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

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

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76800/1/AIAA-2004-3794-248.pd

Efficiency Analysis of a Hall Thruster Operating with Krypton and Xenon

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76277/1/AIAA-2005-3683-775.pd

Discharge Chamber Plasma Structure of a 40-cm NEXT-type Ion Engine

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76278/1/AIAA-2005-4250-941.pd

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

Internal Langmuir Probe Mapping of a Hall Thruster with Xenon and Krypton Propellant

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77012/1/AIAA-2006-4470-572.pd

Internal plasma potential measurements of a Hall thruster using xenon and krypton propellant

For krypton to become a realistic option for Hall thruster operation, it is necessary to understand the performance gap between xenon and krypton and what can be done to reduce it. A floating emissive probe is used with the Plasmadynamics and Electric Propulsion Laboratory’s High-speed Axial Reciprocating Probe system to map the internal plasma potential structure of the NASA-173Mv1 Hall thruster [R. R. Hofer, R. S. Jankovsky, and A. D. Gallimore, J. Propulsion Power 22, 721 (2006); and ibid.22, 732 (2006)] using xenon and krypton propellant. Measurements are taken for both propellants at discharge voltages of 500 and 600 V600V. Electron temperatures and electric fields are also reported. The acceleration zone and equipotential lines are found to be strongly linked to the magnetic-field lines. The electrostatic plasma lens of the NASA-173Mv1 Hall thruster strongly focuses the xenon ions toward the center of the discharge channel, whereas the krypton ions are defocused. Krypton is also found to have a longer acceleration zone than the xenon cases. These results explain the large beam divergence observed with krypton operation. Krypton and xenon have similar maximum electron temperatures and similar lengths of the high electron temperature zone, although the high electron temperature zone is located farther downstream in the krypton case.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87759/2/093502_1.pd