Biomedical subjects

Marvin A Schofield

Publications and source records attributed to Marvin A Schofield.

2 recordsLinked to original sources

PubMed2004

Direct evidence for negative grain boundary potential in Ca-doped and undoped YBa2Cu3O7-x.

Using electron holography in a transmission electron microscope, we obtained direct evidence for the reduction of negative charge at grain boundary dislocations in Ca-doped YBa2Cu3O7 (YBCO) when compared to undoped YBCO. Because of the finite width of the valence band in the superconducting CuO2 planes, the negative grain boundary charge can lead to a depletion of electron holes available for superconductivity. A significant reduction in the size of the perturbed region in the Ca-doped samples appears to be the principal mechanism for the improved interfacial superconductivity.

Journal Article↗

PubMed2003

Fast phase unwrapping algorithm for interferometric applications.

A wide range of interferometric techniques recover phase information that is mathematically wrapped on the interval (-pi, pi). Obtaining the true unwrapped phase is a longstanding problem. We present an algorithm that solves the phase unwrapping problem, using a combination of Fourier techniques. The execution time for our algorithm is equivalent to the computation time required for performing eight fast Fourier transforms and is stable against noise and residues present in the wrapped phase. We have extended the algorithm to handle data of arbitrary size. We expect the state of the art of existing interferometric applications, including the possibility for real-time phase recovery, to benefit from our algorithm.

Journal Article↗