While using casts in place of original bones and teeth for study with the SEM is a rather common practice, periodic updates and introductions of unique casting methods help to keep the process of improving cast quality cumulative, limiting unnecessary repetition of ineffectual procedures. The following is a summary of casting methods that I have synthesized from several published reports as well as some that I have developed independently (e.g., Waters and Savage 1971; Scott 1982; Rose 1983; Gordon 1984; Teaford 1991; Buikstra and Ubelaker 1994; Schmidt, 1998). The study for which I first employed these methods consisted of hundreds of archeologically- derived human teeth dating from about 1,000 to around 10,000 years ago. The study required detailed views of dental surfaces magnified 500X (Figure 1). The casts that I produced routinely had features that were distinct at magnifications of 2.000X and higher.

If you are one of the many people who are currently considering the purchase of a confocal microscope, you may be asking yourself, "How can 1 be sure that the microscope I choose is the right one?"

Before proceeding, take a step back. Ask yourself: "Why use a confocal?" A confocal microscope is, by definition, a microscope which optically "slices" the sample by showing only those details which are at or near the plane of focus. This results in a clearer image than might be possible with a conventional (also called "wide-field") fluorescence microscope - a microscope in which every pixel in every image is corrupted by light from its neighbors. The optical slicing of the sample done by the confocal microscope lets you construct a 3-D representation of the sample that can be very useful for image visualization or analysis.

A thin, flat section of animal or plant tissue will usually adhere to a clean glass surface and stay in place through the common preparative procedures of staining, washing, dehydration and clearing. The adhesion may be due largely to the close contact between two flat surfaces. This allows very weak non-ionic forces (such as van der Waals forces and hydrogen bonds) between individual atoms, to exist in numbers great enough to add up to a strong attraction between slide and section. Ionic attractions, which operate over longer distances, may also exist between the silicate of the glass (negatively charged ions, especially in an alkaline medium) and basic groups of proteins in the tissue (positive ions, especially in an acidic medium). Unfortunately, not all sections are perfectly flat and not all slides are perfectly clean. Even when these conditions are met, there are some staining techniques that are harsh enough to remove the flattest section from the cleanest slide.

The world of scanning electron microscopy seems to spin in such a way that every four years there is a dramatic step forward. Field emission sources (FEG), developed in the late 1960's, started life as a commercial disaster. In spite of the problems, certain manufacturers persisted with the first really user friendly FEG SEM reaching the market in the early 1980s. The FEG has been developed through the 1990's to be, without doubt, the source for SEU. But other advances in SEM performance have added to the instrument's performance, the most recent dramatic step being the introduction of semi-inlens imaging, a technique based upon 1980's dual detector imaging systems.

Tallahassee, Fla. - Dan Zuras admits he never thought he'd be alive when a scientist discovered the microscopic Road Runner image he engraved on a computer chip 16 years ago.

But then again, at the time, who knew the minute circuitry of microprocessors would grace the pages of wall calendars in the 1990s?

Wee pictures of everything from animals to license plates have become the signatures of chip creators, But knowledge of this practive generally stayed within industry circles - until Florida State University researcher Michael Davidson discovered the imprints left by engineers under his highpower microscope.

Scanning Probe Microscopy (SPU) is a versatile tool for the investigations of surfaces. Additionally to the three-dimensional examination of surface topography, local mechanical or electrical properties can be measured1. In this work we present a short contribution on the performance and reliability of piezoelectric transducers in a SPM, which take care of the fine positioning of the tip relative to the sample. Some of the calibration procedures known in literature [cited in 2] are: laser interferometry, scanning a slightly tilted surface, a grid, a crystallographic or artificial step of a known height or by using a reference piezo. To measure slow and fast piezo response simultaneously, we use a non-contact calibration procedure with a high dynamic range (Angstrom to several hundred micrometers) and high frequency range (D.C. to 200 kHz(-3dB)).

In scanning microscopes, like the Atomic Force Microscope (AFM), used in contact mode, scanning begins with engaging the tip with the sample at some contact force, which can be adjusted by the setpoint* (this is common to Digital Instruments' AFMs). It may differ for other brands. For a system that detects the motion of the cantilever with a laser beam, the setpoint basically gives an idea of the voltage difference between the top and bottom photo detectors, When the tip comes into contact, the feedback circuit adjusts the tip deflection according to the required contact force, This is the method commonly followed for the constant deflection method.

Ruthenium tetroxide (RuO4), which is a stronger oxidizing agent than osmium tetroxide (OSO4), reacts well with some of the more polar lipids that fail to show a reaction with OsO4 . it has been demonstrated that the use of RuO4 can overcome the failure of OsC4 to visualize epidermal intercellular lamellae. RuO4 reacts strongly with both saturated and unsaturated lipid molecules, as well as with proteins, glycogen, and monosaccharides. RuO4 fixed membranes appear thicker than those fixed with OsO4 do4.

RuO4 penetrates tissue very slowly and sometimes uneven, patchy preservation may occur. The use of vibratome sections is recommended to optimize penetration of the RuO4 fixative.

Having installed Photoshop 5 after using version 4 for some time, I think that all scientists who believe that the integrity of their imagery is important, understand what Photoshop 5 brings with it: the issue of "color space" or color profiles". Whereas users could rely on the integrity of their image being retained with Photoshop 4, this changes with version 5, and in some cases rather severely. For example, a image bitmap which might represent elemental spatial distribution data should be considered to have a gamma of unity. Photoshop 4 would represent this data for editing via the display monitor's gamma compensation only. That is, the integrity of the pixel values would remain and visual compensation happens between data and display. Photoshop 5, on the other hand, will modify pixel values in accordance with either a desired "working" color space or an anticipated "target" color space.

In recent years there have been a growing number of facilities interested in developing remote access capabilities to a variety of microscopy systems. While certain types of microscopes, such as electron microscopes and scanning probe microscopes have been well established for telepresence microscopy, no one has yet reported on the development of similar capabilities for the confocal microscope.

At California State University, home to the CSUPERB (California State University Program for Education and Research in Biotechnology) Confocal Microscope Core Facility, we have established a remote access confocal laser scanning microscope facility that allows users with virtually any type of computer platform to connect to our system.

In 1968, as an undergraduate, I was first taught how to operate a Philips EM300 TEM that, at the time, was a state-of-the-art 100 keV TEM for materials studies. Last year, I spent time evaluating current state-of-the-art microscopes, f.e., intermediate-voltage, field-emission gun TEMs, from all the major manufacturers. In watching the operators running these latest microscopes, I was struck by the similarity between many of their actions and the same steps that I had learned, so laboriously, 30 years previously.

Most of us have been here more than once: a critical specimen, often the only one of its kind, does not embed properly. Usually the problem is incompletely polymerized resin. After the panic subsides, a limited number of options are left, and if the specimen is irreplaceable, there are no options, other than trying to salvage it the best way you can. I've had this problem before with low viscosity resins, but the following suggestions should work for other resins as well.

First of all, realize that reprocessed specimens are rarely as good as they would be if things went fine the first time around.

Most of the time an air table is not needed for vibration isolation of electrophysiological equipment and microscopes. In fact, an air table can be a liability in that it is likely to pick up air-borne vibrations. This is especially likefy if you have a solid enclosure, as is often used for the construction of Faraday cages used in electrophysiological investigations of vision research. Sound propagation can be particularly annoying, especially at the lower frequencies. Such important details are often forgotten in discussions of this topic.

A good damping table will help reduce the resonances, but still often can't overcome the difficulty posed by sound. One of the best solutions is proper placement of the entire rig: on the slab in the basement in a quiet place with no heavy vibrations from nearby heating, ventilating, and airconditioning (HVAC) and other equipment.

It is extremely difficult to remove artifacts common to eye tissue such as folds, shrinking raisin effect, and parched earth effect. By adjusting our fixation and processing procedures, we attempted to reduce or eliminate these artifacts. We tested the fixatives from various vendors to determine which of them is most compatible with eye tissue and which would eliminate artifacts. We found Pen-Fix (alcoholic formalin; Richard Allen, Richland, Ml) produced optimal fixation (well defined nuclear detail, without bubbling artifact). In similar testing, we found Peel-a-way (Shandon-Lipshaw, Pittsburgh, PA) to be the optimal paraffin for processing and embedding ocular tissues.

The first article reporting the rising incidence of carpal tunnel syndrome in histotechnologists was written by Pearl Gervais and published in the Louisiana Society for Histotechnology newsletter in 1991. Following that article, the growing interest in the number of injuries within the profession prompted a nationwide survey of histotechnologists. The results of that survey appeared in the first part of a three part article published in the Journal of Histotechnology, 18:139,1995. The articles were written by a group of professionals from the University of Michigan. Carpal Tunnel Syndrome (CTS) was used as the model for potential Cumulative Trauma Disorder (CTD).

Learning how to operate the microscope has dominated the TEMteaching process in a way that is perhaps unparalleled by any other common scientific instrument. The TEM column is so complex that the arcane aspects of its manual manipulation become the main points to be learned by the student, rather than the use of the instrument to solve materials problems. In other words, command of the instrument often becomes an end in itself. Such an approach would preach that it is better to be able to produce a striking CDF image that is well aligned and focused than it is to be able to interpret that image in terms of the materials processing responsible for the microstructure!

We are using negative stain or a combination of osmium tetroxide fixation and negative stain to monitor the size homogeneity of lipid vesicle/liposome populations prepared by such techniques as sonication, extrusion, and gel filtration chromatography. Small sonicated vesicles up to about 50 nm in diameter seem sufficiently well preserved in negative stain for adequate size determination, although some flattening upon adherence probably does occur. Larger vesicles such as 100 nm extruded liposomes which contain a large aqueous core are likely to be flattened significantly in negative stain and may be partially stabilized with an osmium tetroxide fixation. The effectiveness of this fixation will in large part depend upon the degree of saturation of the lecithin species.

A large part of the preparation of semiconductor samples for SEM and TEM observations involves the creation of cross sections to expose subsurface defects and three-dimensional structure. A powerful new combination of FIB (FEI Company, Hillsboro, Oregon, http://www.feic.com ) with automated microcleaving technology (SELA, Santa Clara, California, http://www. sela.com ) now offers a comprehensive solution for fast, easy and accurate sample preparation.