There are three ways that objects can react to microwave energy within a microwave cavity:

1. 1. They can absorb microwave enengy. This is the case with all polar molecules (substances with positive and negative ionic poles). Examples include water, alcohols and biological specimens. Objects which absorb microwave energy will get hot as a result. The total amount of microwave absorbing material within the miaowave cavity is called the “load.”

2. 2. They can reflect microwaves. This is the case with metals. The function of the medal walls which make up a microwave cavity is to keep the microwave energy within the cavity. The metal walls themselves will not get hot.

3. 3. They can be “microwave-transparent.” This is the case with many non-polar molecules, such as paraffin and many plastics. Objects which ane microwave transpanent will heet very poorly in a microwave.

A number of years ago, I produced a Christmas card which featured a snowflake in the unusual form of a Christmas tree. To enhance the suggestion of “evergreen”, I photographed it by transmitted light with a green filter (Wratten No. 58) in the light path. It has been almost twenty years since the card appeared, and in that time I have had many occasions to project the original 35-mm transparency, When I do show it, I mention that particular snowflake was captured during a snowfall in Chicago on January 17, 1971.

Chemical microscopy techniques were once a major source of information for scientists who wanted to detect the presence of metals in samples. Many microscopists used such techniques, which, when properly applied and appropriate checks for interferences made, could conclusively prove the presence of small quantities of specific metals.

The fact that the identification could be conclusive for trace amounts following relatively simple and cheap processes, and that visual evidence resulted, made these techniques quite robust, Chamot and Mason's lest “Handbook of Chemical Microscopy” is held to be a definitive resource for these techniques1. With the development of absorpilon and emission based spectral analytical techniques, the application of chemical microscopy techniques dwindled, perhaps because the skills needed by analysts using spectral techniques were to be more rapidly acquired than those involving microscopy,

Rapid freezing of biological samples for subsequent processing and examination in the TEM has been around since the 1960's. Freezing in general, is advantageous because it can provide an instantaneous cessation of all biological activity and hall ultrastructural rearrangement The freezing ‘fixes” biological structures in water ice until such time that the ice can be substituted for a chemical fixative. Freezing is typically conducted at liquid nitrogen temperatures (-196°C), and freeze substitution (FS) is then carried out over days to weeks on dry ice (-80°C) (Severs el. al., 1995).

It is well known to electron microscopists working in the field of materials structure research that the importance of transmission electron diffraction patterns (TED) is: (i) establishing the crystallographic orientation correlations revealed during the practical observation of multiphase specimens and (ii) the knowledge of exact crystallographic orientation of a single crystal area in the specimen relating to image contrast interpretation.

The world of electron microscopy is in a period of transition from acquiring images on film to acquiring images digitally, using CCD cameras, for example. It would be useful to knew how much information there is on a piece of film, in order to know how film compares with digital methods and to be able to make good judgements on the optimum moment to change from one technology to the other.

This is an attempt to use simple arguments to estimate just how much information there is in an image exposed on film in the transmission electron microscope, the main reason for addressing this issue Is that, while many people are affected by it there seems to be little agreement on the answer.

From time to time, a stable but adjustable voltage source can be quite handy. This article was prompted by a request for a replacement for mercury battery collage references which are not only difficult to find, but are rot environmentally friendly. Another application could be powering a 3 to 9 volt disk-man (or whatever) from a nominal 12 volt source such as an automobile. In fact, the circuit can be set to supply any collage From 3 to 38 volts.

Uranium compounds, especially uranyl acetate, have been widely and routinely used as transmission electron microscopy centrist stains for biological materials since 1958. Those of us who do TEM of biologicals use small quantities of uranyl acetate, nitrate, formate, sulfate and perhaps other uranium compounds almost daily and therefore keep inventories of these salts and their solutions.

In the 1980's growing concerns about medical and research wastes entering regional dump sites prompted state radiation officials in Oregon to begin tightening the regulations for monitoring and controlling all radioactive substances including the uranium compounds commonly used in processing biological specimens for TEM.

Let's face it. Looking through a microscope is not what our bodies were built for, and looking through a microscope for an extended period of time requires an unnatural rigidity of the body. You're not moving around, even a bit, as you normally would. The result can be cramped muscles, especially in the neck and shoulders, and a whole body fatigue Hi at can make 10:00 AM feel like 5:03 PM. The solution is correct posture and a proper arrangement of microscope, chair, and body.