Ferroelectricity in perovskite HoMnO3HoMnO_3 and YMnO3YMnO_3

Ferroelectricity is observed in orthorhombic $HoMnO_3$ and $YMnO_3$ at the magnetic lock-in transitions into an E-type structure or an incommensurate phase with a temperature independent wave vector, respectively. In $HoMnO_3$ the ferroelectric polarization strongly depends on the external magnetic field indicating the involvement of the rare earth moment order in this compound. The results are discussed within the framework of recent theoretical models, in particular the double exchange driven polar displacements predicted for E-type magnetic structures.Comment: 5 pages, 3 figure

Encoding and Multiplexing of 2D Images with Orbital Angular Momentum Beams and the Use for Multiview Color Displays.

The orthogonal nature of different orbital angular momentum modes enables information transmission in optical communications with increased bandwidth through mode division multiplexing. So far the related works have been focused on using orbital angular momentum modes to encode/decode and multiplex point-based on-axis signals for maximum data channel numbers and capacity. Whether orbital angular momentum modes can be utilized to encode/decode off-axis signals for multiplexing in two-dimensional space is of significant importance both fundamentally and practically for its enormous potential in increasing the channel information capacity. In this work, a direct use of orbital angular momentum modes to encode/decode and multiplex two-dimensional images is realized in a scalable multiview display architecture, which can be utilized for viewing three-dimensional images from different angles. The effect of off-axis encoding/decoding and the resultant crosstalk between multiplexed different two-dimensional views are studied. Based on which, a color display of good image quality with four independent views is demonstrated. The resolution of the decoded images is analyzed and the limitation of this approach discussed. Moreover, a spatially multiplexed data communication scheme is also proposed with such a two-dimensional encoding/decoding approach to significantly enhance the data transmission capacity in free space for future data communication needs.UK Engineering and Physical Sciences Research Council (EPSRC) for the support through the Platform Grant for Liquid Crystal Photonics (EP/F00897X/1) and the EPSRC Centre for Innovative Manufacturing in Ultra Precision (EP/I033491/1

Large Magneto-Dielectric Effects in Orthorhombic HoMnO3 and YMnO3

We have found a remarkable increase (up to 60 %) of the dielectric constant with the onset of magnetic order at 42 K in the metastable orthorhombic structures of YMnO3 and HoMnO3 that proves the existence of a strong magneto-dielectric coupling in the compounds. Magnetic, dielectric, and thermodynamic properties show distinct anomalies at the onset of the incommensurate magnetic order and thermal hysteresis effects are observed around the lock-in transition temperature at which the incommensurate magnetic order locks into a temperature independent wave vector. The orders of Mn3+ spins and Ho3+ moments both contribute to the magneto-dielectric coupling. A large magneto-dielectric effect was observed in HoMnO3 at low temperature where the dielectric constant can be tuned by an external magnetic field resulting in a decrease of up to 8 % at 7 Tesla. By comparing data for YMnO3 and HoMnO3 the contributions to the coupling between the dielectric response and Mn and Ho magnetic orders are separated.Comment: revised manuscrip

Transmission electron microscopy and x-ray diffraction investigation of the microstructure of nanoscale multilayer TiAlN/VN grown by unbalanced magnetron deposition

Cubic NaCl-B1 structured multilayer TiAlN/VN with a bi-layer thickness of approximately 3 nm and atomic ratios of (Ti+Al)/V = 0.98 to 1.15 and Ti/V = 0.55 to 0.61 were deposited by unbalanced magnetron sputtering at substrate bias voltages between -75 and -150 V. In this paper, detailed transmission electron microscopy and x-ray diffraction revealed pronounced microstructure changes depending on the bias. At the bias -75 V, TiAlN/VN followed a layer growth model led by a strong (110) texture to form a T-type structure in the Thornton structure model of thin films, which resulted in a rough growth front, dense columnar structure with inter-column voids, and low compressive stress of -3.8 GPa. At higher biases, the coatings showed a typical Type-II structure following the strain energy growth model, characterized by the columnar structure, void-free column boundaries, smooth surface, a predominant (111) texture, and high residual stresses between -8 and -11.5 GPa

Human Neutrophil Elastase Degrades SPLUNC1 and Impairs Airway Epithelial Defense against Bacteria

Background:Acute exacerbations of chronic obstructive pulmonary disease (AECOPD) are a significant cause of mortality of COPD patients, and pose a huge burden on healthcare. One of the major causes of AECOPD is airway bacterial (e.g. nontypeable Haemophilus influenzae [NTHi]) infection. However, the mechanisms underlying bacterial infections during AECOPD remain poorly understood. As neutrophilic inflammation including increased release of human neutrophil elastase (HNE) is a salient feature of AECOPD, we hypothesized that HNE impairs airway epithelial defense against NTHi by degrading airway epithelial host defense proteins such as short palate, lung, and nasal epithelium clone 1 (SPLUNC1).Methodology/Main Results:Recombinant human SPLUNC1 protein was incubated with HNE to confirm SPLUNC1 degradation by HNE. To determine if HNE-mediated impairment of host defense against NTHi was SPLUNC1-dependent, SPLUNC1 protein was added to HNE-treated primary normal human airway epithelial cells. The in vivo function of SPLUNC1 in NTHi defense was investigated by infecting SPLUNC1 knockout and wild-type mice intranasally with NTHi. We found that: (1) HNE directly increased NTHi load in human airway epithelial cells; (2) HNE degraded human SPLUNC1 protein; (3) Recombinant SPLUNC1 protein reduced NTHi levels in HNE-treated human airway epithelial cells; (4) NTHi levels in lungs of SPLUNC1 knockout mice were increased compared to wild-type mice; and (5) SPLUNC1 was reduced in lungs of COPD patients.Conclusions:Our findings suggest that SPLUNC1 degradation by neutrophil elastase may increase airway susceptibility to bacterial infections. SPLUNC1 therapy likely attenuates bacterial infections during AECOPD. © 2013 Jiang et al

A Critical Examination of Hypernova Remnant Candidates in M101. II. NGC 5471B

NGC 5471B has been suggested to contain a hypernova remnant because of its extraordinarily bright X-ray emission. To assess its true nature, we have obtained high-resolution images in continuum bands and nebular lines with the Hubble Space Telescope, and high-dispersion long-slit spectra with the Kitt Peak National Observatory 4-m echelle spectrograph. The images reveal three supernova remnant (SNR) candidates in the giant HII region NGC 5471, with the brightest one being the 77x60 pc shell in NGC 5471B. The Ha velocity profile of NGC 5471B can be decomposed into a narrow component (FWHM = 41 km/s) from the background HII region and a broad component (FWHM = 148 km/s) from the SNR shell. Using the brightness ratio of the broad to narrow components and the Ha flux measured from the WFPC2 Ha image, we derive an Ha luminosity of (1.4+-0.1)x10^39 ergs/s for the SNR shell. The [SII]6716,6731 doublet ratio of the broad velocity component is used to derive an electron density of ~700 cm^-3 in the SNR shell. The mass of the SNR shell is thus 4600+-500 Mo. With a \~330 km/s expansion velocity implied by the extreme velocity extent of the broad component, the kinetic energy of the SNR shell is determined to be 5x10^51 ergs. This requires an explosion energy greater than 10^52 ergs, which can be provided by one hypernova or multiple supernovae. Comparing to SNRs in nearby active star formation regions, the SNR shell in NGC 5471B appears truly unique and energetic. We conclude that the optical observations support the existence of a hypernova remnant in NGC 5471B.Comment: 27 pages, 9 figures, to appear in May 2002 issue of The Astronomical Journa

Detection of an X-ray Pulsar Wind Nebula and Tail in SNR N157B

We report Chandra X-ray observations of the supernova remnant N157B in the Large Magellanic Cloud, which are presented together with an archival HST optical image and a radio continuum map for comparison. This remnant contains the recently discovered 16 ms X-ray pulsar PSR J0537-6910, the most rapidly rotating young pulsar known. Using phase-resolved Chandra imaging, we pinpoint the location of the pulsar to within an uncertainty of less than 1 arcsec. PSR J0537-6910 is not detected in any other wavelength band. The X-ray observations resolve three distinct features: the pulsar itself, a surrounding compact wind nebula which is strongly elongated and a feature of large-scale diffuse emission trailing from the pulsar. This latter comet tail-shaped feature coexists with enhanced radio emission and is oriented nearly perpendicular to the major axis of the pulsar wind nebula. We propose the following scenario to explain these features. The bright, compact nebula is likely powered by a toroidal pulsar wind of relativistic particles which is partially confined by the ram-pressure from the supersonic motion of the pulsar. The particles, after being forced out from the compact nebula (the head of the ``comet''), are eventually dumped into a bubble (the tail), which is primarily responsible for the extended diffuse X-ray and radio emission. The ram-pressure confinement also allows a natural explanation for the observed X-ray luminosity of the compact nebula and for the unusually small X-ray to spin-down luminosity ratio, compared to similarly energetic pulsars. We estimate the pulsar wind Lorentz factor of N157B as about 4 times 10^6 (with an uncertainty of a factor about 2, consistent with that inferred from the modeling of the Crab Nebula.Comment: 15 pages plus 4 figures. The postscript file of the whole paper is available at http://xray.astro.umass.edu/wqd/papers/n157b/n157b.ps. accepted for publication in Ap

A Deep Chandra Observation of the Giant HII Region N11 I. X-ray Sources in the Field

A very sensitive X-ray investigation of the giant HII region N11 in the LMC was performed using the Chandra X-ray Observatory. The 300ks observation reveals X-ray sources with luminosities down to 10^32 erg/s, increasing by more than a factor of 5 the number of known point sources in the field. Amongst these detections are 13 massive stars (3 compact groups of massive stars, 9 O-stars and one early B-star) with log(Lx/Lbol)~-6.5 to -7, which may suggest that they are highly magnetic or colliding wind systems. On the other hand, the stacked signal for regions corresponding to undetected O-stars yields log(Lx/Lbol)~-7.3, i.e., an emission level comparable to similar Galactic stars despite the lower metallicity. Other point sources coincide with 11 foreground stars, 6 late-B/A stars in N11, and many background objects. This observation also uncovers the extent and detailed spatial properties of the soft, diffuse emission regions but the presence of some hotter plasma in their spectra suggests contamination by the unresolved stellar population.Comment: file including online material, accepted for publication by ApJ