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  • Dynamic polarizability  (2)
  • Excipients  (2)
  • Friability  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Effect of crystal potential on dynamic polarizability of negative ions (1996)
    Springer
    Theoretical chemistry accounts 93 (1996), S. 177-189 
    Details
    ISSN: 1432-2234
    Keywords: Crystal potential ; Dynamic polarizability ; Absorption oscillator strength ; Halogen anion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary We combine a time-dependent approach with a crystal potential model to study environment-specific optical linear response of closed-shell ions within crystals under the influence of an external time-varying field. It is shown how the dynamic dipole polarizability of free halogen anions within the normal dispersion region is altered due to the crystal potentials felt by the anions in environments appropriate for different binary cubic ionic lattices. The pole-positions of the in-crystal anion polarizability are found to be consistent with the vacuum ultraviolet absorption edges of the corresponding alkali halides and to vary linearly with the lattice potentials at the anion sites in these salts. It is observed that the crystal potential induces quite a large enhancement in the anionic absorption oscillator strengths of these dipole transitions, thereby making these values conform well with those of the first excitonic absorptions in such crystals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01113351
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  • 2
    Electronic Resource
    Electronic Resource
    Calcium phosphates in pharmaceutical tableting (1993)
    Springer
    Pharmacy world & science 15 (1993), S. 105-115 
    Details
    ISSN: 1573-739X
    Keywords: Calcium phosphates ; Drug compounding ; Excipients ; Particle size ; Physics ; Powders ; Tablets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Ten commercially available calcium phosphates used for direct tableting were evaluated. The particle size distributions, powder properties, Sorption isotherms and pH values of aqueous slurries were compared. All samples showed good or at least sufficient flowability. Scanning electron micrographs illustrated the different kinds of manufacturing and gave hints on their expectable behaviour under compaction pressure. The sorption isotherms of identical chemical substances, which had been manufactured by different methods, differed strongly. This can be related to their specific surface areas. Most of the hydroxylapatites have large surface areas and can absorb up to more than 15% water at 93% relative humidity. Dibasic calcium phosphate dihydrate was non-hygroscopic and absorbed less than 1% water. With the exception of monobasic calcium phosphate monohydrate all calcium phosphates behaved quite neutral in water. Monobasic calcium phosphate monohydrate can be regarded as a solid acid. Although the calcium phosphates are usually stable substances, the role of crystal water in the case of dibasic calcium phosphate dihydrate and monobasic calcium phosphate monohydrate is problematic due to possible interactions with active ingredients.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02113938
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  • 3
    Electronic Resource
    Electronic Resource
    Calcium phosphates in pharmaceutical tableting (1993)
    Springer
    Pharmacy world & science 15 (1993), S. 116-122 
    Details
    ISSN: 1573-739X
    Keywords: Calcium phosphates ; Drug compounding ; Ejection force ; Excipients ; Friability ; Hecket plots ; Lubrication ; Particle size ; Powders ; Tablets ; Tensile strength
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstracts Ten calcium phosphates suitable for direct compression (dibasic calcium phosphate dihydrate, dibasic calcium phosphate anhydrous and hydroxylapatite) were investigated with respect to their compressional behaviour. Except for Di-Cafos A all products gave tablets with sufficient to good mechanical strength. Nevertheless, there were differences between the products. All tablets prepared from the different products showed a high friability. This seems to be a problem of the calcium phosphates in general. On the other hand, the influence of magnesium stearate on the mechanical strength of the tablets was negligible for all products investigated. Moreover, a considerable effect of the particle size on the tensile strength of the tablets was found. The ejection forces and residual pressures were high in general, but critical only in the case of hydroxylapatites. Heckel plots were used to differentiate between plastic deformation and brittle fracture of the particles. In the case of calcium phosphates the slope of the Heckel plots indicated the hardness of the particles rather than their deformation behaviour.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02113939
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of crystal potential on dynamic polarizability of negative ions (1996)
    Springer
    Theoretica chimica acta 93 (1996), S. 177-189 
    Details
    ISSN: 0040-5744
    Keywords: Key words: Crystal potential ; Dynamic polarizability ; Absorption oscillator strength ; Halogen anion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary.  We combine a time-dependent approach with a crystal potential model to study environment-specific optical linear response of closed-shell ions within crystals under the influence of an external time-varying field. It is shown how the dynamic dipole polarizability of free halogen anions within the normal dispersion region is altered due to the crystal potentials felt by the anions in environments appropriate for different binary cubic ionic lattices. The pole-positions of the in-crystal anion polarizability are found to be consistent with the vacuum ultraviolet absorption edges of the corresponding alkali halides and to vary linearly with the lattice potentials at the anion sites in these salts. It is observed that the crystal potential induces quite a large enhancement in the anionic absorption oscillator strengths of these dipole transitions, thereby making these values conform well with those of the first excitonic absorptions in such crystals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01113351
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
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