7,661 research outputs found

    Quantum Impurities and the Neutron Resonance Peak in YBa2Cu3O7{\bf YBa_2 Cu_3 O_7}: Ni versus Zn

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    The influence of magnetic (S=1) and nonmagnetic (S=0) impurities on the spin dynamics of an optimally doped high temperature superconductor is compared in two samples with almost identical superconducting transition temperatures: YBa2_2(Cu0.97_{0.97}Ni0.03_{0.03})3_3O7_7 (Tc_c=80 K) and YBa2_2(Cu0.99_{0.99}Zn0.01_{0.01})3_3O7_7 (Tc_c=78 K). In the Ni-substituted system, the magnetic resonance peak (which is observed at Er_r \simeq40 meV in the pure system) shifts to lower energy with a preserved Er_r/Tc_c ratio while the shift is much smaller upon Zn substitution. By contrast Zn, but not Ni, restores significant spin fluctuations around 40 meV in the normal state. These observations are discussed in the light of models proposed for the magnetic resonance peak.Comment: 3 figures, submitted to PR

    Magnetic resonance peak and nonmagnetic impurities

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    Nonmagnetic Zn impurities are known to strongly suppress superconductivity. We review their effects on the spin excitation spectrum in YBa2Cu3O7\rm YBa_2Cu_3O_{7}, as investigated by inelastic neutron scattering measurements.Comment: Proceedings of Mato Advanced Research Workshop BLED 2000. To appear in Nato Science Series: B Physic

    ANTICIPATION EFFECT ON KNEE JOINT STABILITY DURING PLANNED AND UN-PLANNED MOVEMENT TESTS IN LABORATORY

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    The purpose of this study was to investigate the anticipation effect on knee stability during functional test in laboratory. Ten healthy male subjects were recruited and instructed to perform a series of planned and un-planned stop-jumping tasks. Knee joint kinematics was measured by a motion analysis system. The subjects demonstrated different abduction and rotation angles for reactive tasks. This suggested that if knee abduction or rotational stability is considered as a primary measurement in documenting knee stability, such as in the investigation of rehabilitation progress after anterior cruciate ligament reconstruction, both planned and un-planned tasks should be considered as to take the anticipation effect into account

    High energy spin excitations in YBa_2 Cu_3 O_{6.5}

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    Inelastic neutron scattering has been used to obtain a comprehensive description of the absolute dynamical spin susceptibility χ(q,ω)\chi'' (q,\omega) of the underdoped superconducting cuprate YBa_2 Cu_3 O_{6.5} (Tc=52KT_c = 52 K) over a wide range of energies and temperatures (2meVω120meV2 meV \leq \hbar \omega \leq 120 meV and 5KT200K5K \leq T \leq 200K). Spin excitations of two different symmetries (even and odd under exchange of two adjacent CuO_2 layers) are observed which, surprisingly, are characterized by different temperature dependences. The excitations show dispersive behavior at high energies.Comment: 15 pages, 5 figure

    MYCL genotypes and loss of heterozygosity in non-small-cell lung cancer.

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    Some studies have suggested that the S allele of the MYCL oncogene, which results from an intragenic EcoRI restriction fragment length polymorphism (RFLP), may be associated with cancer susceptibility. In addition, this allele has also been linked to metastases and adverse survival in certain cancers, although studies of lung cancer patients from different populations have yielded controversial results. We studied 108 cases of surgical resected non-small-cell lung cancer (NSCLC) and found no evidence that MYCL genotypes were associated with tumour progression or a worse prognosis. However, the presence of loss of heterozygosity (LOH) at this chromosome 1p32 locus correlated significantly with regional lymph node involvement, as well as advanced TNM stage. These data indicate the existence of a chromosome 1p candidate tumour-suppressor gene(s), possibly in linkage disequilibrium with the EcoRI RFLP in specific populations, which appears to play a role in determining tumour progression in NSCLC. Refined mapping of the critical region of loss should help attempts to identify and clone the candidate gene

    EXCESSIVE TIBIAL ROTATION IS RESTORED AFTER ANATOMICAL DOUBLE BUNDLE ANTERIOR CRUCIATE LIGAMENT RECONSTRUCTION

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    Recent studies suggested that tibial rotaion was not restored after single bundle anterior cruciate ligament (ACL) reconstruction. This study aimed to determine if excessive tibial rotation would be restored by anatomical double bundle ACL reconstruction. Ten male subjects with unilateral ACL injury were prospectively assessed with a high demanding task before and after ACL reconstruction. Knee kinematics during pivoting movement was measured by a motion analysis system. The tibial rotation was reduced in the reconstructed knee after ACL reconstruction than the deficient knee (
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