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  • 1
    Electronic Resource
    Electronic Resource
    A particle size distribution analysis of used HPLC column packing material (1993)
    Springer
    Chromatographia 35 (1993), S. 295-301 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Used column packings ; Particle size distribution ; Scanning electron microscopy ; Column age
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Particle size distribution analysis and scanning electron microscopy (SEM) were carried out on eight used HPLC columns containing either irregular silica based, spherical silica based or spherical polymer based packing material. Particle size distributions of the used irregular silica based columns were at least bimodat at the outlet ends and either biomodal or log-normal at the inlet ends with regular progressions between the two extremes through the column. A new ODS-3 column showed log-normal size distributions from the inlet to the outlet ends. Spherical silica based column particle size distributions showed distinct shoulders on large central distribution peaks in most column sections with various degrees of shoulder erosion. The spherical resin based column showed a broader inlet particle size distribution progressing to a very narrow outlet distribution. SEMs of both irregular and spherical silica based columns revealed a larger number of undersized particles and debris at the outlet than inlet ends which could have resulted from stationary phase degradation, since this was not seen in the new ODS-3 column. While several SEMs of the spherical silica based columns revealed hollow spheres and twins, the spherical resin based column packing showed stress fractures or wrinkle lines resulting from use or dehydration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02277513
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Breakdown of cytoplasmic vacuoles (1990)
    Springer
    Protoplasma 155 (1990), S. 144-152 
    Details
    ISSN: 1615-6102
    Keywords: Motile vacuoles ; Vesiculation ; Mathematical model ; Fixation ; Osmotic conditions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Plant cells possess an extensive motile vacuolar system (MVS) easily observed with dark field, Nomarski or phase contrast optics. The elements of the MVS are long cylindrical vacuoles, 1–6 μm in diameter, but are transformed into spherical vesicle upon fixation with non-coagulant fixatives (e.g., glutaraldehyde). A mathematical model is developed to describe the vesiculation event, taking into account osmotic properties of the fixing solution. A computer simulation is prepared, using the model equations, to examine response of vesicle radius and number under weak to strong osmotic conditions. Vesicle radius is strictly dependent upon initial vacuolar radius, while vesicle number is found to depend upon initial vacuole length as well as radius. However, vesicle number is more dependent upon initial vacuolar radius as osmotic influences increase. The model points out important basic properties of membrane cylinders and spheres that can be scaled up or down to include similar structures at various magnitudes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01322624
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    Paper (German National Licenses)
    Fulltext
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