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  • 1
    ISSN: 1432-0649
    Keywords: PACS: 42.55.Rz
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. Yb:Ca4YO(BO3)3 (Yb:YCOB) crystal with good quality and large size has been grown by the Czochralski method. The polarization absorption and fluorescence spectra have been measured. The laser action of the Yb:YCOB crystal has been demonstrated when it is pumped by a fiber-coupled laser diode (LD) at the wavelength of 976.4 nm. The pumping threshold is 55 mW, the light-light conversion efficiency is 58.7%, and a slope efficiency of up to 73% is thus calculated.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Der Ophthalmologe 93 (1996), S. 549-551 
    ISSN: 1433-0423
    Keywords: Schlüsselwörter: Kontaktglas ; Tonometrie ; Durchblutung des Auges ; Beobachtung des Augenhintergrunds ; Key words: Contact lens ; Tonometry ; Hemodynamics ; Ocular pressure ; Observation of fundus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: This paper present a tonometer incorporated in a contact lens, which allows simultaneous measurement of intraocular pressure and performance ophthalmoscopy. The tonometer can record the pulse curve continuously, which can give us an indication of any circulatory problem. The device is therefore expected to yield additional information useful for the diagnosis of early glaucoma. Te device has three force sensors built in, which allow continuous measurement of the force exerted on the eye surface by the contact lens. The force of the contact lens on the eye can be altered and makes the adjustment of different eye pressures possible. These induced changes of the eye pressure and their influence on the fundus can be checked. We have taken some measurements on enucleated human eyes to compare our device with a Statham tansducer in the vitreous. We found a good correlation. We are currently taking measurements in volunteers. The clinical relevance of these observations and measurements will be examined in a future study.
    Notes: Nachdem bereits Ansätze zur kontinuierlichen Augendruckmessung bestehen, ist es nun gelungen, in einem Kontaktglas ein Tonometer einzubauen, bei welchem die Fundusspiegelung gleichzeitig mit der Druckmessung möglich ist. Über ebenfalls im Gerät integrierte Kraftsensoren kann die Auflagekraft des Kontaktglases auf dem Auge laufend gemessen werden. Durch Variiern der Kraft können verschiedene Augendrücke eingestellt und die dadurch induzierten Veränderungen am Fundus untersucht werden. Da das Tonometer kontinuierlich auch die Pulskurve aufzeichnet, kann die Analyse der Pulskurvenform Hinweise auf die Durchblutungspathologie geben. Aus den Untersuchungen mit diesem Gerät erwartet man wichtige neue Erkenntnisse zur Früherkennung des Glaukoms. Vergleichende Messungen an enukleierten Menschenaugen wurden mit dem neuen Gerät und einem Statham-Transducer durchgeführt. Es zeigte sich dabei eine gute Übereinstimmung der Werte. Erste Messungen an Probanden werden z.Z. vorgenommen. Die klinische Relevanz der Beobachtungen und Messungen wird in nächster Zeit im Rahmen einer klinischen Studie geprüft.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1572-9982
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of low temperature physics 33 (1978), S. 551-576 
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Calculations have been performed on superconducting constrictions with hyperbolic geometry. Stationary Ginzburg-Landau equations are used, neglecting magneticfields. Emphasis is placed on the difference between two-and three -dimensional constrictions, which is related to the difference between uniform-thickness (UT) and variable-thickness (VT) superconducting microbridges. The width of the constriction w, normalized to the coherence length ξ is indicated by the parameter A (≃ w/2ξ). It is found that small (A 〈 0.1), three-dimensional constrictions and VT bridges have a sinusoidal current-phase relation, linear temperature dependence of the critical current I c, and an I cR product (Ris the normal state resistance) equal to the Ambegaokar-Baratoff expression for Josephson junctions near T c. Two-dimensional constrictions behave as if they consist of an inner core with junction properties, in series with the films on both sides. The core consists of the region within a coherence length from the center of the structure. This size is temperature dependent. The core shows a sinusoidal current-phase relation and IcR according to Ambegaokar and Baratoff. For the whole constriction neither the phase difference nor R is finite. Two-dimensional constrictions have linear temperature dependence only when they are extremely narrow (A 〈 0.001). In two-dimensionalbridges the order parameter is depressed cover a distance of approximately the coherence length; in small three-dimensional constrictions this distance is approximately equal to the width. In narrow constrictions (and short microbridges) the current is not homogeneously distributedover the cross section. The effect has been investigated that occurs when in three-dimensional constrictions the width w is not much larger than l 0, the electron mean free path in the basic material. To this purpose a Ginzburg-Landau equation is derived from the Zaitsev boundary conditions which is valid for continuously changing material parameters. The critical current is decreased, but the IcR product remains constant.The results of the calculations are compared with experimental results for superconducting microbridges.
    Type of Medium: Electronic Resource
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