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  • 1975-1979  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Diffraction efficiency and energy transfer during hologram formation in reduced KNbO3 (1979)
    Springer
    Applied physics 19 (1979), S. 153-163 
    Details
    ISSN: 1432-0630
    Keywords: 42.30.−d ; 42.40.−i ; 42.70.−a ; 72.40.tw ; 78.20.Jq
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Volume phase-hologram formation by the photorefractive effect in KNbO3 is accompanied by a stationary energy transfer between writing beams. The change in energy transfer by applying an electric field on the reduced crystals is shown to be due to an efficient increase in migration length which can reach values comparable or larger than the fringe spacing. It is demonstrated that photovoltaic contribution to the diffraction efficiency and energy transfer is rather small in reduced KNbO3 and that diffusion of photogenerated free holes is the dominant charge transport for the photorefractive effect in unbiased crystals. The experimental results for diffraction efficiency and energy transfer as a function of grating spacing, electric field, light intensity and temperature is well described by a recent theory of Kukhtarev and Vinetskii.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00932390
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  • 2
    Electronic Resource
    Electronic Resource
    Trimethoxyphenylverbindungen, VIII1) Borheterocyclen in der präparativen Naturstoffchemie; Synthese des Baeckeols2) (1976)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1976 (1976), S. 1514-1519 
    Details
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Trimethoxyphenyl Compounds, VIII. - Boron Heterocycles in Preparative Natural Products Chemistry; Synthesis of Baeckeol 2)2,4,6-Trimethoxytoluene, (CH3)zCH- (CH2) -CO2H ( n = 0 or 1 ) and boron trifluoride react, by selective demethylation, to give stable boron heterocycles and, by subsequent hydrolysis, baeckeol (2a) and homobaeckeol (2 b). 1,3,5-Trimethoxybenzene is acylated twice, but demethylation occurs only at one methoxy group.
    Notes: 2,4,6-Trimethoxytoluol gibt mit (CH3)2CH—(CH)n—CO2H (n = 0 oder 1) und Bortri- fluorid unter selektiver Entmethylierung stabile Borheterocyclen; deren Hydrolyse liefert Baeckeol (2a) sowie Homobaeckeol (2b). I,1,5-Trimethoxybenzo1 wild doppelt acyliert, aber nur einfach entmethyliert.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.197619760739
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Aromatische Phosphine mit Substituenten zweiter Ordnung, XV. Durch Phosphor aktivierte, nucleophile aromatische Substitution (1976)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1976 (1976), S. 2126-2135 
    Details
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Aromatic Phosphines with Second Order Substituents, XV. - Nucleophilic Aromatic Substitution Activated by PhosphorusIn hexamethylphosphoric triamide (HMPT) the halogen (particularly fluorine) of p-halogeno-phenylphosphines or (preferably) their oxides and sulfides can be replaced by R2N-, RNH-,HO-, NC-, and O2N-groups. The substitution hardly occurs in the meta-isomers thus demonstrating the mesomeric nature of the electron-withdrawing effect of phosphorus.
    Notes: In Hexamethylphosphorsäuretriamid (HMPT) läßt sich Halogen, vor allem Fluor, von p-Halogenphenylphosphinen oder (besser) ihren Oxiden und Sulfiden durch R2N-, RNH-,HO-, NC- und O2N-Gruppen ersetzen. Die Reaktion versagt weitgehend bei den meta-Isomeren und erweist so die mesomere Natur des Akzeptoreffektes des Phosphors.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.197619761119
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    Paper (German National Licenses)
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