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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Optical and quantum electronics 31 (1999), S. 507-514 
    ISSN: 1572-817X
    Keywords: VIRGO mirrors ; wavefront control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The Franco-Italian VIRGO program to detect gravitational waves requires large mirrors whose optical properties are extremely severe: absorption and scattering 〈1ppm at 1064nm, wavefront homogeneity of 9nm RMS on Ø100mm. To achieve this performance on the wavefront, we have developed an experimental method to correct the wavefront shape to be as plane as possible. A thin silica layer is added through a mask by sputtering, where it is necessary on the surface, on the last layer of the multilayer. A phase retardation is produced. The wavefront is measured before and after correction with a Zygo interferometer. The first test has been done on Ø80mm mirror at 633nm. The wavefront peak to valley goes from 34 to 14nm. At this level, we are limited by the interferometer accuracy and repeatability. The optical property modifications due to the corrective coating are small (at 1064nm) or easy to overcome. The corrected wavefront includes at the moment the reference flat of the interferometer, so the measurements are not absolute. But the feasibility of this correction method is proved and it is powerful.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1433-0407
    Keywords: Schlüsselwörter Zentrale pontine Myelinolyse ; Extrapontine Myelinolysen ; Zerebrale Kernspintomographie ; Zerebrale Computertomographie ; Klinischer Verlauf ; Key words Central pontine myelinolysis ; Extrapontine myelinolyses ; Cerebral nuclear magnetic resonance tomography ; Cerebral computed tomography ; Clinical course
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Retrospective examination of 44 patients with central pontine and/or extrapontine myelinolysis leads to the conclusion that in early diagnostics cerebral NMR is superior to cCT. T2-weighted images turned out to be the most sensitive parameter. Frequent contrast-medium enhancement early in the course up to 4 weeks after clinical manifestation in 7 patients underlines the pathogenetic idea of an initial transient blood-brain barrier. According to our results, central-pontine myelinolysis (CPM) proof by NMR can be expected after 1 week. During the clinical course, cCT and NMR findings showed no regression. Also no connection was noted between the size of the pontine lesion and the favorable clinical course in 72.2% of the patients, nor was there a correlation with the extent of the neurological symptoms at the crisis of the disease. Altogether, cCT and NMR are irrelevant for the prognosis of cerebral myelinolysis.
    Notes: Zusammenfassung Die retrospektive Untersuchung an 44 Patienten mit zentralen pontinen und/oder extrapontinen Myelinolysen läßt den Schluß zu, daß die zerebrale MRT der CCT in der Frühdiagnostik überlegen ist, wobei sich die T2-Wichtung als sensibelster Parameter erwies. Das häufige KM-Enhancement gerade in der Frühphase bis zu 4 Wochen nach klinischer Manifestation bei 7 Patienten unterstrich die pathogenetische Vorstellung einer initialen transienten Blut-Hirn-Schrankenstörung. Bei entsprechendem klinischen Verdacht ist nach unseren Ergebnissen der ZPM-Nachweis in der MRT nach 1 Woche zu erwarten. Im Verlauf kam es nur zu einer tendenziellen Regredienz der CCT- und MRT-Befunde, wobei ein Zusammenhang zwischen pontiner Läsionsgröße und dem überwiegend bei 72,7% der Patienten günstigen klinischen Verlauf ebensowenig bestand wie eine Korrelation zum Ausmaß der neurologischen Symptomatik auf dem Höhepunkt der Erkrankung. Insgesamt haben somit zerebrale Computertomographie und zerebrale Kernspintomographie bei zerebralen Myelinolysen keinen Prognosewert.
    Type of Medium: Electronic Resource
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