Polarizing microscopy definition

Polarized microscopy can be used as one of several methods for the assessment of liquid-crystalline structure. Because of its simplicity it deserves to be used, but it is equally clear that the X-ray diffraction methods, particularly on aligned samples, provide more definite answers. 

The demonstration of amyloid protein in a tissue biopsy specimen by staining with Congo red and examination by polarized light microscopy is required for a definitive diagnosis. 

Whilst the early reports of intermediate phases concerned systems with reversed curvature [73-76] these were for surfactants where some residual short range order in the polar groups was probably present. There are few definitive reports of fully molten intermediate phases with reversed curvatures. In fact the pattern of how intermediate phases replace the normal bicontinuous cubic phase as alkyl chain size increase only became recognized as systematic studies on homologous series were carried out [37, 66], Here it has required a combination of microscopy, multinuclear NMR and X-ray diffraction to elucidate the structures. Such studies on reversed phases have yet to be carried out, particularly where small variations in alkyl chain structure are made. 

The above definition of a homogeneous microstructure does not pertain to pores and structural components which may be visible by contrast differences in optical microscopy with polarized light. As a consequence, glass-like carbon with visible pores is still an agranular carbon. The same is true, for instance, for pyrolytic carbon with preferred orientation, such as conical or lamellar structures, visible in optical microscopy with polarized light. The use of the term agranular carbon is not restricted to bulk materials of a minimum size. Only particulate carbon should be excluded even if the isolated particles exhibit a homogeneous microstructure. 

By definition, amyloid deposits stained with Congo red dye express green birefringence under polarized light microscopy (3). Electron microscopy... 

Endotherm (3) indicates the melting at 526 K, and finally, there is a broad, exotherm with two peaks (4) due to decomposition. Again, this DTA curve is quite characteristic of poly(ethylene terephthalate) and can be used for its identification. Optical observation to recognize glass and melt by their clear appearances is helpful. Microscopy between crossed polars is even more definitive for the identification of an isotropic liquid or glass (see Sect. 3.4.4). 

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