X-Message-Number: 4764 Date: Fri, 11 Aug 1995 09:55:27 -0700 (PDT) From: Joseph Strout <> Subject: Re: electron holography Electron holography can be accomplished in a variety of ways, and this has been done with some success. However, it's not that much different from conventional transmission electron microscopy; you have the same problems of sample thickness and cooking. Theoretical treatments of electron holography generally assume a sample thickness of about 5 nm or less. More elaborate theory can work with thicker samples, but you run into a real practical limitation due to electron scattering: as the thickness increases, electrons start colliding and end up going every which way, producing useless noise. As the thickness increases, the signal-to-noise ratio drops. When it works, e. holography has improved the resolution by a factor of about 1.5 as compared to convential imaging. Most of the really exciting applications of this technique have been in imaging magnetic fields on a very fine scale (e.g., even individual "flux quanta" in a superconductor). So, while it's a neat technology and useful for a lot of things, to use it for a brain recording would still requiring slicing your brain very thin and then cooking it. Much of the above info, plus a good mathematical treatment, can be found in a review article: Cowley, J.M., "Twenty forms of electron holography" Ultramicroscopy 41: 335-348 (1992). ,------------------------------------------------------------------. | Joseph J. Strout Department of Neuroscience, UCSD | | http://sdcc3.ucsd.edu/~jstrout/ | `------------------------------------------------------------------' Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=4764