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  • 1
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Materials Research 27 (1997), S. 585-623 
    ISSN: 0084-6600
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Rapid advances in the field of photorefractive polymers and composites have in the brief time since their inception in 1991 led to the development of high-performance materials with refractive index modulations approaching 0.01, dif-fraction efficiencies close to 100%, and net two-beam coupling gain coefficients exceeding 200 cm-1 in samples typically 100 mum thick. This paper reviews the current state of research, from the most successful synthetic strategies to produce polymeric photorefractive materials, to their emerging uses in applications. Two-beam coupling and four-wave mixing measurement techniques are presented and their importance in the characterization of the photorefractive properties of new materials is explained. The physics of the photorefractive effect in polymers is discussed with emphasis placed on the differences compared with the traditional inorganic photorefractive crystals. In particular, the orientational enhancement mechanism, which is believed to be responsible for the high performance of most of the low-glass-transition-temperature systems, is discussed in detail.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford UK : Blackwell Science Ltd.
    Journal of neurochemistry 74 (2000), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Exposure of rat cerebellar granule cells cultured to maturity in vitro to forskolin, N6,2′-O-dibutyryladenosine 3′,5′-cyclic monophosphate (Bt2cAMP), and 3-isobutyl-1-methylxanthine (IBMX) down-regulated GABAA receptor α6 and β3 subunits but up-regulated α1 and β2 subunits with respect to vehicle-treated controls. Dideoxyforskolin had no effect on subunit expression. Protein kinase A inhibitors, H-89 and Rp-adenosine 3′,5′-cyclic monophosphothioate, prevented these effects on α1 but not α6 subunit expression. Flunitrazepam-sensitive [3H]Ro 15-4513 binding sites were increased by 144 ± 20% following forskolin treatment. [3H]Ro 15-4513 photoaffinity labelling showed that the GABAA receptor α1 subunit was the principal locus of the increased flunitrazepam-sensitive [3H]Ro 15-4513 binding. Forskolin decreased flunitrazepam-insensitive [3H]Ro 15-4513 binding sites by 25 ± 8% and resulted in a 20% decrease in the irreversible incorporation of radioactivity in the α6 subunit. Steady-state levels of GABAA receptor subunit mRNAs were determined by semiquantitative RT-PCR in forskolin-treated cultures. Forskolin, Bt2cAMP, and IBMX down-regulated GABAA receptor α6 subunit mRNA expression; α1 and β3 mRNA levels were unaffected, whereas β2 subunit mRNA was up-regulated. Dideoxy-forskolin had no significant effect on α1, α6, β2, and β3 mRNA levels. Thus, in mature cerebellar granule cells, GABAA receptor expression can be regulated by intracellular cyclic AMP levels. This occurs at the level of gene transcription and/or translation by mechanisms that are only partially governed by protein kinase A.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 1515-1517 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A novel photorefractive polymer composite is reported which exhibits a high two-beam coupling gain coefficient (Γ=200 cm−1 at 120 V/μm, fast response time (τg=50 ms at 1 W/cm2), overmodulation of diffraction efficiency, and high sensitivity. The composition and processing have been altered to yield greatly improved material stability. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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