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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 7 (1987), S. 95-106 
    ISSN: 1434-6079
    Keywords: 31.30 ; 31.90
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The idea of the parametrization of atomic interactions, such as the hyperfine interaction, the spin-orbit interaction and the isotopic field shift, is reviewed from the point of view of atomic many-body theory. The close analogy between Goldstone perturbation diagrams and the angular-momentum diagrams of Jucys et al. is used extensively in the analysis. In the non-relativistic limit, when only electrostatic perturbations are considered, it is verified that the hyperfine interaction can be exactly described by the effective one-body operator, introduced by Harvey, providedLS-dependent parameters are used. When relativity is considered, it is shown that the consideration of effective one-body effects leads to the theory of Sandars and Beck, withLS-independent parameters, while the remaining effects can be represented byLS-dependent one-body operators of higher tensor ranks. When the same idea is applied to the spin-orbit interaction and to the isotope shift, it is shown that these two interactions can be represented by the same effective operators. This implies that theJ dependence of the field shift should show certain similarity with the fine structure, as observed experimentally and, in particular, that this shift should follow the Landé interval rule close toLS coupling. The approach developed here of introducing tensor operators of higher tensor ranks to represent the relativistic effects is compared with the more conventional approach of using standard operators and intermediate-coupling wave functions.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Medical & biological engineering & computing 24 (1986), S. 83-90 
    ISSN: 1741-0444
    Keywords: Computer analysis ; Dead space calculation ; Distribution of ventilation ; Gas mixing ; Linear estimation of exponentials ; Multiple breath nitrogen washout ; Nitrogen elimination pattern ; Ventilatory efficiency ; z-transform
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract A method of analysing multiple-breath nitrogen washouts is described and discussed. The method is objective and introduces no weighting into the results. The necessary raw data are obtained from a computer-assisted nitrogen washout test. During the analysis, objective parameters which characterise the alveolar ventilation in terms of nitrogen elimination pattern and gas-mixing efficiency are calculated, together with estimates of functional residual capacity (FRC), tidal volume, dead space, and effective part of the tidal volume. The elimination pattern is described through linear fitting of exponential models to the obtained washout course and is performed by using the z-transform. The dead space and the effective part of the tidal volume are estimated from a gas-mixing model. The applied estimation procedure difines a dead space which is larger than the corresponding single-breath dead space and has been designated ‘effective dead space’. The gas-mixing efficiency is described by two indices, one describing the efficiency within an idealised breath and the other the overall efficiency of the lungs. The calculation algorithms are fast and the results are easy to interpret, which makes the method suitable for clinical online applications. The method has been evaluated in a group of 24 healthy newborns at about 26 hours of age, but the application is not restricted to this category of patient.
    Type of Medium: Electronic Resource
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