Microscopical examination

Tlrese metlrods may be applied to on line wire surface testing where conventional procedures are inadequate, such as tire stylus metlrod, due to the specimen diameter or microscopic examination. 

In summary, it has become quite clear that contact between two surfaces is limited to a small fraction of the apparent area, and, as one consequence of this, rather high local temperatures can develop during rubbing. Another consequence, discussed in more detail later, is that there are also rather high local pressures. Finally, there is direct evidence [7,8] that the two surfaces do not remain intact when sliding past each other. Microscopic examination of the track left by the slider shows gouges and irregular pits left in the softer metal... 

Acryhc and modacryhc fibers are sold mainly as staple and tow products with small amounts of continuous filament fiber sold in Europe and Japan. Staple lengths may vary from 25 to 150 mm, depending on the end use. Eiber deniers may vary from 1.3 to 17 dtex (1.2 to 15 den) 3.2 dtex (3.0 den) is the standard form. The appearance of acryhcs under microscopical examination may differ from that of modacryhcs in two respects. Eirst, the cross sections (Eig. 1) of acryhcs are generally round, bean-shaped, or dogbone-shaped. The modacryhcs, on the other hand, vary from irregularly round to ribbon-like. The modacryhcs may also contain pigment-like particles of antimony oxide to enhance their flame-retardant properties. 

Although visual and microscopical examination, together with simple manual tests, are stiU the primary methods of identification, there are many new sophisticated instmmental methods available based on chemical and physical properties. These methods are able to distinguish between closely related fibers which differ only in chemical composition or morphology. 

Visual and Manual Tests. Synthetic fibers are generally mixed with other fibers to achieve a balance of properties. Acryhc staple may be blended with wool, cotton, polyester, rayon, and other synthetic fibers. Therefore, as a preliminary step, the yam or fabric must be separated into its constituent fibers. This immediately estabUshes whether the fiber is a continuous filament or staple product. Staple length, brightness, and breaking strength wet and dry are all usehil tests that can be done in a cursory examination. A more critical identification can be made by a set of simple manual procedures based on burning, staining, solubiUty, density deterrnination, and microscopical examination. 

Microscopical Examination. All fibers have distinguishing features which either allow outright identification or classification iato narrower grouping for specialized analysis. Fiber cross sections are particularly usehil for identification. 

When the acetylation is completed, microscopic examination of the solution should reveal no undissolved residues. The reaction is terrninated by adding water to destroy the excess anhydride and provide a water concentration of 5—10% for hydrolysis. A 10—25% cellulose acetate concentration is typical. 

Structural Analysis. Some of the optical techniques are also used for stmctural analysis. Microscopic examinations of metallurgical cross sections or of sections through the paint layers of a painting are indeed stmctural examinations, as is ir reflectography. 

Microscopic examination of cross sections through the paint layers gives definite information regarding the paint-layer sequence in the area from which the sample was taken (31,66). This information illustrates the artist s use of underlayers and glazes, superposition of compositional elements, and changes in composition. 

Examination. Microscopic examination (123) can identify the fibers present ia the pulp (124). Inks, watercolor pigments and media, etc, are analyzed similarly to the pigments and media for paintings. However, sample removal tends to be far more disfigutiag and hence constitutes an even more restrictive factor. Watermarks are studied with the aid of beta-radiography. Examination ia iafrared illumination can assist ia the reading of documents of which the ink has faded. 

Spices are natural agricultural products and exhibit a range of variations of many specific characteristics. The most important quaUty assessment is the subjective physical observation of the whole or ground spice by an expert. The macroscopic and microscopic examination of spice is the criterion for the continued analysis of the product to determine adherance to specifications. 

The primary use of EIA when it was first developed was for histological labeling and localization of specific cell macromolecules. Eor example, enzymes labeled with peroxidase were used to locate specific cellular compartments and stmctures for microscopic examination. The flexibiUty of EIA was recognized quickly and it was adapted for use as a laboratory assay. 

The function of the essential oil in the plant is not fully understood. Microscopic examination of plant parts that contain the oil sacs readily shows their presence. The odors of flowers are said to act as attractants for insects involved in pollination and thus may aid in preservation and natural selection. Essential oils are almost always bacteriostats and often bacteriocides. Many components of essential oils are chemically active and thus could participate readily in metaboHc reactions. They are sources of plant metaboHc energy, although some chemists have referred to them as waste products of plant metaboHsm. Exudates, which contain essential oils, eg, balsams and resins, act as protective seals against disease or parasites, prevent loss of sap, and are formed readily when the tree tmnks are damaged. 

In a general way, the identification of asbestos fibers can be performed through morphological examination, together with specific analytical methods to obtain the mineral composition and/or stmcture. Morphological characterization in itself usually does not constitute a reHable identification criteria (1). Hence, microscopic examination methods and other analytical approaches are usually combined. 

D. H. Campbell, Microscopical Examination and Interpretation ofiPortland Cement and Clinker SP030, Pordand Cement Association, Skokie, lU., 1986. 

Careflil examination of a piece of coal shows that it is usually made up of layers or bands of different materials which upon microscopic examination are distinct entities distinguishable by optical characteristics (10—12). The study of the origin, composition, and technological appHcation of these materials is called coal petrology, whereas coal petrography involves the systematic quantification of the amounts and characteristics by microscopic study. The petrology of coal may involve either a macroscopic or microscopic scale. 

A.STM B487, Std. Test Methodfor Measurement of Metaland Oxide Coating Thickness by Microscopical Examination of a Cross Section, American Society for... 

Evaluation of attack if other than general, such as crevice corrosion under suppoi t rod, pit depth and distribution, and results of microscopic examination or bend tests... 

Oxygen corrosion involves many accelerating factors such as the concentration of aggressive anions beneath deposits, intermittent operation, and variable water chemistry. How each factor contributes to attack is often difficult to assess by visual inspection alone. Chemical analysis of corrosion products and deposits is often beneficial, as is more detailed microscopic examination of corrosion products and wasted regions. 

Microscopic examinations revealed that the cracks were unbranched and transgranular, t3q)ical of corrosion-fatigue cracks. These examinations also... 

Microscopic examinations revealed tight, unbranched, transgranular cracks originating on the external surface. Many of these cracks originated at shallow pockets of corrosion. 

Because wastage is usually slight, identification by visual observation alone is difficult microscopic examination is usually required. Layer-type dealloying commonly occurs. Plug-type denickelification attack has never been observed at this laboratory. Surfaces have a reddish color due to the accumulation of denickelified metal. 

Microscopic examinations revealed iron oxide coatings on the plate that interfered with metallurgical bonding to the weld metal. 

An irregular trough of metal loss is apparent along the circumference of the ring (Fig. 16.4). Metal loss is severe near the nozzle holes (Fig. 16.5). The corroded zone is covered with light and dark corrosion products and deposits. Analysis of these revealed substantial quantities of copper and zinc. Microscopic examinations revealed exfoliation of the aluminum ring in corroded regions. 

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