Differential interference contrast optics

Fig. 15. Aortic lesion stained to visualize lipid deposits and viewed with Nomarski differential interference-contrast optics (Sudan IV)...

The first method takes advantage of the cortical location of mitoses 11-13. Edgar et al. (1994) first identified live embryos that were undergoing mitosis by the disappearance of the nuclear envelope under DIG (differential interference contrast) optics. The embryos were then aged for appropriate time intervals to reach desired points in the following division cycle, prior to homogenization. Half of the extract from one embryo was used for HI kinase assays and the other half was immunoblotted to correlate kinase activity with phosphorylation on Cdkl and with cyclin levels. 

In video microscopy, for instance, background is normally subtracted using differential interference contrast (DIC) [18]. This technique, which requires a number of manipulations from the user, may now be automated using a new method called polarization-modulated (PMDIC) [19,20], It requires the introduction of a liquid crystal electro-optic modulator and of a software module to handle difference images. PMDIC has been shown to bring improvements in imaging moving cells, which show a low contrast, as well as thick tissue samples. 

Optical microscopy, such as phase contrast or differential interference contrast. 

Powerful methods that have been developed more recently, and are currently used to observe surface micro topographs of crystal faces, include scanning tunnel microscopy (STM), atomic force microscopy (AFM), and phase shifting microscopy (PSM). Both STM and AFM use microscopes that (i) are able to detect and measure the differences in levels of nanometer order (ii) can increase two-dimensional magnification, and (iii) will increase the detection of the horizontal limit beyond that achievable with phase contrast or differential interference contrast microscopy. The presence of two-dimensional nuclei on terraced surfaces between steps, which were not observable under optical microscopes, has been successfully detected by these methods [8], [9]. In situ observation of the movement of steps of nanometer order in height is also made possible by these techniques. However, it is possible to observe step movement in situ, and to measure the surface driving force using optical microscopy. The latter measurement is not possible by STM and AFM. 

Fig. IS. (a) Schematic illustration of optical writing process based on hydrogen evolution in a-Si H. (b) Optical differential interference contrast micrograph of bubbles in a 0.5-/un-thick film written with a laser pulse of 3 ftsec and 28 mW power measured before the optics, (c) SEM micrograph of microbubbles.

Hie most important optical technique for examining semiconductor wafer surfaces is the differential interference contrast microscopy method of Nomarski (N-DIC). First described in 1952, DIG... 

A Nikon optical microscope was used to observe states of flocculation of large emulsion droplets. The emulsion samples were regularly viewed with the microscope using the Normarski differential interference contrast technique.16 Creaming behaviour was examined by visually measuring the height (thickness) of cream and serum layers in emulsions stored at 22°C at regular time intervals. 

To understand the release mechanism, cryomicrotomy was used to slice 10 m-thick sections throughout the matrices. Viewed under an optical microscope, polymer films cast without proteins appeared as nonporous sheets. Matrices cast with proteins and sectioned prior to release displayed areas of either polymer or protein. Matrices initially cast with proteins and released to exhaustion (e.g., greater than 5 months) appeared as porous films. Pores with diameters as large as 100 /xm, the size of the protein particles, were observed. The structures visualized were also confirmed by Nomarski (differential interference contrast microscopy). It appeared that although pure polymer films were impermeable to macromolecules (2), molecules incorporated in the matrix dissolved once water penetrated the matrix and were then able to diffuse to the surface through pores created as the particles of molecules dissolved. Scanning electron microscopy showed that the pores were interconnected (7). 

Finally, colloidal particles may be observed directly by high-performance microscope systems (an ultramicroscope or optical microscope with differential interference contrast) (Saucier, 1993, 1997). 

Then, microscopic examinations follow optical research microscopes allow to determine the number, thickness, and color sequence of layers in paint fragments, and to recognize the textures as well as fundamental features of pigment and extender mixtures. Bright field and dark field illuminations, polarized light microscopy (incident and transmitted), particularly the differential interference contrast (DIC) procedure, and fluorescence microscopy are necessary for paint examinations (see Figure 3(A)-3(E)). 

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