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  • 1
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 67 (1996), S. 2089-2095 
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: We have developed a novel bistatic polarization-modulated nephelometer that probes a medium enabling in situ measurement of angle- and polarization-dependent light scattering through a planar interface. This is particularly important for media with a planar interface such as sea ice but also for media in which measurements at great distance or depth, e.g., the atmosphere, are desirable. The instrument sits directly and noninvasively on the planar surface of the scattering medium. Light from a laser beam is directed into the medium and the scattered light is detected by analyzer optics. The angle of both the laser and detector beams in the medium can be varied continuously. Alternating current polarimetry is used to obtain phase function and polarization information of the scattered light. Measurements from this instrument of scattering from monodisperse polystyrene (latex) spheres in the laboratory are in good qualitative agreement with the results of Mie calculations and measurements made with a conventional monostatic nephelometer. This instrument has also been used to make preliminary investigations of scattering in sea ice in Pt. Barrow, Alaska. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: The Advanced Light Source (ALS) is a synchrotron radiation facility based on a low-emittance, 1.5-GeV electron storage ring presently under construction at the Lawrence Berkeley Laboratory, U.S.A. Plans are under way to develop a polarized photon facility at the ALS, exploiting the natural polarization properties of the bend magnet synchrotron radiation. The radiation emitted in the plane of the storage ring is linearly polarized, while above and below the plane it is elliptically polarized. We will utilize these properties to obtain circularly polarized soft x rays. A participating research team (PRT A018) has been formed and is proceeding with the design of a high-resolution beamline in the soft x-ray energy region 100–1500 eV. Intense beams of monochromatic, tunable, pulsed, circularly polarized photons will become available. We will discuss the physical characteristics of this polarized soft x-ray source. New investigations in biology, materials science, physics, and chemistry will become accessible. Initial experiments using circularly polarized photons in the soft x-ray region are planned in the areas of differential scattering and absorption from chiral molecules and probing the electronic and magnetic properties of magnetic systems. This work was supported by the U.S. Department of Energy (DE-AC03-76SF00098).
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 4214-4221 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The polarization state of a beam of light is fully described by the four elements of the Stokes vector. How the Stokes vector is transformed upon scattering is described by the sixteen element Mueller scattering matrix. Polarized light scattering provides a useful tool to study macromolecular structure. In particular, measurements of Mueller matrix elements have been used to study chromosome structure; changes in these measured quantities can be used to monitor structure as a function of cell cycle. Such measurements done on helical structures can be compared to theoretical computations to determine the geometrical parameters describing the helix. The matrix elements that are most sensitive to the chiral parameters of the helix are largest when the wavelength of light is of the order of the pitch of the helix. Therefore, polarized light scattering measurements made on DNA plectonemic helices would provide the most information in the far ultraviolet (UV) and x-ray region. The Mueller matrix elements are calculated using the coupled dipole approximation in the orientation average at wavelengths in the visible, ultraviolet, and x-ray regions. Each base-pair of the idealized plectonemic helix is represented by a single dipole. A complex polarizability tensor is assigned to each dipole. Calculations are sensitive to the writhe and polarizability of the DNA molecule.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 146-157 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The first Born approximation is used to calculate all 16 Mueller scattering matrix elements for a single, continuous helix at any orientation with respect to the incoming light. The results are compared to those from a helix characterized by point-polarizable subunits using the Born approximation and the coupled-dipole approximation. The number of point-polarizable groups necessary to describe the helix is investigated by comparing the calculations using the continuous helix to those using the helix made of discrete subunits. It is found that for large helices, many subunits are necessary, so in these cases, the continuous model may be more applicable. Conditions for the necessity of including dipolar interactions are established as a function of the dielectric constant of the material.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    facet.materialart.
    Unbekannt
    Cambridge : Periodicals Archive Online (PAO)
    The Modern language review. 76:2 (1981:Apr.) 484 
    ISSN: 0026-7937
    Thema: Allgemeine und vergleichende Sprach- und Literaturwissenschaft. Indogermanistik. Außereuropäische Sprachen und Literaturen
    Notizen: REVIEWS
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 6
    facet.materialart.
    Unbekannt
    Cambridge : Periodicals Archive Online (PAO)
    The Modern language review. 76:2 (1981:Apr.) 485 
    ISSN: 0026-7937
    Thema: Allgemeine und vergleichende Sprach- und Literaturwissenschaft. Indogermanistik. Außereuropäische Sprachen und Literaturen
    Notizen: REVIEWS
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    [s.l.] : Nature Publishing Group
    Nature 303 (1983), S. 307-308 
    ISSN: 1476-4687
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Notizen: [Auszug] The observations were made in December 1980 and May 1981. A dual-mode, linearly polarized feed was used for the telescope, followed by a two-channel FET receiver whose outputs were combined so that the system responded to left-handed circularly polarized waves. A system noise temperature of 65 K ...
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Journal of materials science 31 (1996), S. 6251-6257 
    ISSN: 1573-4803
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract Nanocomposite materials based on silica aerogel hosts have been produced using chemical vapour infiltration/decomposition methods and characterized by X-ray diffraction and electron microscopy. Amorphous tungsten in SiO2 aerogel was formed by the decomposition of W(CO)6 at 250 °C. Alternatively, reaction of this material with sulphur at 700 °C produced needle-shaped WS2 crystals with lengths ranging from 25–230 nm. Reaction of the W/SiO2 composite with anhydrous NH3 formed crystals of δ-WN with diameters of 1–5 nm. Fe(CO)5 is readily absorbed into the silica aerogel, forming an amorphous iron oxide/SiO2 composite after slow oxidation in air. Treatment of this material with additional Fe(CO)5 produced an Fe3O4/SiO2 aerogel composite. Fe3O4 particle sizes were 20–55 nm. After additional heat treatment, this composite exhibited soft ferromagnetic behaviour with a coercivity of ∼170 Oe. Fe9S10 crystals with diameters of 30–90 nm were formed by the reaction of the amorphous iron oxide/SiO2 composite with H2S at 900 °C.
    Materialart: Digitale Medien
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