The scintillator Is a part of the electron collection system in most SEMs and other types of electron imaging systems. Without a properly functioning scintillator, images may be noisy, weak, or exhibit other signs of degradation.

There are three types of scintillators generally used in the SEM: organic/polymeric, phosphor powder, and crystalline (single or poly).

Plastic scintillators are currently used less frequently, mainly because they are subject to radiation damage (i.e., short lifetime). This type of scintillator has the shortest decay time (~2.2 - 5 ns) and very low noise. We still have many customers who prefer this type of scintillator even though they have to change it more frequently (∼2 - 6 month lifetime with average use is our experience).

The surface of printed paper has been examined through a fully automated attenuated total reflection (ATR) mapping technique. Automated z-axis control was utilized to bring the sample into contact with the ATR objective in a reproducible manner and an integrated mapping stage was used to position the sample. A force sensing device, the Contact Alert, was used to ensure optimal contact between the sample and internal reflection element Global manipulations of the resultant data revealed compositional differences attributed to the printed ink, carbonate and cellulose distributions. These differences were clearly evident in the infrared, but not discemable in the visible. The bulk filler Kaolinite was identified as a post processing contaminate as well as a trace mixture of Dioctyl Phthalate and an aromatic acrylate.

Pioloform F (Wacker Chemie Co., Munich, Germany) is an excellent plastic for use as a support film for electron microscopy. The advantages of Pioloform F are high mechanical and thermal stability, and low material bulk (Stockem, 1970). Because of these properties, thinner films than Formvar or collodion may be used and remain stable under the electron beam without subsequent stabilization by carton coating. Thin support films of gray interference color are prepared by dissolving 0.5 grams of Pioloform F powder in 100 milliliters of anhydrous chloroform (Stockem, 1970), using the dip method described by Reimer (1967).

Wood cells have strong autofluorescence in a wide wavelength band due to lignin in the cell walls. The detection of microorganisms in wood is very difficult when using fluorescent microscopy because of interferences. We have recently developed fluorescent staining techniques to differentiate fungal hyphae from wood cell walls (Singh, et al., 1997; Xiao, et al., 1997). This study was aimed at developing fluorescent techniques to visualize bacteria in wood using confocal laser scanning microscopy (CLSM). Nitrobenzoxadiazole glycerophosphoethanolamine (NBD-PE, Molecular Probes), a widely used membrane probe which accords strong fluorescence upon lipids, was compared with glutaraldehyde which had proved useful in our initial attempts to visualize fungal hyphae in wood because of the cell auto fluorescence it causes (Singh et al., 1997).

Microscopists frequently find that they need to regulate temperature during the course of their experiments. This is especially true for cell biologists working with living cells, Excellent commercial equipment does exist to control the stage temperature of light microscopes, and regulation by such devices is tightly controlled; ± 0.1°C is routinely reported. However, such equipment is often quite expensive and may not provide the investigator with the certainty that the experiment is being performed at exactly the temperature reported by the readout of the thermoelectric control, since the temperature sensor is often at a distance from the actual site of observation. The temperature also varies considerably from the stage heater/cooler to the critical, observed portion of the slide.

The application of confocal laser scanning microscopy (CLSM) in the studies of biological materials is rapidly expanding because of the opportunity to produce sharp, high resolution images through optical sectioning and computer assisted 3-D reconstruction. At our institute CLSM is being used in a wide range of forestry and wood science studies.

Recently we investigated the potential usefulness of CLSM in characterizing biologically degraded wood. The following are images produced from an archaeological wood which has been buried in a wet environment (rice field) for nearly 2,000 years in South Korea and is apparently degraded by bacteria. In an attempt to develop suitable techniques which can be used for routine examination of fragile degraded wood with CLSM, we have compared two different embedding methods for their suitability in preserving the integrity of cells. The embedding media are paraffin wax and LR White resin.

Liquid propane and similar coolants are used in the rapid freezing of biological specimens. These coolants form explosive gas mixtures with air with a 14,000-fold increase in volume over that of the liquid. The liquefied gases have high vapour pressures and, unless they are maintained below their flashpoint, the vapour above them will reach ignitable concentrations. The flashpoint of liquid propane is -104°C. Ethane has a higher vapour pressure, and vapour mixed with air above liquid ethane can be ignited at a coolant temperature of -130°C. The danger is minimized if the coolant is maintained near its freezing point and under a nitrogen atmosphere, in a fume cupboard. Liquid nitrogen evaporates to a 690-fold increase in volume at room temperature. It is important to ventilate the working area, especially when cryo-sectioning in a small room, otherwise there is a possibility of asphyxiation.

If you can recognize a robin or a banana by sight, you should be able to recognize single particles of coal, cement or gypsum when the microscope magnifies them to an equivalent size. This is the thesis of those who identify small particles by microscopy. No other microanalytical method identifies such small samples of such diverse substances so quickly.

Single particles of almost any substance - animal, vegetable, mineral, industrial byproduct, raw material, corrosion product, flyash - can be identified in a few seconds to a few minutes by a microscopist trained in particle identification. The particle must be at least 2 to 3 microns in diameter and 10 picograms or 10-11 gram in weight for identification by light microscopy.

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.

Microscopists have special challenges when presenting image data to audiences, Issues such as image size, resolution, and labeling are related to the format of the presented image. Contact prints, transparencies, 35 mm film, and projected video of digital images are some of the output options possible for microscopy presentation. This brings us to a question which Jonathan Krupp of the University of California, Santa Cruz, recently posed to the Microscopy listserver;

Silicone rubber embedding molds may be inexpensive In North America, but are not necessarily so elsewhere in the world. Further, commercial molds are available only in standard sizes and only with standard sizes and shapes of cavities for specimen embedding, If, however, one needs to embed specimens of n on standard size or shape, wants more embedding cavities per mold than usually available, or is working where commercial molds are expensive or not easily available, then all is not lost, Embedding molds for specimen blocks can easily be made in the lab from silicone rubber. Further, making embedding blocks allows the use of different silicone rubbers which would be of value with unusual embedding resins, or when embedding must be done in unusual environments (such as extreme cold or heat).

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.

Negative staining is a simple yet extremely useful procedure for examining nanometer-sized specimens such as intact microorganisms (viruses and some bacteria), subcellular components, and even nonbidogical particulates. It is a well established procedure, with extensive literature in many disciplines (Hayat and Miller, 1990). Although numerous variations exist, the basic procedure involves placing the specimen and stain onto a grid containing a substrate - usually plastic with or without a carbon backing. The stains consist of salts of heavy metals such as tungsten, uranium, or molybdenum which surround and often penetrate the specimen. Afier drying into an amorphous, glass-like background, the stains provide contrast based upon differential thickness.

The bubbled, popcorn or moth-eaten appearance of nuclei hampered accurate microscopic evaluation of bone marrow and lymph node biopsies. This artifact was also noticed in skin biopsies, but had little bearing on diagnosis. All aspects of specimen handling processing and staining were scrutinized and improved morphological detail was attained only after blocks were recut and allowed to dry completely before staining.

Anybody who has ever worked with cells or tissues in culture knows that the dish in which to grow and look at the specimen can be of crucial importance to the results obtained, With the growing importance of live cell microscopy, be it simple phase contrast or sophisticated multilabel confocal laser scanning microscopy (CLSM), people have been looking for dishes that combine optimal growth conditions with optimal optical properties. As follows, I will describe a solution that has worked for us with a multitude of different cells, tissues and applications. Apart from that, it is cheap and easily self-made.

The bottom of a standard 35 mm plastic ceil culture dish has a hole of ca. 10 mm drilled into it and a coverslip glued to its downside to cover the hole. For a glue we usually use Sylgard, an inert silicone elastomer (Dow Corning) or melted paraffin if we intend to take off the coverslip again.

A few weeks ago, a person posted an interesting question on an internet microscopy mailing list: what is the difference between histogram stretching and histogram equalization when applied to microscopy images? The following is a short intuitive review which compares the two. Since this is a short and general description, I will gloss over some details and make some generalizations which may not be true in all cases and implementations.

The first thing to remember is the basic purpose of contrast enhancement. The idea is simple, In a grayscale (black and white) image you are simply trying to take two levels of gray that are close together, and thus visually similar, and move them apart so you can better see the difference between them. You can think of grayscale values in an image as beads on a string, Contrast enhancement simply moves all or some of those beads farther apart.

Confocal microscopy has gained great popularity in biology and medical research because of the ability to image three-dimensional objects at greater resolution than conventional optical microscopes. In a typical Laser Scanning Confocal Microscope (LSCM), the specimen stage is stepped up or down to collect a series of two-dimensional images (or slices) at each focal plane. Conventional light microscopes create images with a depth of field, at high power, of 2 to 3 μm. The depth of field of confocal microscopes ranges from 0.5 to 1.5 μm, which allows information to be collected from a well defined optical section rather than from most of the specimen. Therefore, due to this “thin” focal plane, out of focus light is virtually eliminated which results in an increase in contrast, clarity and detection.

A long time ago, we ciid some work on RBC's from muscular dystrophy patients, We found that the cells are very sensitive to pH, salt concentration, glass, and other things (maybe including the moon???), Low pH, increased salt, especially NaCl, and sitting in a glass tube or on a glass slide unfixed would cause echinocyte formation.

We got around the problem by drawing the blood and then IMMEDIATELY dropping (drop by drop) blood samples into 1% glutaraldehyde in phosphate buffer, pH 7.4 (not PBS). You can use a Maunsbach formula, where 0.135 U P04 gives 300 milliosmoles, or 0.1 M P04 plus sucrose (try 1.8 % sucrose). Test the osmolarity of the buffer; it should be 300 ± 10 or so. The final osmolarity of the buffered fix will be 400 milliosmoles; 300 from the buffer and 100 from the glutaraldehyde! The fix should be room temperature (not cold) when the blood is added. It can be stored refrigerated.