We're all interested in food. Food is the sustenance of life. And you're interested in microscopy, or else you would not be reading this column. So here's a web site that will appeal to both of your interests. Miloš Kaláb is the author of the web site, and he's enlisted a host of food scientists to assist him. There's no lack of expertise here!

The home page can send you to many locations, but let's begin with the site that deals with microscopy. It is said that the earliest microscopists trained their simple instruments on food, mainly to look for contaminants. We are then treated to a primer on microscopy, beginning with light microscopy, then advancing to electron microscopy.

Sometimes a scientist or laboratory manager has the opportunity to be involved in the design of a new building for housing sensitive instruments, such as electron microscopes. Unfortunately, few of us are trained in the necessary skills, and “learning the hard way”, by making mistakes, is not really satisfactory, given the expected lifetime of the resulting structure. It has to “right first time”!

Vibration, sound and electromagnetic interference are all huge unknowns, when it comes to microscope performance. Each manufacturer will provide you with a set of specifications which are “required” for their instrument to meet its guaranteed performance criteria.

In 1936, Otto Scherzer published his famous theoretical paper on the correction of aberrations in round magnetic electron lenses. For fundamental reasons, the aberration coefficients are positive and to introduce negative corrections, the electron optical elements have to produce either charges or poles on the optic axis, or contain a mirror or be a multipole system. In 1997, three papers appeared with actual demonstrations of the correction of aberrations in imaging lenses, probe forming lenses and electron mirrors. It took almost two thirds of a century for this seemingly straightforward development to occur and for the promise of wavelength limited electron imaging to emerge as a practical proposition.

Orientation Imaging Microscopy is currently the most rapidly growing combined metallographic and crystallographic technique today. The first OIM was recorded by Wright in 1991, and published soon after, Adams et al. (1993). The technique is based on the original works on Electron Backscatter Diffraction (EBSD) by Venables and Hariand (1973), and Dingiey (1984, 1987). By 1994 some number of papers on the subject had been published. At the time of writing the authors are aware of over 600 publications that have utilized the technique and there are in excess of 400 systems in use worldwide.

My home microscopy of lake water organisms with my two student microscopes lead to my active participation in Micscape Internet magazine available at the web site http://www.microscopy-uk/mag. An article in Micscape by Dave Walker, http://www.microscopy-uk.org.uk/mag/artian02/toptips8.html. played a critical role in my decision to purchase a Nikon Coolpix 995 for my home microscopy. Dave's article referenced a far more thorough article on fitting a consumer digital camera to older style microscopes: The New Microscopy by Peter Evennett, Proceedings RMS, Vol. 35 (4), Dec 2000.

What in the “real” world does this title mean? Of course, every one using an instrument will insist that his application is in some way unique and therefore not a common, mundane, “real-world” one. The “real-world” for an academically motivated scientist may be quite different from the “real-world” of the commercially motivated scientist. What happens in an asbestos testing lab is quite different from the activities of a consulting group using the microscope to solve industrial problems. Every application is “real world”…but they most certainly may be different.

A large number of natural and synthetic species ranging from virus particles to small polymer beads have been employed over trie years as labels in electron microscopic applications. Perhaps the most useful and versatile of these labels are the colloidal heavy metals. The colloidal labels can be synthesized as round regular spheres in sizes from 1 to 150 nanometers in diameter and thus can be used where molecular and sub-molecular ranges of spatial resolution are required. They are electron “dense” and good emitters of secondary and back-scattered electrons and hence are readily detectable in both scanning electron microscopic imaging systems and transmission electron imaging systems. Larger particles, 10nm and above, can be identified via their shape in force based imaging systems.

“Low Voltage Scanning Electron Microscopy (LVSEM), defined as operation in the energy range below 5 keV” was described by David Joy and Dale Newbury (1) in the previous issue of this journal as being “perhaps the most important single operational mode of the SEM.” In their paper they describe both the advantages and disadvantages of this method.

Ramsey's principle, which was established by Jack Ramsey over many years as a microscopist and microanalyst, is to say: “There is no best way of doing ANYTHING.”

There was a recent thread on the microscopy listserver by John McCaffrey (who hosted the discussion on TEM calibration at the 2001 M&M facility managers session) and Richard Beanland, dealing with the calibration of TEMs. This discussion was prompted by a calibration question from John Basgen, who was looking for more precision and more long-lived calibration specimens. The discussion complements and extends the one of the M&M 2001 managers meeting on EM calibration (Microscopy Today, January/February 2002, issue #02-1), and we are running this separately from that meeting discussion. (MT-ed.)

Two particular questions keep coming up regarding Atomic Force Microscopy (AFM), and we would like to address them here.

The lateral resolution of AFM is a parameter that currently has no accepted definition. The definition used in our lab is “the minimum distance between objects at which you can distinguish distinct objects.” In other words, imagine a surface with two sharp features: upon bringing the two features closer and closer together, at some point only one object is seen. That distance is the resolution limit. It is useful to define “see” as having a dip in height greater than the noise level in the image.

Original transmission electron micrographs illustrating a variety of biological tissues are excellent tools that can be used in the education and examination of first year medical students. Many of these valued micrographs (and the negatives that produced them) date back to the 1960s, to the time when this researcher started a career in microscopy that continues to this day, To avoid returning to the darkroom and laborious photographic techniques, original negatives were scanned to produce micrographs for use in written or laboratory examinations or as images transported into Power Point lecture presentations. Original micrographs also were scanned and provided additional educational materials.