Polarizing light microscopy

Microscopy (qv) plays a key role in examining trace evidence owing to the small size of the evidence and a desire to use nondestmctive testing (qv) techniques whenever possible. Polarizing light microscopy (43,44) is a method of choice for crystalline materials. Microscopy and microchemical analysis techniques (45,46) work well on small samples, are relatively nondestmctive, and are fast. Evidence such as sod, minerals, synthetic fibers, explosive debris, foodstuff, cosmetics (qv), and the like, lend themselves to this technique as do comparison microscopy, refractive index, and density comparisons with known specimens. Other microscopic procedures involving infrared, visible, and ultraviolet spectroscopy (qv) also are used to examine many types of trace evidence. 

MDHS 77 Asbestos m bulk materials - Sampling and identification by polarized light microscopy (PLMj... 

XPD [18]. Similarly, mineral impurities in talc were analyzed by polarizing light microscopy, differential thermal analysis, and XPD [19]. It must be recognized, however, that small amounts of crystalline impurities (usually <0.5% w/w) may not be detected by XPD. In case of noncrystalline impurities, mrch higher concentrations may be nondetectable. 

The starting system is achiral (plates at 90° with isotropic fluid between), but leads to the formation of a chiral TN structure when the fluid becomes nematic. In this case, enantiomeric domains must be formed with equal likelihood and this is precisely what happens. The size of these domains is determined by the geometry and physics of the system, but they are macroscopic. Though the output polarization is identical for a pair of heterochiral domains, domain walls between them can be easily observed by polarized light microscopy. This system represents a type of spontaneous reflection symmetry breaking, leading to formation of a conglomerate of chiral domains. 

Vukjovic et al.199 recently proposed a simple, fast, sensitive, and low-cost procedure based on solid phase spectrophotometric (SPS) and multicomponent analysis by multiple linear regression (MA) to determine traces of heavy metals in pharmaceuticals. Other spectroscopic techniques employed for high-throughput pharmaceutical analysis include laser-induced breakdown spectroscopy (LIBS),200 201 fluorescence spectroscopy,202 204 diffusive reflectance spectroscopy,205 laser-based nephelometry,206 automated polarized light microscopy,207 and laser diffraction and image analysis.208... 

In microscopy, an azimuth is an angle measured relative to a north-south axis of the microscope tube. Normally, the primary north-south axis divides the visible field into left and right sides and corresponds to a position of 0° on the first polarizer, usually below the substage condenser. Be careful if the orientation of the visible field has been altered by microscope accessories (such as cameras), which is why Bennett (26) defined the 0° axis relative to the stand of the microscope. From the 0° position, we follow the convention used in the mathematics of polar coordinates, moving counterclockwise to increment the angles. Points of the compass also are used to describe the orientations of components used for polarized light microscopy, and are abbreviated to N, S, E, and W. 

Polarized light microscopy, 26 474-478 Polarized light microscope (PLM), 26 469-470, 477, 484 Polarizer, 26 470... 

In coronal caries, the enamel of the tooth crown is affected. With lasting caries, the lesion deepens and acquires a conical shape. In polarized light microscopy, zones with different mineral densities can be distinguished, such as the lesion body and the mineralized surface layer... 

McCrone, W. (1978). Identification of asbestos by polarized light microscopy, pp. 235-248. In C. C. Graved, ed. Workshop on Asbestos. Spec. Pub. No. 506. National Bureau of Standards, Washington, DC. 

Sugano, K., Kato, T, Suzuki, K., Keiko, K., Sujaku, T. and Mano, T. (2006) High throughput solubility measurement with automated polarized light microscopy analysis. Journal of Pharmaceutical Sciences, 95, 2115-2122. 

Polarized light microscopy is the study of the microstructures of objects using their interactions with polarized light [1,2,23-27,31-33]. The method is widely applicable to polymers [34] and to liquid crystals [34-37]. The polarizing micro-... 

Gout can be diagnosed by the presence of negatively birefringent monosodium urate crystals in aspirated synovial fluid examined by polarized-light microscopy. Here, crystals are within polymorphonuclear leukocytes. 

Microscopy plays a key role in examining trace evidence owing to the small size of the evidence and a desire to use nondestructive testing techniques whenever possible. Polarizing light microscopy is a method of... 

The structure (e.g., number, size, distribution) of fat crystals is difficult to analyze by common microscopy techniques (i.e., electron, polarized light), due to their dense and interconnected microstructure. Images of the internal structures of lipid-based foods can only be obtained by special manipulation of the sample. However, formation of thin sections (polarized light microscopy) or fractured planes (electron microscopy) still typically does not provide adequate resolution of the crystalline phase. Confocal laserscanning microscopy (CLSM), which is based on the detection of fluorescence produced by a dye system when a sample is illuminated with a krypton/argon mixed-gas laser, overcomes these problems. Bulk specimens can be used with CLSM to obtain high-resolution images of lipid crystalline structure in intricate detail. 

McCrone, W. C. McCrone, L. B. Delly, J. G. Polarized Light Microscopy, McCrone Research Institute Chicago, IL, 1984. 

Light microscopy has been used in a number of contexts to characterize block copolymer morphology. For crystalline block copolymers, spherulitic structures that result from organization of crystalline lamellae can be examined using microscopy. In solutions, polarized light microscopy can reveal the presence of lamellar and hexagonal-packed cylindrical micellar phases. Cubic micellar phases are optically isotropic, and consequently cannot be distinguished from sols only on the basis of microscopy. 

The structure of hard gels is best elucidated using SAXS or SANS because the periods of the ordered structures are on the scale 10-100nm. In addition to tube inversion and rolling ball viscometry, which are sensitive to yield stress, the formation of a hard gel can be identified by other techniques. These include DSC (gelation is an endothermic process), NMR (via transverse relaxation time, T2, measurements), polarized light microscopy and rheometry. 

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