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  • Articles: DFG German National Licenses  (4)
  • 1995-1999  (4)
  • density  (3)
  • Ablation  (1)
  • 1
    ISSN: 1434-3940
    Keywords: Schlüsselwörter CO2-Laser ; Scanner ; Ablation ; Ratten ; Histologie ; Key words CO2 laser ; Scanner ; Ablation ; Rats ; Histology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Introduction: Laser systems are frequently used in dentistry. New laser scanner technologies are promising more homogeneous ablation of pathological ablations of the skin and mucosa. The theoretical advantages of these systems have not yet been sufficiently evaluated by histological findings. For this reason, we compared two laser scanners with different scanning patterns in this study (Silktouch® and Swiftlase®, by Sharplan®, Germany). Materials and Methods: In this animal study (79 male Osborn-Mendel rats), skin defects of 3-mm diameter were lasered on to the backs of the animals, one for each method mentioned above (defocused laser, Swiftlase®, and Silktouch®). The histological investigations were conducted, depending on the time after surgery (9 h, 1, 2, 3, 4, 5, 6, 7, 9, 11, or 13 days). On the clinical site, we evaluated the visible ablation rate, homogeneity and morphology of the wound surface and the degree of carbonization. In the histomorphological investigations, we determined the degree of thermal damage as well as the morphology of the necrotic area and reepithelization pattern of the surface. Results: The Silktouch® scanner clinically showed a homogeneous ablation rate with less carbonization than the Swiftlase® scanner. In the histological specimen, this correlated with an increase in the tissue ablation rate and decreasing thermal damage to the surrounding tissue. Especially in the early wound-healing period, there was a more rapid reepithelization after the use of the Silktouch scanner. These differences could not be evaluated in the later wound-healing period. Compared to the defocused laser ablation, both scanning systems seem to have benefits within these parameters. Conclusions: The results of this study seem to show a diminished perifocal damage and reduced clinical postoperative morbidity achieved by using laser scanning systems. Compared to the Swiftlase® laser, the Silktouch® seems to deliver better results.
    Notes: Fragestellung: Lasersysteme finden in der Zahn-, Mund- und Kieferheilkunde zunehmend Anwendung. Laser-Scanner versprechen von ihrem methodischen Ansatz eine gleichmäßige Ablation von Haut- oder Schleimhautveränderungen, die theoretischen Vorteile derartiger Systeme sind aber bislang nicht ausreichend histologisch verifiziert. Daher wurden in dieser Studie 2 CO 2 -Laser-Scanner (Silktouch ® , Swiftlase ® ) unterschiedlicher Scanmuster diesbezüglich verglichen. Material und Methoden: In einem Tiermodell (79 Osborn-Mendel-Ratten) wurden je 3 mm große kutane Defekte durch CO 2 -Laser-Anwendung auf der Rückenhaut gesetzt. Die histologische Aufarbeitung erfolgte zu verschiedenen Zeitpunkten der Wundheilung. Klinische Zielparameter waren Ablationsrate, Homogenität und Morphologie der Wundoberfläche sowie das Ausmaß der Karbonisation. Die histologische Auswertung betrachtete das Ausmaß der Schädigung des Umgebungsgewebes sowie die Reepithelisierungsgeschwindigkeit der Oberfläche. Ergebnisse: Der Silktouch ® -Scanner zeigte klinisch eine gleichmäßigere Ablationsrate bei größerer Homogenität und verminderter Karbonisation als der Swiftlase ® -Scanner. Als histologisches Korrelat dieser klinischen Eigenschaften zeigte sich eine Steigerung des intendierten Gewebeabtrags bei gleichzeitig verminderter thermischer Schädigung des Umgebungsgewebes und exakt definierter lateraler Begrenzung der thermischen Schädigungszone. Insbesondere in der frühen Phase der Wundheilung zeigte sich eine beschleunigte Reepithelisierung nach Anwendung des Silktouch ® -Scanners. Diese Unterschiede waren in der Spätphase der Wundheilung kaum mehr nachweisbar. Im Vergleich zur defokussierten Gewebeablation zeigten beide Scanner deutliche Vorteile bezüglich der genannten Parameter. Schlußfolgerungen: Diese experimentellen Ergebnisse können als Hinweis auf eine Verminderung der perifokalen Schädigung mit reduzierter klinischer perioperativer Morbidität durch den Einsatz von Laserscannern gewertet werden. Im direkten Vergleich der beiden Scanner scheint der Silktouch ® günstigere Ergebnisse zu erzielen.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    International journal of thermophysics 16 (1995), S. 399-411 
    ISSN: 1572-9567
    Keywords: density ; high pressure ; high temperature ; magnetic suspension balance ; single-sinker densitometer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A new apparatus for density measurements of fluids in the entire range from gas to liquid densities is presented. The instrument is a single-sinker buoyancy densitometer designed in a completely new way. The buoyancy force exerted by the sample fluid on an immersed sinker (buoy) is transferred by a new type of magnetic suspension coupling to an analytical balance. In order to reduce drastically the linearity error of the (commercial) balance. a special basic load compensation is applied which also avoids any buoyancy ellèct of the laboratory air on the balance. The new single-sinker densitometer covers a density range from 10 to 200(1 kg - m ' at temperatures from 233 to 523 K and pressures up to 30 MPa. A special compact version of such a single-sinker densitometer can even he used at temperatures from 80 to 523 K at pressures up to 100 MPa. Test measurements on densities of carbon dioxide at 233, 360, and 523 K at pressures up to 30 MPa show that the estimated total uncertainty of ±0.02% to ±0.03% in density is clearly met.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1572-9567
    Keywords: combined viscosity/density measurement ; density ; magnetic suspension balance ; magnetic suspension coupling ; single-sinker densimeter ; viscometer ; viscosity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A new apparatus for measuring the viscosity and density of fluids is presented. The main element of the instrument is an electronically controlled magnetic suspension coupling. For the density measurement (buoyancy principle according to the single-sinker method), this coupling is used for the contactless transfer of the forces acting on a sinker in the measuring cell to an analytical balance. The coupling also serves as a frictionless bearing for a slender rotating cylindrical body which is slowed down due to the viscous drag of the fluid surrounding the cylinder. The viscosity of the fluid can be directly determined from the decay rate of the rotational frequency. The new combined viscometer-densimeter covers a viscosity range of 5 to 150 μPa·s and a density range from 20 to 2000 kg·m−3 at temperatures from 233 to 523 K and pressures up to 30 MPa. Test measurements on the viscosities and densities of nitrogen and carbon dioxide at 253, 293, and 523 K at pressures up to 30 MPa show an estimated total uncertainty of ±0.6 to ±1.0% in viscosity and of ±0.02 to ±0.05% in density.
    Type of Medium: Electronic Resource
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  • 4
    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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