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  • 1
    Electronic Resource
    Electronic Resource
    Single-mode fibers in fiber-optic quasielastic light scattering: A study of the dynamics of concentrated latex dispersions (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 6429-6443 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The concentration dependence (range 1–40 %) of the dynamics of monodisperse polymer latex dispersions (particle diameters 41–326 nm) is studied by fiber-optic quasielastic light scattering (FOQELS). The experiments reveal that despite the high turbidity of the samples multiple light scattering has negligible influence on the data when single-mode fibers are employed. This is explained by the diameter of the single-mode fiber core being much smaller than the scattering mean free paths in the dispersions. It is further shown that the autocorrelation functions can be interpreted in terms of the dynamic structure factor of the dispersions. When the particle diameter is raised from 41 to 326 nm the data show that FOQELS probes mutual diffusion for the smaller particles and self-diffusion for the larger ones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460272
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Culture conditions for induction of green plants from barley microspores by anther culture methods (1991)
    Springer
    Plant cell reports 9 (1991), S. 595-601 
    Details
    ISSN: 1432-203X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary With barley a large variation in frequency of plant formation from microspores of spikes from the same plant has been observed. The highest frequency of plant formation was obtained when culturing anthers in the dark on a high Ficoll medium containing 2,4-D and kinetin to induce proembryo (or callus) formation. Subsequently the proembryos or calli were cultured in dim light on a high Ficoll-high sugar medium containing IBA and kinetin. Finally the embryos were transferred to a starch agar medium. A maximum of 13 green plants were obtained from microspores of a single anther. The ratios of green to albino microspore derived plants varied from 9∶1 to 1∶9 depending on culture conditions. Under anaerobic conditions, lactic acid and other organic acids may have damaged the organelles in the cells resulting in the formation of albino plants. Thus, direct embryogenesis by using a well-buffered, high Ficoll-high sugar medium and proper aeration are essential for obtaining high frequency of green plants from microspores.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00231796
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Combination of temperature ramp with holographic relaxation spectroscopy for investigation of gelatin gels (1991)
    Springer
    Colloid & polymer science 269 (1991), S. 523-527 
    Details
    ISSN: 1435-1536
    Keywords: Holographic relaxation spectroscopy ; temperature ramp ; gelatin gels ; thermoreversible gels
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A new method of combining temperature ramp with holographic relaxation spectroscopy (TR-HRS) to investigate thermoreversible gels is reported. The gel melting temperature, gel content, and mobility of the gelatin molecules inside the gel networks can be simultaneously measured in one TR-HRS experiment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00655890
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Holographic relaxation spectroscopic study on the structure of gelatin gel doped with fluorescein as a tracer (1991)
    Springer
    Colloid & polymer science 269 (1991), S. 682-688 
    Details
    ISSN: 1435-1536
    Keywords: Gelatin gels, structure ; fluorescein ; translational diffusion ; holographic relaxation spectroscopy (HRS)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The structures of gelatin gels have been studied by holographic relaxation spectroscopy (HRS) with fluorescein as a doped tracer. An HRS spectrum with double peaks has been observed. It has been experimentally proven that this “anomalous” HRS spectrum is related to the structures of the gelatin gels. It is shown that two kinds of gel networks are formed when a gelatin solution is cooled at a rate of 2°C/min to a temperature below the gel temperature. Microviscosity inside one kind of network is about four times lower than inside the other one. One with lower microviscosity is called a “coarse” network, and it is formed through aggregation of a collagen-like, triple-stranded helix. The other is named a “fine” network and it is constructed simply by entanglements between polymer chains. The structure of gelatin gel can be considered as a blend of these two networks. By controlling the cooling speed, the structure of gelatin gels can be dominated by either “coarse” or “fine” gel networks.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00657405
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Diffusion in concentrated dispersions: a study with fiber-optic quasi-elastic light scattering (FOQELS) (1991)
    Springer
    Colloid & polymer science 269 (1991), S. 704-712 
    Details
    ISSN: 1435-1536
    Keywords: Dynamic light scattering ; fiber-optics ; latex ; dispersions ; self-diffusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A fiber-optic, quasi-elastic light-scattering instrument is described using single-mode fiber optical components, including a novel slanted exit face optode. The setup operates with homodyne signal detection. It enables the characterization of diffusion processes in concentrated dispersions up to volume concentrations of 50%. The performance of the instrument is exemplified with results obtained from latex spheres with diameters of 226 nm and 404 nm at volume fractions from Φ=0.01 to Φ=0.5. The correlation functions are analyzed according to the second order cumulants method and the “Contin”-procedure yielding an average and a distribution function of the short-time self-diffusion coefficient,D eff s , respectively. At high ionic strength the concentration dependence ofD eff s /D 0 is found to be in close agreement with theoretical predictions based on a multi-body interaction model of hard spheres up to Φ=0.45. With decreasing ionic strength the negative slope of the virial expansion tends to increase, presumably due to enhanced repulsive electrostatic interactions. The described technology offers new experimental means for on-line remote control sensing of particle size in concentrated disperse systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00657408
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    Paper (German National Licenses)
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