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  • 2000-2004
  • 1975-1979  (2)
  • 1970-1974  (2)
  • 1900-1904
  • Current induced transition  (2)
  • Hydroxyapatite  (2)
  • 1
    Electronic Resource
    Electronic Resource
    A scanning electron microscopic study of the growth of hydroxyapatite crystals (1972)
    Springer
    Calcified tissue international 10 (1972), S. 91-102 
    Details
    ISSN: 1432-0827
    Keywords: Hydroxyapatite ; Calcification ; Phases ; Growth ; Microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé La croissance cristalline de l'hydroxyleapatite à 25° et à pH constant de 7.4 a été étudiée à l'aide du microscope électronique à balayage. La technique reproductible de croissance par ensemencement à partir de solutions stables sursaturées est utilisée efficacement pour produire des échantillons de minéral à divers stades distincts de croissance. Des changements de phase sont observés avec le progrès de la croissance; ils correspondent dans le temps avec les résultats cinétiques obtenus antérieurement. Un essai de rationalisation est tenté à la lumière des mécanismes proposés pour la formation d'hydroxyleapatite dans des conditionsin vivo.
    Abstract: Zusammenfassung Das Kristallwachstum von Hydroxyapatit bei 25° und einem konstanten pH von 7,4 wurde mit Hilfe eines Raster-Elektronenmikroskopes studiert. Die reproduzierbare Technik des Keimwachstums aus stabilen übersättigten Lösungen wurde mit Erfolg verwendet, um Mineralproben in verschiedenen bestimmten Stadien des Wachstums zu erhalten. Phasenveränderungen wurden beim fortschreitenden Wachstum beobachtet, und diese stimmten zeitlich gut überein mit kinetischen Resultaten, über welche früher berichtet wurde. Es wurde versucht, diese Beobachtungen zu erklären in Anbetracht von Mechanismen, welche für die Bildung von Hydroxyapatit unterin vivo-Bedingungen vorgeschlagen wurden.
    Notes: Abstract The crystal growth of hydroxyapatite at 25° and at a constant pH of 7.4 has been studied with the aid of a scanning electron microscope. The reproducible technique of seeded growth from stable supersaturated solutions was used effectively to produce samples of the mineral at various distinct stages of growth. Phase changes were observed as the growth proceeded and these corresponded favorably in time with kinetic results reported earlier. An attempt was made to rationalize the observations in light of mechanisms proposed for the formation of hydroxyapatite under conditions foundin vivo.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02012539
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Negative differential resistance in theV(I)-characteristic of superconducting Sn-whiskers (1975)
    Springer
    Applied physics 7 (1975), S. 127-130 
    Details
    ISSN: 1432-0630
    Keywords: Superconductivity ; Non-equilibrium transport properties ; Current induced transition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The current-induced step structure in the phase transition from the superconducting to the normal conducting state of whiskers of tin shows hysteretic behaviour. By shunting the whisker by a small normal conductor a stable reentrant part of theV(I)-characteristic (negative differential resistance) could be measured for the first step both by de and ac instruments. If the condition of stabilization is not fullfilled, the voltage in the hysteretic region shows oscillations. These oscillations were measured and calculated with a simple model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00884222
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Spannungsstufen in denU (T)-Übergangskurven undU (I)-Kennlinien stromtragender Zinn-Whisker (1973)
    Springer
    Applied physics 2 (1973), S. 303-320 
    Details
    ISSN: 1432-0630
    Keywords: Superconductivity ; Non-equilibrium transport properties ; Current induced transition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The current induced phase transition from the superconducting to the normalconducting state is studied in whiskers of tin. Transition curves were taken byU(T)-measurements at steady currents as well as characteristic curves byU (I)-measurements at fixed temperatures. For larger current intensities these curves show voltage steps which increase linearly with current intensity. The onset of voltage reading appears at the critical current density, as predicted by theory. The step structures are, however, observed at current densities which are several times larger than the critical ones. The influence of a magnetic field on the location and the structure of the curves was measured and is compared to theoretical predictions. At temperatures close toT co whiskers are onedimensional with respect to the superconducting orderparameter because of their small diameters. Therefore, intermediate state pattern and flux flow are rejected as an explanation of the observed structures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00896936
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Hydroxyl content of solution-precipitated calcium phosphates (1979)
    Springer
    Calcified tissue international 27 (1979), S. 153-160 
    Details
    ISSN: 1432-0827
    Keywords: Hydroxide ; Hydroxyapatite ; Titration ; Precipitation ; Thermodynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary A method is described for determination of the titratable hydroxide ion in calcium phosphate precipitates. The procedure requires accurate analysis of the other titratable species in the crystal lattice but is unaffected by the presence of other lattice constituents or impurities. The method was applied to precipitates that had been previously analyzed by solution thermodynamic techniques, and the results were consistent with the earlier observations. The hydroxide content of the precipitates increased with crystal maturity and with increasing pH of the precipitation medium. The hydroxide content of the amorphous phase and the immediate post-amorphous-crystalline transformation phase was shown to be nearly zero. After 3 to 4 days' maturation, the hydroxide content of precipitates prepared at pH values of 7, 8, and 9 was shown to increase to approximately 23, 40, 56% of that required for pure hydroxyapatite.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02441178
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    Paper (German National Licenses)
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