Light microscopy phase

Figure 3. Light microscopy phase contrast polymer domains chlorobutyl / polypropylene / neoprene blend (CIIR/PP/CR).

Figure 4. Light microscopy phase contrast nylon/EP blends.

Two nucleation processes important to many people (including some surface scientists ) occur in the formation of gallstones in human bile and kidney stones in urine. Cholesterol crystallization in bile causes the formation of gallstones. Cryotransmission microscopy (Chapter VIII) studies of human bile reveal vesicles, micelles, and potential early crystallites indicating that the cholesterol crystallization in bile is not cooperative and the true nucleation time may be much shorter than that found by standard clinical analysis by light microscopy [75]. Kidney stones often form from crystals of calcium oxalates in urine. Inhibitors can prevent nucleation and influence the solid phase and intercrystallite interactions [76, 77]. Citrate, for example, is an important physiological inhibitor to the formation of calcium renal stones. Electrokinetic studies (see Section V-6) have shown the effect of various inhibitors on the surface potential and colloidal stability of micrometer-sized dispersions of calcium oxalate crystals formed in synthetic urine [78, 79]. 

Light microscopy allows, in comparison to other microscopic methods, quick, contact-free and non-destmctive access to the stmctures of materials, their surfaces and to dimensions and details of objects in the lateral size range down to about 0.2 pm. A variety of microscopes with different imaging and illumination systems has been constmcted and is conunercially available in order to satisfy special requirements. These include stereo, darkfield, polarization, phase contrast and fluorescence microscopes. 

Figure 5.19 Vesicle-encapsulated microtubes in bolaamphiphiles with oligoglycine head groups (33) observed using phase contrast light microscopy (a, b) in water at 25°C and (c) after vacuum drying. Reprinted from Ref. 53 with permission of Wiley-VCH.

One of the key experimental results leading to the elucidation of this overall structural puzzle involved depolarized reflected light microscopy (DRLM) studies on NOBOW freely suspended films in the high-temperature SmCP phase.48 In the freely suspended films it appears that only one phase is observed, which is assumed to be the phase forming the majority domains in the EO cells. The DRLM experiment provides two key results. First, thin films of any layer number have a uniformly tilted optic axis, suggesting all of the layer interfaces are synclinic. Second, films of even-layer number are nonpolar, while films of odd-layer number are polar, with the polar axis oriented normal to the plane of the director tilt (lateral polarization). 

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... 

Reflected light Microscopy can be used for examining the texture of solid opaque polymers. Materials which can be prepared as thin films are generally examined by transmitted light. Two common techniques used are (i) polarised-light Microscopy, and (ii) phase contrast Microscopy. 

When supersaturated fresh gallbladder bile (or model bile) is centrifuged to remove solid crystalline and amorphous precipitates, and supernatant vesicles, and the resultant isotropic (one phase) solution maintained in a dust-free environment at 37 °C and examined daily by light microscopy, cholesterol crystals can be observed to precipitate. The time taken for these solid cholesterol... 

Fluorescent light microscopy distinguishes between the extractable liquids, which fluoresce strongly, and the matrix, which does not. The disruption of weak bonding effected by thermal treatment, which increased the extract yield, was paralleled by changes in fluorescence intensity. The fluorescence spectra of the extracts also reflect the compositional differences between the mobile phase and the solubilised coal network. 

The normal cell cycle consists of a definable sequence of evenfs fhaf characferize fhe growfh and division of cells and can be observed by morphological and biochemical means. The cell cycle is depicfed in Fig. 55.1. Two of the four phases of the cell cycle can be studied directly the M-phase, or mitosis, is easily visible using light microscopy because of chromosomal condensation, spindle formation, and cell division. The S-phase is the period of DNA synthesis and is observed by measuring the incorporation of tritiated thymidine into cell nuclei. 

The appearance of tubular myelin-like structures in swollen lecithin was observed by light microscopy well before the systematic investigation of liposomes [351-352]. Similarly, it was also demonstrated some time ago that the addition of calcium ions converted phospholipid liposomes to cochleate cylinders [353]. Subsequent studies have, however, revealed that the system is extremely complex. For example, examination of the phase-transition behavior of synthetic sodium di-n-dodecyl phosphate [(C12H2sO)2PO2Na+ or NaDDP] and calcium di-n-dodecyl phosphate [Ca(DDP)2] showed the presence of many diverse structures [354]. In particular, hydrated NaDDP crystals were shown to form lyotropic liquid-crystalline phases which transformed, upon heating to 50 °C, to myelin-like tubes. Structures of the tubes formed were found... 

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. 

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. 

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