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  • 1
    ISSN: 1432-1963
    Schlagwort(e): Schlüsselwörter Angeborene Herzfehler ; Fetale Autopsie ; Autopsiemethode ; Pränatale Diagnostik ; Keywords Congenital heart defects ; Fetal autopsy ; Autopsy method ; Prenatal diagnostics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Abstract As a result of the quality of prenatal ultrasound and the expanded experience of prenatal diagnosticians, it is possible to observe congenital heart malformations in increasingly greater detail and at an ever earlier stage of gestation [4]. Since it is on the basis of ultrasound findings that decisions to terminate pregnancies are made, it is of cardinal importance that after termination monitoring and confirmation of the prenatal diagnosis be carried out. This need can only be adequately met by autopsy. There are different methods for carrying out autopsies when there is suspicion of a congenital heart defect: a) the Anderson sequential segmental analysis as modified according to the Berlin method; b) use of a special autoptic method corresponding to the ultrasound findings, based on defining a preferred sectional plane; c) stereo-microscopically; or d) microscopically after embedding and preparation of serial microscopic sections. For the pathologist the consequence is that he has to adapt his autopsy method to the ultrasound findings and the age of the fetus. This enables him to determine an optimal, case-based autopsy strategy for each type of cardiac defect, which is essential for monitoring of the prenatal diagnosis. The present paper discusses the various autoptic methods used in cases of congenital heart malformations and the consequences for the pathologist of the continuing improvements in prenatal diagnostics.
    Notizen: Zusammenfassung Aufgrund der Qualität der Untersuchungsergebnisse des pränatalen Ultraschalls und der gestiegenen Erfahrungen in der Pränataldiagnostik, lassen sich angeborene Herzfehler detaillierter und in immer früheren Schwangerschaftswochen darstellen [4]. Da auf der Basis der Ultraschallbefunde Entscheidungen über die Beendigung von Schwangerschaften getroffen werden, besteht nach vollzogener Beendigung der Schwangerschaft, ein starkes Bedürfnis nach Kontrolle und Bestätigung der pränatalen Diagnostik. Dies kann erschöpfend nur durch die Sektion befriedigt werden. Angeborene Herzfehler können mit verschiedenen Methoden seziert werden: a) nach der Anderson-Segmentanalyse, modifiziert nach der Berliner-Methode, b) nach einer speziellen Sektionstechnik entsprechend der Ultraschallbefunde mit Festlegung einer pathologisch-anatomischen Vorzugsschnittebene, c) stereomikroskopisch oder d) mikroskopisch nach Einbettung und Aufarbeitung in Serienschnitten. Die Konsequenz, die sich daraus für den Pathologen ergibt ist, dass er seine Sektionstechnik in Abhängigkeit von Ultraschallbefund und Alter des Fetus anpassen und festlegen muss. Somit kann eine adäquate fallabhängige Autopsiestrategie für jeden speziellen Herzfehler festgelegt werden, die für die Qualitätskontrolle der pränatalen Diagnostik unerlässlich ist. In dem folgenden Beitrag werden verschiedene Sektionstechniken bei angeborenen Herzfehlern analysiert und die sich aus den derzeitigen Ergebnissen der pränatalen Diagnostik ableitenden Konsequenzen für Pathologen, dargestellt.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    International journal of thermophysics 12 (1991), S. 27-42 
    ISSN: 1572-9567
    Schlagwort(e): noble gases ; second transport virial coefficients ; thermal conductivity ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The usual procedure that the transport properties at atmospheric pressure are identified with values in the limit of zero density cannot be accepted for all reduced temperatures T *. It is shown in the framework of the Rainwater-Friend theory for noble gases, as a good example, that for T *〈1 the effect of the initial density dependence has different signs for viscosity and thermal conductivity and amounts to a few percent, when data at atmospheric pressure are compared with zero-density values. An improved representation of the monomer-dimer contribution to the second transport virial coefficients of the Rainwater-Friend theory is presented in the paper. This is based, among others, on the author's own experimental data of the initial density dependence of viscosity of polytomic gases.
    Materialart: Digitale Medien
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  • 3
    ISSN: 1572-9567
    Schlagwort(e): binary diffusion coefficient ; gas mixtures ; methanol-benzene ; methanol-cyclohexane ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The paper reports experimental results for the viscosity of the vapor mixtures methanol-benzene (five mole fractions with densities up to 1.5kg·m−3 and 0.022 mol·L −1) and methanol-cyclohexane (four mole fractions with densities up to 1.9kg·m−3 and 0.026 mol·L −1). In analogy to the pure components, the measurements on the mixtures were carried out with an oscillating-disk viscometer with small gaps, completely made of quartz, beginning as near as possible to room temperature and continuing to a maximum temperature of 630 K. A first evaluation by means of the Chapman-Enskog theory of dilute gases has shown differences in the resulting values of the interaction viscosity η ij (0) in the limit of zero density exceeding the experimental errors. Consistent results were obtained by taking into account the initial density dependence of the viscosity within the framework of the modified Enskog theory for gaseous mixtures. The values of η ij (0) were also used to estimate binary diffusion coefficients of the mixtures.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    International journal of thermophysics 13 (1992), S. 791-800 
    ISSN: 1572-9567
    Schlagwort(e): high pressure ; mesitylene ; mixtures ; toluene ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract New absolute measurements of the viscosity of mesitylene and binary mixtures of toluene + mesitylene are presented. The measurements were performed in a vibrating-wire instrument and cover a temperature range of 295–330 K and pressures up to 55 MPa. The concentrations studied were 40 and 70%, by weight, of toluene. The overall uncertainty in the reported data is estimated to be ±0.5%. A recently extended semiempirical scheme for the prediction of the viscosity of mixtures from the pure components is used to predict successfully the viscosity of these mixtures, as a function of composition, temperature, and pressure.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    International journal of thermophysics 16 (1995), S. 63-78 
    ISSN: 1572-9567
    Schlagwort(e): R134a ; dilute gas ; refrigerant ; saturation properties ; 1,1,1,2-tetrafluoroethane ; thermal conductivity ; transport properties ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The paper contains a status report on an international project coordinated by the Subcommittee on Transport Properties of Commission 1.2 of the International Union of Pure and Applied Chemistry. The project has been conducted to investigate the large discrepancies between the results reported by various authors for the transport properties of R134a. The project has involved the remeasurement of the transport properties of a single sample of R134a in nine laboratories throughout the world in order to test the hypothesis that at least part of the discrepancy could be attributed to the purity of the sample. This paper provides an intercomparison of the new experimental results obtained to data in this project for the viscosity and the thermal conductivity in both gaseous and liquid phases. The agreement between the viscosity data from the laboratories contributing to the project was improved with several techniques, now producing consistent results. This suggests that the purity of the samples of R134a used in previous work was at least partly reponsible for the discrepancies observed. For the thermal conductivity in the liquid phase the results of the measurements are also more consistent than before, although not for all experimental techniques. Not all of the previous measurements suffered from significant sample impurities, so the present measurements on a consistent high-purity sample can he used to detect data sets which are outhers, possibly because of impurities. Identification of laboratories and techniques with systematic differences may require the examination of data for several fluids. The implications for future measurements of the transport properties of other refrigerants are significant.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    International journal of thermophysics 12 (1991), S. 999-1012 
    ISSN: 1572-9567
    Schlagwort(e): collision cross section ; ethane ; polyatomic gas ; thermal conductivity ; transport properties ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract New representations of the viscosity and thermal conductivity of ethane in the limit of zero density are provided. The correlation for the viscosity extends over the temperature range 200 to 1000 K, whereas that for thermal conductivity extends from 225 to 725 K. The behavior of each property is represented by an independent correlation of the appropriate effective collision cross section as a function of temperature. The final results are compared with experimental data as well as with earlier correlations. The accuracy of the viscosity correlation is estimated to be ±0.5 % in the temperature range 300 K⩽T⩽600 K, increasing to ±1.5 and ±2.5% at 200 and 1000 K, respectively. The uncertainty associated with the thermal conductivity correlation is ±2 % in the temperature range 300 K⩽T⩽500 K, increasing to ±3% at either end. The results of this study indicate that there is an urgent need for additional high-precision measurements of thermal conductivity especially for temperatures above 400 K.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    International journal of thermophysics 14 (1993), S. 805-818 
    ISSN: 1572-9567
    Schlagwort(e): phenol ; second viscosity virial coefficient ; transport properties ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract New measurements of the vapor-phase viscosity of phenol were performed from 437 up to 624 K and for densities between 0.006 and 0.023 mol · L−1 in an all-quartz oscillating-disk viscometer with small gaps. Thus, including our own measurements reported earlier, experimental data are available in the temperature range between 376 and 639 K and in the density range from 0.001 up to 0.023 mol · L−1. The data were evaluated with a density series for the viscosity in which only a linear density contribution is included. The values of the second viscosity virial coefficient obtained for phenol as well as for benzene, toluene, and p-xylene were compared with results of the Rainwater-Friend theory and of the modified Enskog theory on the basis of the Lennard-Jones 12-6 potential. The agreement is reasonable, when the potential parameter ratios determined by Bich and Vogel are used. The influence of bound dimers seems to be already taken into account in the three-monomer contribution according to Hoffman and Curtiss.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    International journal of thermophysics 16 (1995), S. 1245-1255 
    ISSN: 1572-9567
    Schlagwort(e): binary gaseous mixture ; carbon dioxide ; ethane ; transport properties ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Experimental viscosity data of ethane, carbon dioxide, and three mole fractions of the binary system carbon dioxide + ethane in the temperature range 293.15〈T⩽633.15 K and in the density range 0.01⩽ρ⩽0.05 mol·L−1 reported earlier were evaluated simultaneously to find out a useful correlation and extrapolation scheme for the viscosity of binary systems in the range of moderate densities. A procedure based on the ideas of the modified Enskog theory has been found to give the best results. Dependent on temperature, the collision diameters related to the equilibrium radial distribution function at contact are fitted to viscosity values of the pure substances and of at least one mixture. The results are compared with experimental data from the literature. A recommendation is given concerning the density range in which the first density contribution to the viscosity coefficient of the system carbon dioxide + ethane is sufficient to be included.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    International journal of thermophysics 16 (1995), S. 1335-1351 
    ISSN: 1572-9567
    Schlagwort(e): n-alkanes ; propane ; second viscosity virial coefficient ; transport properties ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Results of five series of high-precision viscosity measurements on gaseous propane, each differing in density, are reported. The measurements were performed in a quartz oscillating-disk viscometer with small gaps from room temperature up to about 625 K and for densities between 0.01 and 0.05 mol · L−1. The experimental data were evaluated with a first-order expansion, in terms of density, for the viscosity. Reduced values of the second viscosity virial coefficients deduced from the zero-density and initial-density viscosity coefficients for propane and for furthern-alkanes are in close agreement with the theoretical representation of the Rainwater-Friend theory for the potential parameter ratios by Bich and Vogel. A new representation of the viscosity of propane in the limit of zero density is provided using the new experimental data and some data sets from literature. The universal correlation based on the extended principle of corresponding states extends over the temperature range 293 to 625 K with an uncertainty of ±0.5 % and deviates from earlier representations by about 1 % at the upper temperature limit.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    International journal of thermophysics 15 (1994), S. 1-31 
    ISSN: 1572-9567
    Schlagwort(e): ethane ; n-alkanes ; transport properties ; viscosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A new representation of the viscosity of ethane is presented. The representative equations are based upon a body of experimental data that have been critically assessed for internal consistency and for agreement with theory in the zero-density limit, vapor phase, and critical region. The representation extends over the temperature range from 100 K to the critical temperature in the liquid phase and from 200 K to the critical temperature in the vapor phase. In the supercritical region, the temperature range extends to 1000 K for pressures up to 2 MPa and to 500 K for pressures up to 60 MPa. The ascribed accuracy of the representation varies according to the thermodynamic state from ±0.5 % for the viscosity of the dilute gas near room temperature to ±3.0% for the viscosity at high pressures and temperatures. Tables of the viscosity, generated by the relevant equations, at selected temperatures and pressures and along the saturation line, are also provided.
    Materialart: Digitale Medien
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