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We report the nonlinear response of tissue and nerve fibers in the earthworm Lumbricus terrestris to sinusoidal electric field excitations. A High-Tc Superconducting Quantum Interference Device (SQUID) magnetometer detects the magnetic field generated by complex currents in the animal. SQUID signals are processed on a Fast Fourier Transform (FFT) spectrum analyser. Use of the SQUID eliminates low frequency polarization impedance and field distortion that would be present near pickup electrodes. Electrical 4-probe harmonic response measurements of the excised nerve fiber are then compared to the driven Hodgkin-Huxley active transport model. [ABSTRACT FROM AUTHOR]

Numerical modeling studies have been carried out for the design of superconducting and high-permeability shields for SQUID-based nondestructive evaluation and biomagnetic measurements. We used finite-element-method software to model magnetic shields with both axial and planar symmetry in axial and transverse uniform noise fields. Improvements in signal-to-noise ratio at the location of the SQUID were calculated for different shield geometries with line current and magnetic dipole sources at various locations near the shield. [ABSTRACT FROM AUTHOR]

Describes a high temperature superconducting quantum interference device-based eddy current probe that incorporates a hybrid sheet-inducer coil design for nondestructive evaluation of conducting materials. Device operation in magnetically noisy environments; Flaw response; Comparison with a conventional sheet inducer.

Examines the results of investigation on ambient noise reduction using localized high-temperature superconducting (HTS) passive magnetic shields. How the results were quantified; Discussion of relative merits of noise reduction techniques.