Crystals polarized light microscopy

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. 

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. 

There are several techniques used to image the microstructure of fat crystal networks. (See Chapter 11 on Imaging. ) The most commonly used imaging method is polarized light microscopy (PLM) since fat crystals are birefringent and appear white, while the liquid oil is not and thus appears black. 

ZOpT can be used to study both self-similar and self-affine fractal objects. The data at low frequencies (u and v <10) is not to be included in the calculation of D j. Figure 17.25 from Tang and Marangoni (2006) illustrates how Df, and ZOpT are calculated from the double logarithmic plot ofX vs. Y for polarized light microscopy images of the fat crystal networks. 

To obtain the fractal dimension of a network of particles, acquiring images of the microstructure is necessary. Many forms of microscopy can be used, including brightfield microscopy, confocal laser scanning microscopy, scanning electron microscopy, and in the case of fat crystal networks, polarized light microscopy. 

The characterization of liquid crystals by polarized light microscopy is the most straightforward method available and, whenever possible, it should be carried out in the initial stages of an investigation on new polymers. Thermal analyses alone can be misleading. In this procedure, a thin layer of the melt is kept at constant temperature on a hot-sta and obsawed between crossed polars. The appearance or texture of the melt is dependent on the structure of the mesophase, and, therefore, it is often possible to directly identify the type of mesophase present by this method. A good review of the microscopy of liquid crj b ajqjears in the books by Hartshome and by Demus and Richter... 

As briefly mentioned earlier, thermal studies have been used in conjunction with characterization by polarized light microscopy to determine the miscibility of polymeric and small molecule liquid crystals and low molecular weight mesogens, of the same or different types of liquid crystallinity, can also be used as plasticizers or diluents for polymers, as demonstrated in a study involving side chain liquid crystalline polymers... 

Fig. 4. Fractional crystallization of anhydrous milk-fat (AMF) (A), MF-TAC (B), and milk-fat MF-TAC with 0.1% milk-fat diacylglycerol (MF-DAC) (Q determined by pNMR measurements of solid fat content, turbidity measurements, and polarized light microscopy coupled to image analysis at 22.5°C. Symbols in (A) and (B) represent the average and standard errors of three replicates. See Figures 2 and 3 for other abbreviations.

Because the crystallization of polymers from their melts is related to their mi-crostructural properties, such as chain conformations and entanglements [83], the polarized light microscopy results suggests a molecular-level difference between the coalesced and as-received PETs even in their melts. 

It has been observed by polarized light microscopy that some emulsion droplets (diameter about 5 /an), containing a triglyceride oil that can partly crystallize at room temperature, have crystalline fat in their outer layer. This has been ascribed to the cooling of the droplets occurring from the outside, so that crystallization would start there. Is this a reasonable explanation ... 

The formation of surfactant crystals (i.e. liquid crystals) at the oil-aqueous interface can be easily determined by the use of polarized light microscopy (35). 

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