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  • 11
    Digitale Medien
    Digitale Medien
    Transport and μSR studies at p ∼1/8 in the Bi-2212 and Y-123 phases (1999)
    Springer
    Journal of low temperature physics 117 (1999), S. 1163-1167 
    Details
    ISSN: 1573-7357
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The so-called 1/8 effect, namely, the anomalous suppression of superconductivity at the hole concentration per Cu in the CuO 2 plane, p, ∼ 1/8 has been investigated in the partially Zn-substituted Bi-2212 and Y-123 phases by measuring the Hall effect and the muon spin relaxation ( μSR ). The Hall angle has been found to exhibit large enhancement at p ∼ 1/8 in Bi 2 Sr 2 Ca 1−x Y x (Cu 1−y Zn y ) 2 O 8+δ with y=0.025. In YBa 2 Cu 3−2y Zn 2y O 7−δ with y=0.025, anomalous enhancement of the muon spin depolarization has been observed at p ∼ 1/8, indicating that the magnetic correlation between Cu spins is enhanced at p ∼ 1/8. These results support the stripe model and the proposition that the 1/8 effect is common to all high-T c cuprates with the CuO 2 plane.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1022559331206
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  • 12
    Digitale Medien
    Digitale Medien
    Spin Gap and Hole Pairing of Sr14−x A x Cu24O41(A = Ca and La) Single Crystals Studied by the Electrical Resistivity and Thermal Conductivity (1999)
    Springer
    Journal of low temperature physics 117 (1999), S. 1689-1693 
    Details
    ISSN: 1573-7357
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We have measured the electrical resistivity ρ and the thermal conductivity κ of Sr 14−x A x Cu 24 O 41(A = Ca and La) single crystals. The Arrhenius plot of ln ρ vs T −1 gives two kinds of activation energy with a boundary temperature T ρ . The activation energy at T 〈 T ρ is in approximate agreement with the spin gap in the ladder estimated from the NMR measurements, suggesting that holes in the ladder are paired and localized at T 〈 Tρ. The observed κ has been analyzed to be composed of κ ph , κ spin and κ hole due to phonons, spins and holes, respectively. The κ ph exhibits a small peak at ∼ 30 K in every direction of every single-crystal. The contribution of κ spin is observed along the c-axis except for x(Ca) ≥ 6, and the spin gap, which corresponds to the spin excitation from spin-singlet to spin-triplet, has been estimated to be ∼ 420 K. For x(Ca) ≥ 6, the spin gap, which corresponds to the destruction of spin-singlet pairs i. e. the dissociation of hole pairs, has been estimated from κ along the c-axis at T 〉 T ρ to decrease with increasing x(Ca).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1022588421579
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  • 13
    Digitale Medien
    Digitale Medien
    Accurate Three-Nucleon Bound-State Calculation with an Extended Separable Expansion of the Two-Body T-Matrix (1998)
    Springer
    Few body systems 23 (1998), S. 53-73 
    Details
    ISSN: 1432-5411
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract. An accurate solution for the three-nucleon bound state is obtained within 1 keV in the binding energy and, on the whole, better than 1% in the wave function, using a new systematic and efficient method. The method is based on a recently developed separable expansion for any finite-range interaction, in which a rigorous separable series for the two-body t-matrix is obtained by expanding the wave function in terms of a complete set of basis functions inside the range of the potential. In order to treat a potential with a strong repulsive core, as in the case of the Argonne potential, we develop a two-potential formalism. The expansion starts with a few EST (Ernst, Shakin, and Thaler) terms in order to accelerate the convergence and continues with an orthogonal set of polynomials, avoiding the known difficulties of a pure EST expansion. Thus, several techniques are combined in the present extended separable expansion (ESE). In this way, the method opens a new systematic treatment for accurate few-body calculations resulting in a dramatic reduction in the CPU time required to solve few-body equations.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s006010050064
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  • 14
    Digitale Medien
    Digitale Medien
    Relationship between respiratory failure and plasma noradrenaline levels in amyotrophic lateral sclerosis (1997)
    Springer
    Clinical autonomic research 7 (1997), S. 173-177 
    Details
    ISSN: 1619-1560
    Schlagwort(e): amyotrophic lateral sclerosis ; plasma noradrenaline ; head-up tilt test ; sympathetic hyperactivity ; respiratory failure ; chemoreceptor
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract We evaluated plasma noradrenaline (NA) levels at rest and during head-up tilt test in 20 patients with sporadic amyotrophic lateral sclerosis (ALS). Their fasting plasma NA levels ranged from 195 to 4227 pg/ml. The average plasma NA level was 483 pg/ml in five ambulatory patients, 341 in two wheelchair-bound patients, 1264 in 11 bedridden patients, and 208 in two respirator-dependent patients whose disability grading was the worst among the four groups. Arterial carbon dioxide (PCO2) was evaluated as a measure of respiratory function. The coefficient of correlation between PCO2 and plasma NA wasr=0.654 (p〈0.01). Either respiratory failure or lower motor neuron dysfunction may relate to the elevation of plasma NA levels. In the two bedridden patients, plasma NA levels and heart rate at rest increased significantly as the disease progressed. Cardiovascular responses to head-up tilting were normal. These data suggest that the elevation of plasma NA levels may be related to progression of respiratory failure and lower motor neuron dysfunction. In conclusion, sympathetic hyperactivity in ALS is considered to be not primary, but secondary to somatic motor disabilities and respiratory failure.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02267978
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  • 15
    Digitale Medien
    Digitale Medien
    Crystal Growth by the TSFZ Method and Superconducting Properties of the Tetragonal 1-2-3 Type Cuprates (1999)
    Springer
    Journal of low temperature physics 117 (1999), S. 705-709 
    Details
    ISSN: 1573-7357
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Single crystals of Ca 0.5 La 1.25 Ba 1.25 Cu 3O y and NdBaSrCu 3 O y with the dimensions of the order of 1×1×0.5 mm 3 have been grown by the travelling-solvent floating zone method. As-grown single-crystals are tetragonal and non-superconducting. Through the annealing in oxygen, single crystals of Ca 0.5 La 1.25 Ba 1.25 Cu 3 O y have become superconductors with T c = 55 - 65 K, keeping the tetragonal structure. On the other hand, single crystals of NdBaSrCu 3 O y have changed from tetragonal to orthorhombic through the annealing in oxygen, though they have become superconductors with T c = 55 K.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1022537026351
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