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  • 1
    Electronic Resource
    Electronic Resource
    Relationship between age and heart rate variability in supine and standing postures: A study of spectral analysis of heart rate (1994)
    Springer
    Pediatric cardiology 15 (1994), S. 14-20 
    Details
    ISSN: 1432-1971
    Keywords: Age ; Heart rate variability ; Spectral analysis ; Cholinergic ; Adrenergic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We compared heart rate variability measures of 11 normal children (4–12 years) to 23 normal adults (21–43 years) to study the effect of age on heart rate variability measures. Children had a significantly higher supine and standing heart rate and lower supine and standing systolic diastolic blood pressure. Children also had a significantly higher supine standard deviation of HR, supine low frequency (0.01–0.05 Hz) (p〈0.005), supine high frequency (0.2–0.5 Hz) (p〈0.001), and standing high frequency powers (p〈0.005) compared to adults. The ratio of mid frequency (0.07–0.15 Hz) to high frequency power (0.2–0.5 Hz) upon standing was significantly lower in children (p〈0.005). While there was a significant increase of the mid frequency power from supine to standing posture in the adult group (p〈0.02), there was no such significant increase in children. There were also significant negative correlations between age and supine low frequency, mid frequency, and high frequency powers, and standing high frequency power. These findings illustrate a decrease of cholinergic and an increase of adrenergic modulation of heart rate variability with age (4–43 years).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00797000
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  • 2
    Electronic Resource
    Electronic Resource
    Glasslike elastic properties in the ω-β alloys (1994)
    Springer
    The European physical journal 93 (1994), S. 479-490 
    Details
    ISSN: 1434-6036
    Keywords: 63.50. + ; 61.42. + h ; 62.40. + i
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have measured the internal friction and speed of sound in several polycrystalline alloys, using compound torsional oscillators at frequencies between 60 kHz and 100 kHz and temperatures between 50 mK and 100 K. By combining these data with existing elastic and thermal data on similar alloys, we find that those alloys which can undergo diffusionsless phase transitions, such as Ti:Nb, Ti:V, or Zr:Nb in certain ranges of composition have glasslike excitations, since they have elastic properties which agree in magnitude and temperature dependence with those of amorphous solids. By contrast. crystalline continuous solution alloys, such as Nb:Ta, or alloys with diffusive phase transitions, such as high-pressure quenched Al94Si6, have the same elastic properties as are known for crystals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01314252
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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