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  • 1995-1999  (3)
  • thermodynamic properties  (2)
  • Acoustic impedance tests  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Mund-, Kiefer- und Gesichtschirurgie 3 (1999), S. 12-16 
    ISSN: 1434-3940
    Keywords: Schlüsselwörter Gaumennahterweiterung ; Distraktionsosteogenese ; Osteotomie ; Atemwegsdiagnostik ; Reflexionsakustische Meßverfahren ; Key words Rapid palatal expansion ; Acoustic impedance tests ; Distraction osteogenesis ; Airway diagnosis ; Maxillary surgery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Objective: To investigate nasal airway changes through transverse maxillary distraction osteogenesis by means of an objective, reliable, non-invasive investigation technique with special attention to nasal valve changes and widening of the posterior maxilla. Patients and intervention: Eight patients with a severe maxillary transversal deficit underwent surgically assisted rapid palatal expansion in local or general anesthesia. Before and after the distraction process, a transnasal series of acoustic measurements of nasal airway profile was performed under topical decongestion. Nasal volume was calculated by integration of the area profile. The cross-sectional area of the nasal valve was also determined. Results: A significant enlargement of nasal volume was recorded in all patients (P 〈 0.01: Wilcoxon signed rank test). The average increase measured 5 cm3 (23%). The increase in volume was recorded in all parts of the nasal cavity, indicating complete maxillary expansion even in the posterior segment. The nasal valve area raised from 0.56 to 0.70 cm2 (P 〈 0.01). Six out of eight patients reported striking improvement of nasal patency after maxillary distraction. Conclusion: Besides correction of the maxillary arch deformity, rapid palatal expansion contributes to improved nasal patency by resolving nasal valve constriction. Significant widening of the posterior nasal cavity was achieved, indicating a translational pattern of maxillary movement, although the pterygomaxillary junction was not touched in the osteotomy.
    Notes: Fragestellung: In dieser Untersuchung sollten die Auswirkungen der transversalen Distraktion des Oberkiefers auf den nasalen Atemweg durch ein nichtinvasives Untersuchungsverfahren beschrieben werden. Es wird damit untersucht, ob die chirurgische Gaumennahterweiterung eine Weitung auch der posterioren Oberkieferbasis erreicht und durch Vergrößerung des Nasenklappenquerschnitts eine Normalisierung der nasalen Ventilation gelingen kann. Material und Methode: Bei 8 Patienten mit hochgradigem Schmalkiefer wurde eine transversale Distraktion des Oberkiefers vorgenommen. Vor der Osteotomie und nach Abschluß der Distraktion wurde das Querschnittprofil des nasalen Atemwegs unter lokaler Schleimhautabschwellung reflexionsakustisch bestimmt. Nasenvolumina und Querschnittsfläche der Nasenklappe wurden berechnet. Ergebnisse: Bei sämtlichen Patienten konnte eine signifikante Zunahme des Nasenvolumens nachgewiesen werden (p 〈 0,01: Wilcoxon-Paardifferenzentest), im Mittel vergrößerte sich das Nasenvolumen um 5 cm 3 . Die Weitung betraf gleichermaßen den vorderen, den mittleren und den hinteren Nasenabschnitt. Der Querschnitt der Nasenklappe vergrößerte sich signifikant (p 〈 0,01) von 0,56 cm 2 auf 0,7 cm 2 . 6 von 8 Patienten berichteten über eine deutliche subjektive Verbesserung der Nasenatmung. Schlußfolgerung: Neben der Weitung des Zahnbogens schafft die chirurgisch unterstütze Gaumennahterweiterung anatomische Voraussetzungen zur Verbesserung der Nasenatmung am ehesten durch eine Erweiterung der Nasenklappe. Auch ohne Osteotomie der Sutura pterygomaxillaris kann eine signifikante Vergrößerung des posterioren Nasenvolumens erreicht werden. Daher ist eine Translationskomponente des Segmenttransports anzunehmen.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    International journal of thermophysics 17 (1996), S. 391-404 
    ISSN: 1572-9567
    Keywords: coexistence curve ; equation of state ; Lennard Jones fluid ; thermodynamic properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A new equation of state (EOS) is proposed for the Helmholtz energyF of the Lennard Jones fluid which represents the thermodynamic properties over a wide range of temperatures and densities. The EOS is written in the form of a generalized van der Waals equation.F =F u +F v. WhereF u is a hard body contribution andF A an anttractive dispersion force contribution. The expression forF H is closely related to the hybrid Barker Henderson pertubation theory. The construction ofF A is accomplished with the Setzmann Wagner optimization procedure on the basis of virial coefficients and critically assessed computer simulation data. A comparison with the EOS of Johnson et al. shows improvement in the description of the vapor liquid coexistence properties, thepvT data. and in peculiar, of the calorie properties. A comparison with the EOS of Kolafa and Nezbeda which appeared after the bulk of this work was finished shows still by about 30%.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    International journal of thermophysics 19 (1998), S. 1121-1132 
    ISSN: 1572-9567
    Keywords: caloric properties ; density ; equation of state ; nitrogen ; thermodynamic properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A new formulation describing the thermodynamic properties of nitrogen has been developed. New data sets which have been used to improve the representation of the p–ρ–T surface of gaseous, liquid and supercritical nitrogen, including the saturated states are now available. New measurements on the speed of sound from spherical resonators have been used to improve the accuracy of caloric properties in gaseous and supercritical nitrogen. State-of-the-art algorithms for the optimization of the mathematical structure of the equation and special functional forms for an improved description of the critical region were used to represent even the most accurate data within their experimental uncertainty. The uncertainty in density of the new reference equation of state ranges from ±0.01% between 270 and 350 K at pressures less than 12MPa, within ±0.02% over all other temperatures less than 550 K and pressures less than 12 MPa, and up to a maximum of ±0.6% at the highest pressures. The equation is valid from the triple point to temperatures of 1000 K and pressures up to 2200 MPa. The new formulation yields a reasonable extrapolation up to the limits of chemical stability of nitrogen as indicated by comparison to experimental shock tube data. Constraints regarding the structure of the equation ensure reasonable extrapolated properties up to temperatures and pressures of 5000 K and 25 GPa. For typical calibration applications, the new reference equation is supplemented by a simple but also highly accurate formulation, valid only for supercritical nitrogen between 270 and 350 K at pressures up to 30 MPa.
    Type of Medium: Electronic Resource
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