Nasal fibrosis: long-term follow up of four cases of eosinophilic angiocentric fibrosis

Eosinophilic angiocentric fibrosis is a rare, benign cause of submucosal thickening and fibrosis within the upper respiratory tract. It predominantly affects the nose although cases have been reported in the subglottis. We describe four cases of the disease centred around the nasal cavity, with widespread infiltration of the facial soft tissues and orbit in three of the four patients. Each underwent long term follow up. Multiple surgical resections were required with two of our patients and, to date, medical therapy has been of limited help. The disease process, with its clinical and characteristic histopathological findings, is described. We also discuss the management of the disease following a comprehensive review of, and comparison with, the few prior reported cases

A direct image of the obscuring disk surrounding an active galactic nucleus

Active galactic nuclei (AGN) are generally accepted to be powered by the release of gravitational energy in a compact accretion disk surrounding a massive black hole. Such disks are also necessary to collimate powerful radio jets seen in some AGN. The unifying classification schemes for AGN further propose that differences in their appearance can be attributed to the opacity of the accreting material, which may obstruct our view of the central region of some systems. The popular model for the obscuring medium is a parsec-scale disk of dense molecular gas, although evidence for such disks has been mostly indirect, as their angular size is much smaller than the resolution of conventional telescopes. Here we report the first direct images of a pc-scale disk of ionised gas within the nucleus of NGC 1068, the archetype of obscured AGN. The disk is viewed nearly edge-on, and individual clouds within the ionised disk are opaque to high-energy radiation, consistent with the unifying classification scheme. In projection, the disk and AGN axes align, from which we infer that the ionised gas disk traces the outer regions of the long-sought inner accretion disk.Comment: 14 pages, LaTeX, PSfig, to appear in Nature. also available at http://hethp.mpe-garching.mpg.de/Preprint

VLBI Observations of NGC6240: resolving the double nuclei and radio supernovae

The European VLBI Network (EVN) has been used at two epochs in 2003 and 2009 to obtain multi-frequency high-resolution images of the merger galaxy NGC6240 in order to study the radio properties of all compact high-brightness components in the galaxy. Our observations at milli-arcsecond resolution detected the northern and southern nuclei and two radio components, which we interpret as long-lived luminous supernovae associated with the circum-nuclear starburst activity at the southern nucleus. The new VLBI data support the presence of an active galactic nucleus (AGN) together with starburst activity at the southern nucleus and provides some evidence for an AGN at the northern nucleus. The two nuclei both display an inverted spectrum at lower GHz frequencies. The spectrum of the southern nucleus indicates thermal free-free absorption on parsec scales, consistent with the presence of an AGN.Comment: 19 pages, 6 figures, accepted for publication in the Astronomical Journa

Discharge Chamber Plasma Structure of a 30-cm NSTAR-Type Ion Engine

Single Langmuir probe measurements are presented over a two-dimensional array of locations in the near Discharge Cathode Assembly (DCA) region of a 30-cm diameter ring cusp ion thruster over a range of thruster operating conditions encompassing the high-power half of the NASA throttling table. The Langmuir probe data were analyzed with two separate methods. All data were analyzed initially assuming an electron population consisting of Maxwellian electrons only. The on-axis data were then analyzed assuming both Maxwellian and primary electrons. Discharge plasma data taken with beam extraction exhibit a broadening of the higher electron temperature plume boundary compared to similar discharge conditions without beam extraction. The opposite effect is evident with the electron/ion number density as the data without began, extraction appears to be more collimated than the corresponding data with beam extraction. Primary electron energy and number densities are presented for one operating condition giving an order of magnitude of their value and the error associated with this calculation

A Flaring Megamaser in Mrk 348

We report new observations of the H2O megamaser in the Seyfert 2 galaxy Mrk 348. Following our initial detection in 2000 March using the Effelsberg 100 m telescope, re-analysis of previous data on this source indicates that the maser was present but only marginally detectable in late 1997. Monitoring through late 2000 shows that the maser has again decreased to its original level. The H2O line is redshifted by ~130 km/s with respect to the systemic velocity, is extremely broad, with a FWHM of 130 km/s, and has no detectable high velocity components within 1500 km/s on either side of the strong line. Followup VLBA observations show that the maser emission emanates entirely from a region >0.25 pc in extent, toward the base of the radio jet.Comment: 4 pages, 2 figures, to appear in Cosmic Masers: from Protostars to Black Holes, IAU 206, Eds. V. Migenes et al., ASP Conference Serie

Obscuring and feeding supermassive black holes with evolving nuclear star clusters

Recently, high resolution observations with the help of the near-infrared adaptive optics integral field spectrograph SINFONI at the VLT proved the existence of massive and young nuclear star clusters in the centres of a sample of Seyfert galaxies. With the help of high resolution hydrodynamical simulations with the PLUTO-code, we follow the evolution of such clusters, especially focusing on mass and energy feedback from young stars. This leads to a filamentary inflow of gas on large scales (tens of parsec), whereas a turbulent and very dense disc builds up on the parsec scale. Here, we concentrate on the long-term evolution of the nuclear disc in NGC 1068 with the help of an effective viscous disc model, using the mass input from the large scale simulations and accounting for star formation in the disc. This two-stage modelling enables us to connect the tens of parsec scale region (observable with SINFONI) with the parsec scale environment (MIDI observations). At the current age of the nuclear star cluster, our simulations predict disc sizes of the order of 0.8 to 0.9 pc, gas masses of 1.0e6 Msun and mass transfer rates through the inner boundary of 0.025 Msun/yr in good agreement with values derived from observations.Comment: 6 pages, 3 figures, to appear in the proceedings of the IAU General Assembly 2009, Rio de Janeiro, S267 Co-evolution of Central Black Holes and Galaxie

Internal plasma potential measurements of a Hall thruster using plasma lens focusing

Magnetic field topology has been found to be a central design concern for high-efficiency Hall thrusters. For future improvements in Hall thruster design, it is necessary to better understand the effects that magnetic field topology has on the internal plasma structure. The Plasmadynamics and Electric Propulsion Laboratory’s High-speed Axial Reciprocating Probe system is used in conjunction with a floating emissive probe to map the internal plasma potential structure of the NASA-173Mv1 Hall thruster [R. R. Hofer, R. S. Jankovsky, and A. D. Gallimore, J. Propul. Power 22, 721 (2006); 22, 732 (2006)]. Measurements are taken at 300 and 500 V500V with a xenon propellant. Electron temperature and electric field are also measured and reported. The acceleration zone and equipotential lines are found to be strongly linked to the magnetic field lines. Moreover, in some cases the ions are accelerated strongly toward the center of the discharge channel. The agreement between magnetic field lines and equipotential lines is best for high-voltage operation. These results have strong implications on the performance and lifetime optimization of Hall thrusters.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87754/2/103504_1.pd