Most of us have used fluorescence microscopy and are all too familiar with the advantages and disadvantages of this tool: easy identification of one or more labels that fluoresce at different wavelengths (color) against the relatively dark background of the biologic substrate, but we can't always get the spatial resolution that is needed to answer our questions. Electron microscopy, both transmission and scanning modes, offer much better spatial resolution, but present problems in localizing a label, particularly on the surface of a cell. Wouldn't it be great if an imaging technique were available that gave us the possibility of localizing one or more labels on the surface of a cell with resolution approaching electron microscopy. Karen Hedberg, Bruce Birrel, Douglas Habliston, and Hayes Griffith at the University of Oregon describe photoelectron imaging as the electron optical analogue of fluorescence microscopy, offering some of the advantages of both methods.

My Inter/Micro-84 presentation and subsequent article in The Microscope dealt with optimizing diffraction limited depth of field in photomacrography and is referenced by Brian Bracegirdle in his “Scientific Photomacrography. My analysis was based upon the classical solution for the diffraction pattern image of a point light source, using the Rayleigh criterion of resolution. H. Lou Gibson's method of treating combined diffraction and geometric blurring away from the object focal plane was used. The calculations and the experimental results indicated that a final print resolution, for the object focal plane, of 7 lines/mm (.29 mm Airy disk) gives an optimum balance of depth of field and resolution. The 7 lines/mm criterion is equivalent to an Abbe criterion of total magnification equal to 440 times the numerical aperture. The 500 times numerical aperture Abbe criterion recommended for microscopists with very acute vision corresponds to a maximum resolution of 6 lines/mm in the final image.

The Small Angle Cleavage Technique (SACT) developed by John McCaffrey is an extremely easy and cost-effective technique for producing superior cross sectional TEM samples from semiconductor and other single crystal materials. In the original technique, a special jig is required to be made in order to make too cuts in a 2 x 0.5 mm slotted capper TEM grid to create vertical tabs to mount the cleaved samples. This jig is not commercially available and the actual cutting and bending of the grids require a significant amount of manual dexterity. (Fat fingered fellows, like myself, need not apply.) Early on, John proposed a design for a commercial grid that could easily be bent into the required shape with no cutting, but the electron microscopy supply houses passed on the idea. Until now, microscopists wanting to experiment with the technique had to invest in the cost of having one of these jigs made.

After the trauma of birth, a baby is suddenly in a strange new world. The first order of the day is to make sense out of the jumbie of signals in order to form an image of what is out there. This image building proceeds with increased accuracy throughout adolescence. For those who labor in science the process never stops. They continue to try to refine their mental image of nature throughout their professional lives. In this effort, vision is the most valuable natural sense. In a happy blend of poetry and science, Diane Ackerman in her book, A Natural History of Senses, calls eyes “the great monopolist of our senses.” It is, in fact, hard to imagine experimental science without the power of vision. By the same token, any enhancement of visual acuity will promote the precision of our image of nature - the very essence of science.

Earlier versions of these essays have been posted primarily and repeatedly on the internet newsgroup <sci.research.careers> for approximately one year (March 1995 to March 1996). A number of versions are archived at a number of sites. These essays were written in the public interest and for the benefit of younger people who are in the grad. school to postdoc pipeline. This edition was cleaned up, reorganized somewhat, slightly shortened, and brought up to date.

People who are in the grad. school to postdoc pipeline are, for the most part, hoping to see their dreams come true with a real and decent career job in science. The purpose of this document is to inform these people about the realities that will be in conflict with their dreams.

A series of upgrades of an Electron Microprobe X-ray Analyzer (EPMA) were made to expand capabilities, increase efficiency, and cut costs. High technology EPUA features were acquired with cost effective expenditures. The driving force for our upgrade was to meet the continuing needs of corporate customers as well as many small companies which come to us for low-cost/high quality EPMA services.

Up to the present waypoint in this series on EM site magnetic fields, we have identified typical sources of time-varying magnetic field intensities, examined salient field characteristics and illustrated correct survey methods. Our goal this month is to analyze data collected at a proposed site and answer the key question of whether or not the candidate site is, as far as magnetic fields go, acceptable for EM use. In the process of analyzing the magnetic field survey data we will define some of the interpretive techniques involved and observe the distinction between localized (a.c. power) and non-localized (geomagnetic) time-varying fields. Finally, we will discuss the implications of EM susceptibility threshold vs. measured field ratios when considering remedial site shielding.