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  • 1
    Electronic Resource
    Electronic Resource
    Normal modes of a Si(100) double-paddle oscillator (2001)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 72 (2001), S. 1482-1491 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Six low-frequency eigenmodes of a double-paddle oscillator have been measured and have been identified with a finite-element model. The internal friction Q−1 of these modes has been measured in the range of 4–80 K. Only one of the oscillator's modes has a Q−1〈3×10−8 below 40 K, which is furthermore very reproducible. All other modes have a higher internal friction which is not as reproducible and also sometimes changes after thermal cycling. It is shown that the internal friction of the different modes is related to the restoring force needed to hold the oscillator in place. The finite-element model is used to predict the damping of the different modes. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1340559
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of Age on QT Variability (2000)
    Springer
    Pediatric cardiology 21 (2000), S. 411-415 
    Details
    ISSN: 1432-1971
    Keywords: Key words: QT variability — Heart rate variability — Vagal — Sympathetic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. Heart rate variability is influenced significantly by age. Recent studies have shown the utility of QT variability to study temporal repolarization lability, and increased QT variability is reportedly associated with sudden death. Because beat-to-beat QT interval variability appears to closely follow heart rate variability, this study investigated the relationship between age and QT variability. We obtained QT variability measures in 34 adults (22–55 years of age) and 15 children (6–14 years of age) using a novel algorithm to compute beat-to-beat QT intervals. QT variability corrected for mean QT interval was significantly inversely correlated with age. Coherence in the band of 0 to 0.5 Hz and high-frequency coherence (0.15–0.5 Hz) were also significantly inversely correlated with age. QTvi (QT variability corrected for mean QT interval over heart rate variability corrected for mean heart rate) was not significantly related to age in supine posture during spontaneous or controlled breathing, whereas there was a modest negative relationship in standing posture. These findings suggest that coherence between QT and heart rate time series appears to be modulated by cardiac vagal activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002460010099
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  • 3
    Electronic Resource
    Electronic Resource
    Experiment to measure the Lamb shift in muonic hydrogen (2000)
    Springer
    Hyperfine interactions 127 (2000), S. 161-166 
    Details
    ISSN: 1572-9540
    Keywords: proton ; proton radius ; muon ; muonic hydrogen ; Lamb shift
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The contribution of the root mean square (RMS) proton charge radius to the Lamb shift (2S–2P energy difference) in muonic hydrogen (μp) amounts to 2%. Apart from the uncertainty on this charge radius, theory predicts the Lamb shift with a precision on the ppm level. We are going to measure ΔE (2 S1/2(F=1)–2 P3/2(F=2)) in a laser resonance experiment to a precision of 30 ppm (i.e., 10% of the natural linewidth) and to deduce the RMS proton charge radius with 10−3 relative accuracy, 20 times more precise than presently known. The most important requirement for the feasibility of such an experiment, namely the availability of a sufficient amount of long lived metastable μp atoms in the 2S state, has been investigated in a recent experiment at PSI. Our analysis shows that in the order of one percent of all muons stopped in low pressure hydrogen gas form a long lived μp(2S) with a lifetime of the order of 1 μs. The technical realization of our experiment involves a new high intensity low energy muon beam, an efficient low energy muon entrance detector, a randomly triggered 3 stage laser system providing the 0.5 mJ, 7 ns laser pulses at 6.02 μm wavelength, and a combination of a xenon gas proportional scintillation chamber (GPSC) and a microstrip gas chamber (MSGC) with a CsI coated surface to detect the 2 keV X rays from theμp(2P → 1S) transition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1012679114531
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  • 4
    Electronic Resource
    Electronic Resource
    Collisional quenching of metastable states of antiprotonic helium by hydrogen and deuterium molecules (2001)
    Springer
    The European physical journal 13 (2001), S. 305-316 
    Details
    ISSN: 1434-6079
    Keywords: PACS. 36.10.-k Exotic atoms and molecules (containing mesons, muons, and other unusual particles) – 42.62.Fi Laser spectroscopy – 34.20.Gj Intermolecular and atom-molecule potentials and forces
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The quenching of metastable states of antiprotonic helium by collisions with hydrogen and deuterium molecules was studied. A systematic investigation of the delayed annihilation time spectra at various H2 and D2 admixture ratios at the ppm level revealed characteristic changes of their shape, which indicated a strong principal and orbital quantum number dependent quenching of levels in both cases. Applying a laser spectroscopy technique to measure the lifetimes of individual states and cascades we deduced H2 and D2 quenching cross-sections for the states (n, l )= (39, 35) and (37, 34). These cross-sections establish for D2 molecules the strong increase of the quenching efficiency with increasing principal quantum number n of the state under investigation previously reported for the case of H2 admixtures. Our experiments indicate that the low-n state (37, 34) is somewhat less affected by D2 than by H2, while the high-n state (39, 35) is equally quenched by both isotopes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100530170246
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