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  • Articles: DFG German National Licenses  (4)
  • 2000-2004  (2)
  • 1990-1994  (2)
  • 1915-1919
  • 2002  (2)
  • 1994  (2)
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  • Articles: DFG German National Licenses  (4)
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  • 2000-2004  (2)
  • 1990-1994  (2)
  • 1915-1919
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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5474-5488 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A theory is presented together with simulation results that describe three-dimensional position detection of a sphere located in a highly focused beam by back-focal plane interferometry. This technique exploits the interference of scattered and unscattered light, which is projected on a quadrant photodiode placed in the back-focal plane of a condenser lens. Due to the Gouy-phase shift inherent in focused beams, it is not only possible to determine the lateral but also the axial position of a spherical particle with nanometer accuracy. In this paper we describe the calculation of arbitrary focused electromagnetic fields, the Gouy phase shift, Mie scattering by focused beams and the resulting position signals using the angular momentum representation. The accuracy and the sensitivity of the detection system are investigated theoretically for various sphere parameters. Both accuracy and sensitivity depend on the incident light distribution as well as on the particle's properties and position. It is further shown that the maximum capture angle of the detection lens influences the detector's sensitivity in a nonlinear manner. Additionally, for optical trapping applications the influence of the laser power is taken into account and is considered through a noise analysis. For all investigated trapping conditions the reconstructed position deviates on average 〈1 nm laterally and 〈5 nm axially from the actual particle position. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 3367-3372 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A microscope using three water immersion objective lenses which realizes confocal, 4Pi-confocal and various confocal theta microscopies in fluorescence, transmission, scattered, and reflection mode is described. An argon-ion laser is the primary light source. A pulsed titanium-sapphire laser allows two-photon absorption fluorescence microscopy. The instrument has a predicted resolution of 100 nm along the illumination axis and a three-dimensional resolution of 5×106 nm3 for lenses each with a numerical aperture of 0.75. This is an improvement of an order of magnitude over a confocal fluorescence microscope using the same lens. Applications of the microscope range from observation of a sample at three different angles, to confocal theta fluorescence microscopy with multiphoton absorption. Since mounting and immersion media are identical, aberrations become negligible. The large working distance of 2 mm makes the instrument ideal for the observation of biological samples of up to 1.5 mm in diameter such as drosophila embryos.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 417 (2002), S. 806-807 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The two best-known physical limitations are Abbe's resolution limit in optical physics and Heisenberg's uncertainty principle in quantum physics. Each defines a natural limit to the resolution or accuracy with which certain parameters can be measured. But, writing in Physical Review Letters, Marcus ...
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    International journal of fracture 67 (1994), S. 151-167 
    ISSN: 1573-2673
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The single stress functions approach of Westergaard has often been conveniently used for a certain class of stress-prescribed crack problems. In the previous study, the Westergaard approach was successfully extended to displacement-prescribed crack problems. In this paper, the approach was further extended to the combined problem of displacement-prescribed cracks and stress-prescribed cracks. The method developed in the present paper simplifies the analysis of the mixed problem of interest. Several simple examples were discussed in detail to demonstrate the effectiveness of the method presented.
    Type of Medium: Electronic Resource
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