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  • 1975-1979  (5)
  • Thermodynamics  (3)
  • Computer analysis  (1)
  • Coronary heart disease  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 25 (1978), S. 209-216 
    ISSN: 1432-0827
    Keywords: Thermodynamics ; Kinetics ; Apatite ; Octacalcium phosphate ; Tricalcium phosphate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary A thermodynamic analysis has been made of the secondary transition stage in the spontaneous precipitation of calcium phosphate following the amorphous-crystalline transformation. The first formed crystalline material has a solubility similar to that of octacalcium phosphate (OCP) and the computed thermodynamic solubility product remains invariant in the pH range 7.00–8.60. The duration of the secondary stage is sensitive to pH and the transition appears to occur by hydrolysis of the first formed OCP-like phase to a more basic apatitic phase with a tricalcium phosphate (TCP) stoichiometry. The crystalline material at the end of this transition has an invariant solubility product, in the pH range 7.00 to 8.60, when the TCP-like molecular formula is assumed. Changes in the solution chemistry which accompany the solid-tosolid transitions are consistent with the above conclusions. The results of this study are also consistent with those of a previous study which suggest that the stability of the amorphous calcium phosphate phase is dependent upon the instability of the solution phase with respect to OCP formation.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 25 (1978), S. 59-68 
    ISSN: 1432-0827
    Keywords: Amorphous calcium phosphate ; Thermodynamics ; Apatite ; Octacalcium phosphate ; Tricalcium phosphate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary A thermodynamic analysis of the precipitation of amorphous calcium phosphate (ACP) and its transformation to crystalline apatite has been made. A nearly constant ion product, over a wide variety of conditions, was obtained for a tricalcium phosphate (TCP)-like phase suggesting that the molecular unit which governs the solubility of ACP may be similar in composition to TCP. The introduction of 10% acid phosphate into the formula for the TCP ion product improves the fit of experimental data and results in an invariant ion product. The stability of ACP in solution was found to be dependent upon its thermodynamic instability with respect to an octacalcium phosphate (OCP)-like phase. The dependence of the induction period for the amorphous to crystalline transformation upon the pH and the Ca/P ratio of the solution is best explained by the assumption that an OCP-like phase is initially nucleated on the surfaces of the ACP particles. The events that occur in the immediate post-transition period suggest the hydrolysis of this OCP-like material to an apatitic phase.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 27 (1979), S. 153-160 
    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
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  • 4
    ISSN: 1432-1440
    Keywords: Heart catheterisation ; Cath-lab-systems ; Computer analysis ; Haemodynamic studies ; Man-computer interaction ; Computer reliability ; Herzkatheteruntersuchung ; Herzkatheterlabor ; Computeranalyse ; Hämodynamik ; Mensch-Computer-Dialog ; Computer-Zuverlässigkeit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Das in Aachen entwickelte Computersystem für die on-line-Analyse von hämodynamischen Daten ermöglicht im Dialog mit dem Rechner die sofortige Auswertung von Ekg, Drücken und Kälte- bzw. Farbstoffverdünnungskurven. Das Vorgehen bei der Kurvenauswertung sowie die vom Computer angestellten Berechnungen der einzelnen hämodynamischen Parameter werden beschrieben. Bei der Gegenüberstellung der ärztlich-manuellen Auswertung der auf Papier registrierten Druckkurven und der Computerresultate zeigt das in der täglichen Routine seit Oktober 1974 eingesetzte System eine sehr gute Korrelation für die Wellenerkennung und Wellenvermessung. Auch bei Verwendung verschiedener in der Praxis üblicher, flüssigkeitsgefüllter Katheter und des Tip-Manometers bestätigt sich für die Druckregistrierung in den einzelnen Herzabschnitten, daß das Computersystem für alle verwendeten Kathetermaterialien eine zuverlässige Auswertung bringt. Die flexible Konzeption des Computerprogramms mit seiner schnellen Adaptation an neue Fragestellungen erlaubt seinen Einsatz nicht nur in der klinischen Routine sondern besonders bei der Bearbeitung wissenschaftlicher Probleme im Rahmen hämodynamischer Untersuchungen.
    Notes: Summary The computer-system for the on-line-analysis of hemodynamic data developed in Aachen enables the clinical user to perform the immediate on-line analysis of ECG, pressure-curves and thermo- or dye-dilution-curves in a dialog mode. The procedure of pressure analysis as well as the calculations by the computer for the individual haemodynamic parameters are described. The comparison of the medicalmanual evaluation of the pressure curves on paper-registration and the computer results of the same measurement shows a very good correlation for wave-recognitions and wave-measurements for this system, integrated in the daily routine since 24 months. As well in the application of various fluid-filled catheters used in praxis as in tip-manometers it could be proved for the pressure-analysis in the different positions of the heart, that the computer-system produces reliable evaluations for all catheter materials used. The flexible conception of the computer program with its fast adaption to new problems allows its use not only in the clinical routine, but also and especially in the handling of scientific questions in the frame-work of haemodynamic analysis.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular medicine 56 (1978), S. 351-354 
    ISSN: 1432-1440
    Keywords: Angiocardiography ; Left ventricle ; Premature ventricular contractions ; Coronary heart disease ; Videometry ; Angiokardiographie ; Linker Ventrikel ; Extrasystolen ; Koronare Herzkrankheit ; Videometrie
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Die Kontrastmitteldarstellung des linken Ventrikels im Rahmen der Herzkatheteruntersuchung hat große Bedeutung in der Beurteilung der Dynamik des Myokards und der Herzklappen. Die Injektion von Kontrastmittel in den linken Ventrikel führt häufig zum Auftreten von Extrasystolen. Eine quantitative Analyse des Kontraktionsablaufs ist in diesen Fällen nicht möglich. Dieser Nachteil der Methode wird umgangen, wenn das Kontrastmittel in den rechten Vorhof injiziert wird. Die nach der Lungenpassage erzielte Darstellung des linken Ventrikels ist bei Anwendung der beschriebenen Technik frei von Extrasystolen und erfüllt die Kriterien der quantitativen Ventrikulographie. Die Erfahrungen der Arbeitsgruppe beruhen auf 57 Kontrastmitteldarstellungen des linken Ventrikels bei 32 Patienten mit verschiedenen Herzerkrankungen. Technik, Indikationen und spezielle Anwendungsmöglichkeiten (Videometrie, Druck/Volumen-Beziehung) werden dargestellt.
    Notes: Summary Left ventricular angiography as a diagnostic means is of considerable importance in the evaluation of myocardial and valvular dynamics. The injection of contrast medium into the left ventricle often causes premature ventricular contractions. In these cases quantitative analysis of the contraction pattern is impossible. This can be avoided by injection of the contrast medium into the right atrium. The technique described allows to obtain ventriculograms which meet the criteria for quantitative angiocardiography. 57 ventriculograms have been performed in 32 patients with various cardiac abnormalities. The study describes the technical procedure, the indications and limitations. Furthermore special applications are discussed (videometry, pressure-volume relationship).
    Type of Medium: Electronic Resource
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