highly inconsistent with the electronic balance. On the contrary, these reflections can be easily understood as arising from the anisotropy of charge distribution induced by the presence of local distortions, i.e. due to a structural phase transition.Comment: 10 pages, 2 figures.To be published Phys. Rev.

Polarization Dependence of Anomalous X-ray Scattering in Orbital Ordered Manganites

In order to determine types of the orbital ordering in manganites, we study theoretically the polarization dependence of the anomalous X-ray scattering which is caused by the anisotropy of the scattering factor. The general formulae of the scattering intensity in the experimental optical system is derived and the atomic scattering factor is calculated in the microscopic electronic model. By using the results, the X-ray scattering intensity in several types of the orbital ordering is numerically calculated as a function of azimuthal and analyzer angles.Comment: 9 pages, 7 figure

Relative contributions of lattice distortion and orbital ordering to resonant x-ray scattering in manganites

We investigated the origin of the energy splitting observed in the resonant x-ray scattering (RXS) in manganites. Using thin film samples with controlled lattice parameters and orbital states at a fixed orbital filling, we estimated that the contribution of the interatomic Coulomb interaction relative to the Jahn-Teller mechanism is insignificant and at most 0.27. This indicates that RXS probes mainly Jahn-Teller distortion in manganites.Comment: 8 pages, 4 figure

Monopole operators in three-dimensional N=4 SYM and mirror symmetry

We study non-abelian monopole operators in the infrared limit of three-dimensional SU(N_c) and N=4 SU(2) gauge theories. Using large N_f expansion and operator-state isomorphism of the resulting superconformal field theories, we construct monopole operators which are (anti-)chiral primaries and compute their charges under the global symmetries. Predictions of three-dimensional mirror symmetry for the quantum numbers of these monopole operators are verified.Comment: 23 pages, LaTex; v2: section 3.4 modified, section 3.5 extended, references adde

Pulmonary immune responses to Aspergillus fumigatus in an immunocompetent mouse model of repeated exposures

Aspergillus fumigatus is a filamentous fungus that produces abundant pigmented conidia. Several fungal components have been identified as virulence factors, including melanin; however, the impact of these factors in a repeated exposure model resembling natural environmental exposures remains unknown. This study examined the role of fungal melanin in the stimulation of pulmonary immune responses using immunocompetent BALB/c mice in a multiple exposure model. It compared conidia from wild-type A. fumigatus to two melanin mutants of the same strain, Δarp2 (tan) or Δalb1 (white). Mass spectrometry-based analysis of conidial extracts demonstrated that there was little difference in the protein fingerprint profiles between the three strains. Field emission scanning electron microscopy demonstrated that the immunologically inert Rodlet A layer remained intact in melanin-deficient conidia. Thus, the primary difference between the strains was the extent of melanization. Histopathology indicated that each A. fumigatus strain induced lung inflammation, regardless of the extent of melanization. In mice exposed to Δalb1 conidia, an increase in airway eosinophils and a decrease in neutrophils and CD8(+) IL-17(+) (Tc17) cells were observed. Additionally, it was shown that melanin mutant conidia were more rapidly cleared from the lungs than wild-type conidia. These data suggest that the presence of fungal melanin may modulate the pulmonary immune response in a mouse model of repeated exposures to A. fumigatus conidia

What lies beneath? The role of informal and hidden networks in the management of crises

Crisis management research traditionally focuses on the role of formal communication networks in the escalation and management of organisational crises. Here, we consider instead informal and unobservable networks. The paper explores how hidden informal exchanges can impact upon organisational decision-making and performance, particularly around inter-agency working, as knowledge distributed across organisations and shared between organisations is often shared through informal means and not captured effectively through the formal decision-making processes. Early warnings and weak signals about potential risks and crises are therefore often missed. We consider the implications of these dynamics in terms of crisis avoidance and crisis management

First Kepler results on compact pulsators II: KIC 010139564, a new pulsating subdwarf B (V361 Hya) star with an additional low-frequency mode

We present the discovery of nonradial pulsations in a hot subdwarf B star based on 30.5 days of nearly continuous time-series photometry using the \emph{Kepler} spacecraft. KIC 010139564 is found to be a short-period pulsator of the V361 Hya (EC 14026) class with more than 10 independent pulsation modes whose periods range from 130 to 190 seconds. It also shows one periodicity at a period of 3165 seconds. If this periodicity is a high order g-mode, then this star may be the hottest member of the hybrid DW Lyn stars. In addition to the resolved pulsation frequencies, additional periodic variations in the light curve suggest that a significant number of additional pulsation frequencies may be present. The long duration of the run, the extremely high duty cycle, and the well-behaved noise properties allow us to explore the stability of the periodic variations, and to place strong constraints on how many of them are independent stellar oscillation modes. We find that most of the identified periodicities are indeed stable in phase and amplitude, suggesting a rotation period of 2-3 weeks for this star, but further observations are needed to confirm this suspicion.Comment: 10 pages, accepted for publication in MNRA