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  • small-angle light scattering  (2)
  • Schlüsselwörter Frakturheilung • Knochenzement • Resorption  (1)
  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Der Orthopäde 26 (1997), S. 459-462 
    ISSN: 1433-0431
    Schlagwort(e): Key words Fracture healing • Bone cement • Degradation ; Schlüsselwörter Frakturheilung • Knochenzement • Resorption
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung In der Knochenbruchbehandlung werden Knochenzemente bei der Rekonstruktion von Kompressionsfrakturen, zur Auffüllung von Knochendefekten und für die Verbesserung der Verankerung von Implantaten im osteoporotischen Knochen eingesetzt. Da die Knochenzemente dabei nur eine temporäre Funktion haben, wären Zemente wünschenswert, die nach Abschluß der Knochenheilung abgebaut werden. Prinzipiell wird diese Anforderung von Kalziumphosphatzementen erfüllt, die durch verschiedene Forschergruppen in den letzten Jahren neu entwickelt wurden und in ihrem chemischen Aufbau dem Apatit im Knochen sehr ähnlich sind. Die Verarbeitungsbedingungen, die erreichten mechanischen Festigkeiten und die beobachteten Resorptionszeiten weisen zwischen den verschiedenen Produkten erhebliche Unterschiede auf. Klinische Langzeitstudien liegen bisher noch nicht vor. Ob diese neue Gruppe von Knochenzementen alle in sie gesetzten Erwartungen erfüllen kann, muß deshalb die Zukunft zeigen.
    Notizen: Summary Bone cements are used to treat compression fractures, fill bone defects and improve implant fixation in osteoporotic patients through reinforcement of weak bone. When the fracture repair is complete the bone cement ideally should degrade. In general, calcium-phosphate bone cements are biodegradable and can fulfill this temporary function. Several research groups have developed calcium-phosphate bone cements in the last years which have a chemical structure similar to that of the apatite of bone. However the conditions for processing the cement intraoperatively, as well as the mechanical properties and degradation characteristic of the various products show great variations. Clinical long-term studies have not yet been reported so far. Whether these new types of bone cements fulfill all the requirements for clinical application is still not certain and remains to be determined in future studies.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Rheologica acta 36 (1997), S. 1-12 
    ISSN: 1435-1528
    Schlagwort(e): Surfactant solution ; salt concentration ; shear-induced structure ; Cox-Merz rule ; small-angle light scattering
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Abstract We investigate the effect of excess salt and simple shear on the dynamics and structure of semi-dilute aqueous solutions of cetyltrimethylammonium bromide and sodium salicylate. Small-amplitude oscillatory rheological measurements suggest a structural evolution from an entangled to a multi-connected network as the salt concentration is increased. Steady-shear measurements, however, show a significant departure from the Cox-Merz rule. At low salt concentrations, this departure occurs at high shear rates with η* ∞ ω−0.92±0.08 and η ∞ γ−0.51±0.06 and is attributed to the formation of large shear-induced structures. The critical shear rate γ c at which the Cox-Merz rule fails approximates the inverse of the terminal relaxation time, τ. At high salt concentrations, however, the departure occurs at both low and high shear rates and is attributed to the formation of a multi-connected network. Small-angle light scattering (SALS) under shear was used to probe the mesoscopic structure and revealed novel scattering patterns exhibiting two-fold symmetry at low salt concentration and four-fold symmetry at high salt concentration. The SALS patterns were in qualitative agreement with the formation of large scale anisotropic structures at high shear rates and a multi-connected network at high salt concentrations.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Rheologica acta 36 (1997), S. 1-12 
    ISSN: 1435-1528
    Schlagwort(e): Key words Surfactant solution ; salt concentration ; shear-induced structure ; Cox-Merz rule ; small-angle light scattering
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Abstract We investigate the effect of excess salt and simple shear on the dynamics and structure of semidilute aqueous solutions of cetyltrimethylammonium bromide and sodium salicylate. Small-amplitude oscillatory rheological measurements suggest a structural evolution from an entangled to a multi-connected network as the salt concentration is increased. Steady-shear measurements, however, show a significant departure from the Cox-Merz rule. At low salt concentrations, this departure occurs at high shear rates with η*∝ω–0.92±0.08 and η∝˙γ–0.51±0.06 and is attributed to the formation of large shear-induced structures. The critical shear rate ˙γ c at which the Cox-Merz rule fails approximates the inverse of the terminal relaxation time, τ. At high salt concentrations, however, the departure occurs at both low and high shear rates and is attributed to the formation of a multi-connected network. Small-angle light scattering (SALS) under shear was used to probe the mesoscopic structure and revealed novel scattering patterns exhibiting two-fold symmetry at low salt concentration and four-fold symmetry at high salt concentration. The SALS patterns were in qualitative agreement with the formation of large scale anisotropic structures at high shear rates and a multi-connected network at high salt concentrations.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
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