Direct Wet Mount

The direct wet mount made from unconcentrated fresh feces is most useful for the detection of the motile trophozoites of intestinal protozoa and the motile larvae of Strongyloides spp. It is also useful for the detection of protozoan cysts and helminth eggs. For fixed feces, the direct wet mount may allow the detection of parasites which do not concentrate well. This method is also useful for the examination of specific portions of feces, such as flecks of blood or mucus. 

Direct wet mounts are prepared by placing a small drop of 0.85% saline toward one end of a glass slide (2 by 3 in. [ca. 5 by 7.5 cm]) and a small drop of appropriate iodine solution (see below) toward the other end. With an applicator stick, a small portion of specimen (1 to 2 mg) is thoroughly mixed in each diluent, and a no. 1 cover slip (22 mm) is added. The density of fecal material should be such that newspaper print can be read with difficulty through the smear. The material should not overflow the edges of the cover slip. Grit or debris may prevent the cover slip from seating and may be 

For the examination of wet mounts, the light of the microscope must be properly adjusted. To achieve optimal resolution, the condenser should be centered and focused for Kohler illumination (racked up). To achieve contrast of the objects in the field, light intensity is diminished with the iris diaphragm of the condenser rather than by lowering the condenser. 

A solution of buffered methylene blue (pH 3.6) may be used as a vital stain for the examination of fresh specimens for protozoa. The wet mount is prepared as described above, with buffered methylene blue substituted as diluent and 5 to 10 min allowed for the dye to become incorporated in the organisms before examination. Organisms become overstained in 20 to 30 min. 

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The three principal microscopic examinations performed on stool specimens are direct wet mount, wet mount after concentration, and permanent stain. Although each examination can contribute to diagnosis, the yield of some methods is small with certain kinds of specimens. As a minimum, formed specimens should be examined by a concentration procedure. Soft specimens should be examined by concentration and permanent stain, and, if submitted fresh, by direct wet mount. Loose and watery specimens should be examined by wet mount and permanent stain. If specimens are received in fixative and the consistency is not known, concentration and permanent stain should be performed. Other examinations may be helpful. Special procedures which may assist in the diagnosis of specific parasites are noted below in discussions of the parasites. 

Type of specimen Direct wet mount Method Concen- tration Permanent stain... 

Fluids such as tissue aspirates, cyst fluid, bronchial washings, cerebrospinal fluid, pleural fluid, and peritoneal fluid can be examined directly, or they can be centrifuged and the sediment examined by wet mounts or stains (or both), depending on the parasite suspected, as described above for abscesses or tissue. 

Direct examination of tissue or body fluids believed to be infected can provide simple, rapid information to the clinician. Microscopic examination of wet-mount specimen preparations can provide valuable information regarding potential pathogens. Applications of this procedure with or without staining preparations include direct examination of sputum, bronchial aspirates, scrapings of mucosal lesions, and urinary sediment. The Gram stain is one of the... 

In the construction of the wet oxidation unit, several areas of safety were considered. Of utmost importance was that of personal safety. Since this type of operation demands the use of high pressures and temperatures, operator contact with the high pressure vessels had to be limited. To accommodate this criterion, a barrier was constructed to shield the operator from any unforeseen releases from the reactor. This barrier was constructed from 1/4 inch steel and is desig ied in a manner that will fully contain any releases. This barrier is also equipped with two explosion vents to direct the force of any explosions away from the main walls and into a safe area. To further maximize personnel safety, all operator assisted controls are mounted on the outside of the unit. 

A small, hot, pointed flame from the handlamp is now directed precisely on the rotating scratch and heating continued till the flame begins to show a yellowish colour. The flame is immediately removed and a wet cloth applied to the heated scratch line. The tube will crack cleanly round the line. Some practice will be required to make a straight mark. The author uses a diamond point mounted on a rod attached to the tool bar, as shown in Fig 4.8 (p. 36). The heat mugj... 

Both the heat and mass transfer coefficients are functions of air velocity. However, at air speeds greater than about 15 ft/s (4.5 m/s), the ratio h kgis approximately constant. The wet-bulb depression is directly proportional to the difference between the humidity at the surface and the humidity in the bulk of the air. In the wet- and dry-bulb hygrometer, the wet-bulb depression is measured by two thermometers, one of which is fitted with a fabric sleeve wetted with water. These thermometers are mounted side by side and shielded from radiation, an effect neglected in the derivation above. Air is drawn over the thermometers by means of a small fan. The derivation of the humidity from the wet-bulb depression and a psychrometric chart are discussed later. 

Samples for SAXS were prepared in sealed vials as reported elsewhere (2). Two Kapton (polyimide) films (7.5 pm thick) were buffed in the y-direction with an ethanol-wetted tissue paper. About 100 mg of sample were molten at 55°C to a liquid crystal and transferred to a tense, fixed Kapton film. Before cooling to below 35 °C, another Kapton film was put over the sample and both tense films were gently rubbed against each other at -0.5 mm/s in the y-direction for -10 s. Within three minutes the sandwiched sample was mounted in a hot copper block with a hole for the beam, and annealed at 58 1 °C for 30 min prior to the start of a 22-h exposure, during which annealing was continued. 

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