996 research outputs found
Electronic compressibility and charge imbalance relaxation in cuprate superconductors
In the material SmLaSrCuO with alternating intrinsic
Josephson junctions we explain theoretically the relative amplitude of the two
plasma peaks in transmission by taking into account the spatial dispersion of
the Josephson Plasma Resonance in direction due to charge coupling. From
this and the magnetic field dependence of the plasma peaks in the vortex solid
and liquid states it is shown that the electronic compressibility of the
CuO layers is consistent with a free electron value. Also the London
penetration depth near can be
determined. The voltage response in the -curve of a
BiSrCaCuO mesa due to microwave irradiation or current
injection in a second mesa is related to the nonequilibrium charge imbalance of
quasiparticles and Cooper pairs and from our experimental data the relaxation
time is obtained.Comment: 2 pages, 2 figures, phc-proc4-auth.cls, to be published in Physica C
as a proceeding of M2S-HTSC Rio 200
Identifying intrinsic and reflexive contributions to low-back stabilization
Motor control deficits have been suggested as potential cause and/or effect of a-specific chronic low-back pain and its recurrent behavior. Therefore, the goal of this study is to identify motor control in low-back stabilization by simultaneously quantifying the intrinsic and reflexive contributions. Upper body sway was evoked using continuous force perturbations at the trunk, while subjects performed a resist or relax task. Frequency response functions (FRFs) and coherences of the admittance (kinematics) and reflexes (sEMG) were obtained. In comparison with the relax task, the resist task resulted in a 61% decrease in admittance and a 73% increase in reflex gain below 1.1 Hz. Intrinsic and reflexive contributions were captured by a physiologically-based, neuromuscular model, including proprioceptive feedback from muscle spindles (position and velocity) and Golgi tendon organs (force). This model described on average 90% of the variance in kinematics and 39% of the variance in sEMG, while resulting parameter values were consistent over subjects
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