Image, dark-held

Figure 2.3. A schematic diagram of bright-held (bf) TEM imaging. A dark-held (df) image is formed using a diffracted electron beam.

Thus, one-dimensional parallel and rotational moire fringes can be clearly distinguished because they are always normal and parallel to g, respectively. Whether a one-dimensional or two-dimensional moire pattern is produced depends on the number of doubly diffracted beams that pass through the objective aperture. It is clear from Figure 6.5 that moire fringes will also be produced in dark-held images. 

Figure 3.17 Arrangement for (a) bright-held image and (b, c) dark-held image, (a) (h)...

Fig. S (a) and (b) TEM images of cone-shaped ZnO nanocrystal. Inset in (b) shows a dark held image of a single cone-shaped nanocrystal. Reproduced...

The high sensitivity of the dark-held anisotropic observation method suggests its possible application for magnetic nanoparticles imaging that we discuss in brief in Sechon 10. 

Different techniques can be used to enhance the contrast. For example, dark-held images can be produced by blocking the transmitted electrons and using only the scattered electrons. 

When the lenses are defocused, so that a small crossover is formed before or after the specimen, the central spot of the CBED pattern will become a bright-held shadow image of the specimen and each diffraction spot will become a dark- held shadow image showing the variation of intensity within the illuminated zone, this is the afore mentioned a) variant. 

Although many studies on DNA and DNA-protein interaction have utilized metal shadowing to produce bright-held image contrast, dark-held TEM (annular or spectroscopic) of unstained or uranyl acetate-stained and metal-shadowed nucleic acid-protein complexes also provides useful resolution. In Figure 5, a short length of DNA (2356 base pairs), with attached progesterone receptor, is revealed by dark-held TEM. The RecA protein has the ability to... 

Donald and Windle" have used the technique of dark-held diffraction imaging to provide information relating to the spatial distribution of selected orientations. Thus by imaging an area using only part of an arced diffraction spot, the image highlights those domains with that particular orientation. 

Figure 14a is a typical TEM micrograph of Pt/C shadowed standard-size PTFE dispersion particles, (here sample G) with dark-field images of unshadowed particles in the insets typical BFDC micrographs of several standard-size DuPont dispersion particles are shown in Fig. 14b and c. The dark-field micrographs, taken with 100 reflections, are similar to the bright-held ones except... 

GSD microscopy has been shown to image immunolabeled protein clusters on the plasma membrane of hxed cells with Ar = 50-90 nm resolution using a CW laser power of a few kilowatt per square centimeter [105]. However, plain GSD microscopy is currently challenged by the fact that the repeated population of the triplet state or similar dark states augments photobleaching [105]. Nonetheless, this early concept was important for the development of far-held optical nanoscopy for a number of reasons. First, it highlighted... 

Figure 3.34 Images of polycrystalline specimen of thallium chloride (a) SAD ring pattern and (b) bright-held image in which the dark circle (50 //m diameter) indicates the area selected for diffraction. (Reproduced with permission from M. von Heimandahl, Electron Microscopy of Materials, Academic Press, New York. 1980 Elsevier B. V.)...

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