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  • 1
    Electronic Resource
    Electronic Resource
    Propranolol unmasks class III like electrophysiological properties of norepinephrine (1993)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 348 (1993), S. 643-649 
    Details
    ISSN: 1432-1912
    Keywords: Epicardial mapping ; Class-III-antiarrhythmic drugs ; Adrenoceptors ; Propranolol ; β-blockers ; Norepinephrine ; Dispersion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Isolated perfused spontaneously beating rabbit hearts were treated with increasing concentrations of norepinephrine (0.01, 0.1, 0.5 μmol/l) either alone or in presence of propranolol (0.1 μmol/l). For analysis of the epicardial activation and repolarization process and epicardial mapping (256 unipolar leads) was performed. For each electrode the activation and repolarization time was determined. From these data the “breakthrough-points” (BTP) of epicardial activation were determined. At each electrode an activation vector (VEC) was calculated giving direction and velocity of the local excitation wave. The beat similarity of various heart beats (under NE) compared to control was evaluated by determination of the percentage of identical BTP and of similar VEC (deviation ≤5°). Moreover at each electrode the local activation recovery interval (ARI) and its standard deviation (of 256 leads, dispersion, DISP) were determined. Norepinephrine alone (0.01, 0.1, 0.5 μmol/l) led to an increase in left ventricular pressure, heart rate and DISP with concomittant frequency dependent reduction in ARI, and to changes in the epicardial activation pattern (reduction in BTP, VEC). We found that in the presence of propranolol (0.1 μmol/l) norepinephrine prolonged ARI and reduced ARI-dispersion. This effect was not due to changes in heart rate. The disturbing effects on the activation pattern were dimished. These effects could be prevented by pretreatment with 1 μmol/l prazosine. From these results we conclude, that norepinephrine prolongs the relative action potential duration via stimulation of α1-adrenoceptor and enhances cellular coupling. Thus, the antiarrhythmic properties of propranolol may at least in part be due to an unmasking of class III like norepinephrine effects and additional reduction in dispersion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00167242
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Unusual Photon Energy Dependence of the Cooper Pair Breaking Rate in YBa2Cu3O7−δ Epitaxial Thin Films (1999)
    Springer
    Journal of superconductivity 12 (1999), S. 675-680 
    Details
    ISSN: 1572-9605
    Keywords: YBCO ; Cooper pair ; thin films ; ultrafast phenomena
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The transient photoimpedance response of epitaxial YBa2Cu3O7−δ thin films has been studied using 100 fs Ti:Sapphire laser pulse excitation. Both temperature and photon energy dependence of the fast optical response signal (whose temperature dependence can be explained by a kinetic inductance model involving Cooper pair breaking) were studied. The pair breaking rate is strongly photon energy-dependent, with a resonance around 1.5 eV with a width of only 100 meV, which is very surprising given the strong electron correlation in this metallic system and may be explained in terms of the stripe phase model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007708304186
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Microstructures of high-J c melt-textured YBa2Cu3O7−x /Ag superconductors (1994)
    Springer
    Journal of superconductivity 7 (1994), S. 947-950 
    Details
    ISSN: 1572-9605
    Keywords: Critical current density ; Ag addition ; grain alignment ; flux pinning ; defect structure ; YBCO ; melt-texturing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Silver has been previously added to the melt-textured YBa2Cu3O7−x in order to increase the critical current density (J c ) of these materials. However, the effect of this addition on theJ c is presently unclear. The purpose of this study is to investigate the effect of silver on both critical current density and the microstructure of the melt-textured YBa2Cu3O7−x superconductors by means of X-ray diffraction, optical polarized microscopy, and transmission electron microscopy (TEM). TheJ c of the MTG YBCO/Ag samples is more than 104A/cm2 under the 5 kOe magnetic field. It has been shown that as the concentration of silver increases, the fraction of the 211 phase dispersed within the 123 matrix decreases. Therefore, theJ c slightly decreases. These results, together with the effect of the 211 phase, dislocations, and other structure defects on flux pinning, are described in this paper.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00732277
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    Paper (German National Licenses)
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