The Experts below are selected from a list of 28797 Experts worldwide ranked by ideXlab platform
Bruce Macintosh - One of the best experts on this subject based on the ideXlab platform.
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Polarimetry with the gemini planet imager methods performance at first light and the circumstellar ring around hr 4796a
The Astrophysical Journal, 2015Co-Authors: Marshall D Perrin, G Duchene, Max Millarblanchaer, Michael P Fitzgerald, James R Graham, Sloane Wiktorowicz, Paul Kalas, Bruce MacintoshAbstract:We present the first results from the Polarimetry mode of the Gemini Planet Imager (GPI), which uses a new integral field Polarimetry architecture to provide high contrast linear Polarimetry with minimal systematic biases between the orthogonal polarizations. We describe the design, data reduction methods, and performance of Polarimetry with GPI. Point-spread function (PSF) subtraction via differential Polarimetry suppresses unpolarized starlight by a factor of over 100, and provides sensitivity to circumstellar dust reaching the photon noise limit for these observations. In the case of the circumstellar disk around HR 4796A, GPI's advanced adaptive optics system reveals the disk clearly even prior to PSF subtraction. In polarized light, the disk is seen all the way in to its semi-minor axis for the first time. The disk exhibits surprisingly strong asymmetry in polarized intensity, with the west side 9 times brighter than the east side despite the fact that the east side is slightly brighter in total intensity. Based on a synthesis of the total and polarized intensities, we now believe that the west side is closer to us, contrary to most prior interpretations. Forward scattering by relatively large silicate dust particles leads to the strong polarized intensity on the west side, and the ring must be slightly optically thick in order to explain the lower brightness in total intensity there. These findings suggest that the ring is geometrically narrow and dynamically cold, perhaps shepherded by larger bodies in the same manner as Saturn's F ring.
Hiroshi Ishikawa - One of the best experts on this subject based on the ideXlab platform.
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optical coherence tomography and scanning laser Polarimetry in normal ocular hypertensive and glaucomatous eyes
American Journal of Ophthalmology, 2000Co-Authors: Sek Tien Hoh, David S Greenfield, Andrea Mistlberger, Jeffrey M Liebmann, Hiroshi IshikawaAbstract:PURPOSE: To evaluate the relationship between visual function and retinal nerve fiber layer measurements obtained with scanning laser Polarimetry and optical coherence tomography in a masked, prospective trial. METHODS: Consecutive normal, ocular hypertensive, and glaucomatous subjects who met inclusion and exclusion criteria were evaluated. Complete ophthalmologic examination, disk photography, scanning laser Polarimetry, optical coherence tomography, and automated achromatic perimetry were performed. RESULTS: Seventy-eight eyes of 78 patients (17 normal, 23 ocular hypertensive, and 38 glaucomatous) were enrolled (mean age, 56.8 ± 11.5 years; range, 26 to 75 years). Eyes with glaucoma had significantly greater neural network scores on scanning laser Polarimetry and lower maximum modulation, ellipse modulation, and mean retinal nerve fiber layer thickness measured with optical coherence tomography compared with normal and ocular hypertensive eyes, respectively (all P < .005). Significant associations were observed between neural network number (r = −.51, r = .03), maximum modulation (r = .39, r = −.32), ellipse modulation (r = .36, r = −.28), and optical coherence tomography–generated retinal nerve fiber layer thickness (r = .68, r = −.59) and visual field mean deviation and corrected pattern standard deviation, respectively. All scanning laser Polarimetry parameters were significantly associated with optical coherence tomography–generated retinal nerve fiber layer thickness. CONCLUSION: Optical coherence tomography and scanning laser Polarimetry were capable of differentiating glaucomatous from nonglaucomatous populations in this cohort; however considerable measurement overlap was observed among normal, ocular hypertensive, and glaucomatous eyes. Retinal nerve fiber layer structural measurements demonstrated good correlation with visual function, and retinal nerve fiber layer thickness by optical coherence tomography correlated with retardation measurements by scanning laser Polarimetry.
K Lee - One of the best experts on this subject based on the ideXlab platform.
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scientific prospects for hard x ray Polarimetry
Astroparticle Physics, 2011Co-Authors: H Krawczynski, A Garson, Q Guo, M G Baring, P Ghosh, M Beilicke, K LeeAbstract:X-ray Polarimetry promises to give qualitatively new information about highenergy sources. Examples of interesting source classes are binary black hole systems, rotation and accretion powered neutron stars, Microquasars, Active Galactic Nuclei and Gamma-Ray Bursts. Furthermore, X-ray Polarimetry affords the possibility for testing fundamental physics, e.g. to observe signatures of light bending in the strong gravitational field of a black hole, to detect third order Quantum Electrodynamic effects in the magnetosphere of Magnetars, and to perform sensitive tests of Lorentz Invariance. In this paper we discuss scientific drivers of hard (>10 keV) X-ray Polarimetry emphasizing how observations in the hard band can complement observations at lower energies (0.1 - 10 keV). Subsequently, we describe four different technical realizations of hard X-ray polarimeters suitable for small to medium sized space borne missions, and study their performance in the signal-dominated case based on Monte Carlo simulations. We end with confronting the instrument requirements for accomplishing the science goals with the capabilities of the four polarimeters.
Sek Tien Hoh - One of the best experts on this subject based on the ideXlab platform.
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optical coherence tomography and scanning laser Polarimetry in normal ocular hypertensive and glaucomatous eyes
American Journal of Ophthalmology, 2000Co-Authors: Sek Tien Hoh, David S Greenfield, Andrea Mistlberger, Jeffrey M Liebmann, Hiroshi IshikawaAbstract:PURPOSE: To evaluate the relationship between visual function and retinal nerve fiber layer measurements obtained with scanning laser Polarimetry and optical coherence tomography in a masked, prospective trial. METHODS: Consecutive normal, ocular hypertensive, and glaucomatous subjects who met inclusion and exclusion criteria were evaluated. Complete ophthalmologic examination, disk photography, scanning laser Polarimetry, optical coherence tomography, and automated achromatic perimetry were performed. RESULTS: Seventy-eight eyes of 78 patients (17 normal, 23 ocular hypertensive, and 38 glaucomatous) were enrolled (mean age, 56.8 ± 11.5 years; range, 26 to 75 years). Eyes with glaucoma had significantly greater neural network scores on scanning laser Polarimetry and lower maximum modulation, ellipse modulation, and mean retinal nerve fiber layer thickness measured with optical coherence tomography compared with normal and ocular hypertensive eyes, respectively (all P < .005). Significant associations were observed between neural network number (r = −.51, r = .03), maximum modulation (r = .39, r = −.32), ellipse modulation (r = .36, r = −.28), and optical coherence tomography–generated retinal nerve fiber layer thickness (r = .68, r = −.59) and visual field mean deviation and corrected pattern standard deviation, respectively. All scanning laser Polarimetry parameters were significantly associated with optical coherence tomography–generated retinal nerve fiber layer thickness. CONCLUSION: Optical coherence tomography and scanning laser Polarimetry were capable of differentiating glaucomatous from nonglaucomatous populations in this cohort; however considerable measurement overlap was observed among normal, ocular hypertensive, and glaucomatous eyes. Retinal nerve fiber layer structural measurements demonstrated good correlation with visual function, and retinal nerve fiber layer thickness by optical coherence tomography correlated with retardation measurements by scanning laser Polarimetry.
Wolfgang-martin Boerner - One of the best experts on this subject based on the ideXlab platform.
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Contribution of Ernst Lüneburg to Mathematical and Optical Radar Polarimetry
2006Co-Authors: Wolfgang-martin Boerner, Andreas Danklmayer, Jorge J. MorisakiAbstract:On 2004 August 25, the geosciences and remote sensing community lost one of its principal applied mathematicians and electromagnetic fields experts in Dr. Ernst August Friedrich Luneburg. In his later years Ernst contributed profoundly towards arriving at a unified theory of radar and optical Polarimetry. Since he was well known and because he collaborated with several of us assembled here today during the IV International Workshop on Electromagnetic Wave Scattering at Gebze, Kocaeli, Turkey, it is proper to honor him here for his many contributions by this special memorial session for the advancement of multi-modal polarimetric SAR imaging and high resolution optical spectroscopy. It is the prime objective of this presentation to expand on the particular contributions of Dr. Ernst Luneburg exclusively to radar Polarimetry, which consists of three parts, (i) the eulogy focused on his contributions to optical and radar Polarimetry, (ii) the published contributions exclusively dealing with Polarimetry, and (iii) the memorial paper on a subject of considerable relevance to future developments of radar and SAR Polarimetry, interferometry and polarimetric SAR interferometry.
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Polarimetry in remote sensing: basic and applied concepts
IGARSS'97. 1997 IEEE International Geoscience and Remote Sensing Symposium Proceedings. Remote Sensing - A Scientific Vision for Sustainable Developme, 1997Co-Authors: Wolfgang-martin Boerner, H. Mott, E. LuneburgAbstract:One of the great challenges for modern radar is to classify, sort and identify targets of all kinds for military battlespace surveillance as well as for civilian geo-environmental stress change monitoring purposes. Whereas, in military radar utilization of complete polarization scattering matrix radars is not yet fully accepted, in remote sensing on the other hand, radar Polarimetry seems to have been accepted as an indispensable tool, and convincing results have been obtained for geo-environmental applications in agriculture, forestry, hydrology, flood plain and rural infrastructure maintenance, volcanology and seismology, archeology, etc. However, there still exists a large void in standardization and proper handling of basic and applied polarimetric theory and concepts. In this paper a succinct assessment of the current state-of-the-art is presented summarizing the basic Polarimetry concepts spelled out in Boerner et al. (1997). It is the purpose of this paper to draw attention of the IEEE Geoscience and Remote Sensing community to this recent compendium on 'Polarimetry in Remote Sensing'.
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Review and preview of wideband radar Polarimetry conferences, workshops, and symposia
Radar Polarimetry, 1993Co-Authors: Wolfgang-martin BoernerAbstract:A succint overview of basic events in the development of Polarimetry--low frequency to optical regions--is followed by a succinct summary of the basic underlying principles of 'Direct and Inverse Methods in Polarimetry', including some pertinent examples. A critical assessment of solved and unresolved problems is followed with a listing of recent workshops, providing the incentives for planning and executing a series of coordinated international meetings such as the SPIE, Radar Polarimetry Conference, San Diego, CA, 1992 July 23-24 the Second Polarimetric Radar Workshop, JIPR-2, Nantes, France, 1992 Sept 7-10, and the 'Wideband Imaging and Sensing Polarimetry: WISP', Adelaide, South Australia, 1992 August 14.
