High resolution in-vivo electrode localization using microfocal X-rays.

Thesis (M. Eng. and S.B.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2006.Statement of responsibility "by Daniel Oreper" taken from abstract, p. 1. Leaf 109 blank.Includes bibliographical references (leaf 108).Neuroscientists lack the ability to perform in-vivo electrode localization with high accuracy, especially in deep brain structures. The design, implementation and testing of a microfocal x-ray stereo system that offers an efficient, accurate, and relatively low-cost solution this localization problem is presented. The results indicate the ability to localize a targets to within -50 microns, in a brain-tissue-based frame. This accuracy is approximately twice as good as than the existing gold standard in electrophysiology (microlesions), and, unlike the microlesion method, the stereo microfocal x-ray method has important advantages. In particular, while only tens of neuronal recording sites can be reliably reconstructed with the microlesion method, microfocal x-ray method can be repeatedly performed to accurately estimate an essentially unlimited number of serial penetrations, and the localization results are available in nearly real time without animal sacrifice.M.Eng.and S.B

Convection in Arc Weld Pools Electromagnetic and surface tension forces are shown to dominate flow behavior, in some cases producing double circulation loops in the weld pool

ABSTRACT. A mathematical model has been developed to account for convection and temperature distributions in stationary arc weld pools driven by buoyancy, electromagnetic and surface tension forces. It is shown that the electromagnetic and surface tension forces dominate the flow behavior. In some cases, these forces produce double circulation loops, which are indirectly confirmed by experimental measurements of segregation in the weld pool. It is also shown that the surface tension driven flows are very effective in dissipating the incident energy flux on the pool surface which, in turn, reduces the vaporization from the weld pool