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  • Human infants  (1)
  • ac bridge calibration  (1)
  • Springer  (2)
  • National Academy of Sciences
  • 1
    Electronic Resource
    Electronic Resource
    Laser Doppler velocimetry in retinal arteries of infants (1995)
    Springer
    Lasers in medical science 10 (1995), S. 267-272 
    Details
    ISSN: 1435-604X
    Keywords: Blood flow pulsatility ; Human infants ; Laser Doppler velocimetry ; Retinal blood flow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract The present study was conducted to assess the feasibility of laser Doppler velocimetry in young infants, as a prelude to ultimately undertaking such measurements in premature infants. A portable, unidirectional laser Doppler velocimeter was developed based on a Kowa RC-2 hand-held fundus camera. Six infants between 1 and 21 weeks of age were studied. Relative red blood cell velocity (δfmax) at the centre of retinal arteries was measured over approximately 10 heart cycles. A pulsatility parameter (P=1−δfmax.dia/δfmax.sys), a summary index of vascular status, was determined from the average diastolic and systolic values of δfmax. Velocity waveforms were obtained in four of the six infants. Arterial pulsatility for the group was 0.63±0.13. Precise non-invasive measurement of arterial red blood cell velocity waveforms in young infants was achieved. The high signal-to-noise ratio and temporal resolution of this data suggest that relative measurements of retinal blood flow may permit assessment of haemodynamic changes in premature infants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02133619
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  • 2
    Electronic Resource
    Electronic Resource
    Electric dipole moments in polar solvents. I. Audiofrequency measurement with slightly conducting solutions (1973)
    Springer
    Journal of solution chemistry 2 (1973), S. 373-392 
    Details
    ISSN: 1572-8927
    Keywords: Electric dipole moment ; ac bridge calibration ; dielectric cell ; electrical model ; dielectric constant of ionic solutions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Audiofrequency methods were used to measure dielectric constants of dilute solutions containing electrolytes up to free-ion concentrations of 10−4 M. Using a calibrated transformer bridge, capacitance was measured with an accuracy of 0.03 pF at a conductance of 100 μmho and within 0.3 pF at 800 μmho. Evaluation of the double-layer capacitance from the frequency dependence of the data is discribed. The effect of the free ions on the dielectric constant is found to be relatively large and in reasonable agreement with the prediction of the Debye-Falkenhagen theory. The calculation of the electric dipole moment for polar solutes, including ion pairs, is discussed in terms of Kirkwood's theory. Experimental tests are described for finding out whether possible deviations of Kirk-wood's correlation factors from unity may be neglected. These tests involve changing the solvent and the temperature. The tests were satisfied for the ion pairs of tetraisoamylammonium nitrate and for nitrobenzene in chlorobenzene and acetic acid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00713251
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    Paper (German National Licenses)
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