It's always refreshing to read about two old techniques being combined in a novel way to yield new information. Osamu Ohtani and Yuko Ohtani recently accomplished this. Louis Ranvier probably introduced the use of silver nitrate as a histology stain over a century ago. Whereas Ranvier is best known for describing nodes along the nerve fiber, he also demonstrated that silver nitrate stained endothelial cells, allowing their borders to be clearly visualized. In the 1970's, Takuro Murakami first used the scanning electron microscope (SEM) to examine corrosion casts of the vasculature. Much of what we currently know about the microarchitecture of blood vessels has been discovered using this technique.

One of Murphy's Laws says that whenever something is published, it is immediately out of date. Project MICRO'S “Microscopy for Children: a Bibliography”, which was distributed with the December issue of this publication is no exception. I have been contacted recently about a few CD-ROMs that will interest many readers. Since the web version of the bibliography (URL below) will not be updated for a while, I am providing listings as follows.

The Scanning Electron Microscope (SEM) with associated Energy Dispersive Spectrometer (EDS) is commonly used to characterize the structure and elemental composition of a wide variety of materials of forensic significance. When these materials are extremely limited in size, SEM/EDS is often the only suitable method for characterization available in forensic science laboratories.

Because of the inability to access SEM/EDS data from large numbers of materials, the Federal Bureau of Investigation (FBI) laboratory believes that this discipline has not realized its full potential. The usefulness of SEM/EDS has been limited by the inability to archive spectra within a utility having a true database architecture. The FBI Laboratory has designed such an X-ray database, consisting of storage, query, and display utilities unique to X-ray spectroscopy.

Several years ago Honegger (1985) described a simple technique for removing plant cell protoplasm in order to reveal details of interfaces between plant cells and fungal structures. This technique involves the use of Ariel a commercially available washing powder (Proctor and Gamble) containing a Bacillus substilis derived protease. We since have used this technique with excellent results to examine not only the morphology of fungal haustoria inside leaf cells of various host plants but also features of the inner surface of the host cell wall with scanning electron microscopy (SEM). Here we describe the procedure we have used to prepare samples for study and provide examples of the types of images we have obtained from our samples.

This article was originally written to respond to a discussion on the Microscopy Listserver found on the Internet concerning backfilling an electron microscope with nitrogen versus laboratory air. It was expanded to include general vacuum comments, suggestions, and techniques that could be of possible value to the working microscopist.

Recently, there was a thread on the microscopy listserver about focusing TEMs, in particular whether to focus at crossover, or at the illumination level used for recording images. When setting the image focus there are a number of problems that may complicate matters.

Many scanning electron microscope (SEM) laboratories use double sticky carbon tape applied directly to SEM stubs as samplers for small particles. The SEM samplers used by law enforcement to test the hands of a suspect for gunshot residue (GSR) are constructed in this manner.

A few years ago, during a presentation at a professional meeting, I presented spectra of particles that were mounted on carbon double sticky tape that was applied directly to the aluminum- alloy SEM stubs. After the presentation a colleague posited that small peaks of copper, which appeared in some of my spectra, were due to a copper support frame for the backscatter detector at the top of the SEM chamber and not the particles. Indeed, I have frequently noticed small peaks of copper in spectra of particles where these should not be present.

Questions have arisen recently on the Microscopy Listserver about the best way to decapsulate integrated circuit chips. Here is the method that has been developed at the Dallas Device Analysis Operation of Texas Instruments, inc., and is used by many laboratories here. We find that it works very well.

This note concerns two very important parts of most beam instrument systems; diffusion pumps and water chillers. As we'll see below, the two can be intimately connected.

Many SEMs, TEMs and other electron beam instruments contain one or more diffusion pumps as part of their vacuum systems. These are usually vertically-oriented cylindrical objects, perhaps 30 cm high, wrapped in several turns of copper tubing. They are usually placed behind or below the instrument's column, and typically handle high vacuums for tungsten filaments, or backing for ion pumps with other emitter types. Generally, these units are fairly maintenance-free; a change of oil every few years may be all that is required.

A question on the Microscopy Listserver concerned using an FESEM to examine a thin, thermally-evaporated gold film on single crystal germanium. It is always a difficult problem to find small surface details or textures on a smooth surface in the SEM. A surface without visible topography looks the same whether it is in or out of focus, and so the method to make sure the surface is in focus is a slow, iterative one.

My researchers like to give me a one inch square of highly polished steel or titanium and ask me to find and analyze the five tiny inclusions somewhere in the middle. If there is a particular feature or area that I need to examine, I find that area by eye or under a low power, binocular light microscope and mark it with a fine, red felt-tip pen.

Over the past decade the Atomic Force Microscope has been utilised in a myriad of applications across many fields of research and industry. One area that has been of particular interest is the measurement of small scale forces. The AFM is capable of measuring electrostatic and van der Waals forces with high precision based on small deflections of the AFM cantilever.

The forces between colloidal particles dominate the behaviour of a great variety of materials. The AFM has been extensively used to measure the forces between planar surfaces and individual colloid particles. One of the key driving forces for such experiments and the corresponding theoretical framework that has ensued is the ease of use of standard AFM tips for such measurements.