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  • 1
    ISSN: 1434-6079
    Keywords: PACS. 36.40.-c Atomic and molecular clusters – 82.33.Hk Reactions on clusters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Spectroscopic experiments have been performed, providing emission and excitation spectra of calcium atoms trapped on argon clusters of average size 2 000. The two experimental spectra fall in the vicinity of the calcium resonance line 1P 1 → 1S0 at 422.9 nm. The excitation spectrum consists in two bands located on each side of the resonance line of the free calcium. In addition, Monte Carlo calculations, coupled to Diatomics-In-Molecule potentials are employed to simulate the absorption spectrum of a single calcium atom in the environment of a large argon cluster of average size 300. The theoretical absorption spectrum confirms the existence of two bands, and shows that these bands are characteristic of a calcium atom located at the surface of the argon cluster and correspond to the excited 4p orbital of calcium either perpendicular or parallel to the cluster surface. The precise comparison between the shape of the absorption spectrum and that of the fluorescence excitation spectrum shows different intensity ratios. This could suggest the existence of a non adiabatic energy transfer that quenches partly the fluorescence of trapped calcium. Another explanation, although less likely, could be a substantial dependence of the calcium oscillator strength according to the alignment of the calcium excited orbital with respect to the cluster surface. The emission spectrum always shows a band in the red of the resonance line which is assigned to the emission of calcium remaining trapped on the cluster. When exciting the blue band of the excitation spectrum, the emission spectrum shows a second, weak, component that is assigned to calcium atoms ejected from the argon clusters, indicating a competition between ejection and solvation.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    European journal of applied physiology 70 (1995), S. 541-544 
    ISSN: 1439-6327
    Keywords: Exercise ; Children ; Physiological evaluation ; Lactate threshold
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The purpose of this study was to determine the anaerobic threshold of children by the analysis of saliva collected during field tests. A group of 25 children (mean age, 10.5 years) performed an incremental exercise test on a track, consisting of 4-min stages at increasing running velocities. Before each test (at rest) and at the end of each stage, both blood (via finger pricks) and saliva samples (for measurement of salivary concentrations of Na+ and Cl−) were collected to determine lactate threshold (Th1a-) and saliva threshold (Thsa), respectively. There were no significant differences between values of Th1a- and Thsa when expressed either as running velocity [mean Th1a-, 10.73 (SD 1.96) km · h−1; mean Thsa, 10.89 (SD 1.69) km · h−1] or heart rate [Th1a-, 182(SD 14) beats · min−1 Thsa 183 (SD 11) beats · min−1]. In addition, correlations between Thsa and Th1a were high, when both values were expressed as running velocity in kilometres per hour (r = 0.89;P 〈 0.001), or heart rate in beats per minute (r = 0.90;P 〈 0.001). In conclusion, these findings suggested that saliva analysis would be a valid method for anaerobic threshold determination in field tests.
    Type of Medium: Electronic Resource
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