Micrographs, dark field

Figure 4.11 Electron micrographs of polyethylene crystals, (a) Dark-field illumination shows crystals to have a hollow pyramid structure. (Reprinted with permission from P. H. Geil, Polymer Single Crystals, Interscience, New York, 1963.) (b) Transmission micrograph in which contrast is enhanced by shadow casting [Reprinted with permission from D. H. Reneker and P. H. Geil, /. Appl. Phys. 31 1916 (I960).]...

Figures 4.1 la and b, respectively, are examples of dark-field and direct transmission electron micrographs of polyethylene crystals. The ability of dark-field imaging to distinguish between features of the object which differ in orientation is apparent in Fig. 4.11a. The effect of shadowing is evident in Fig. 4.11b, where those edges of the crystal which cast the shadows display sharper contrast.

Fig. 10. A dark field (DF) transmission electron micrograph showing interface in a continuous fiber (F) a-Al202 (F)/Mg alloy (ZE41A) matrix (M) within...

Fig. 7. Dark-field micrographs from Ref. for the Ni-0.247 A1 alloy after the two-step quench, first to T = 903 K, and then to T = 343 K (which supposedly corresponds to areas b and d, respectively, in Fig. 1), at following times t after the second quench (in minutes) (a) 0, (b) 10, (c) 100, (d) 1000, and (e) 10000.

Figure 48-6. Dark field electron micrograph of a proteoglycan aggregate in which the proteoglycan subunits and filamentous backbone are particularly well extended. (Reproduced, with permission, from Rosenberg L, Heilman W, Kleinschmidt AK Electron microscopic studies of proteoglycan aggregates from bovine articular cartilage. J Biol Chem 1975 250 1877.)...

An examination of a dark-field micrograph of a field such as that of Fig. 1 confirms the presence of an appreciable proportion of multiply twinned particles, and also shows that most of the particles are orientated with a 111 parallel to the substrate (29, 30). 

Figure 12. A dark-field transmission electron micrograph of a (lll)Ag platelet grown on single-crystal MoS2. The regions with different contrast differ in thickness by one monatomic step from one another. The larger the number marked on each region, the thicker the crystal (3, 71).

Figure 5.15 Dark-field optical micrograph of self-assembled helical filaments from an aqueous dispersion of 2Ci2-L-GluCnN+ (22) after aging for 30 h. Bar = 10 xm. Reprinted with permission from Ref. 74. Copyright 1985 by the American Chemical Society.

Figure 5.41 (a) Dark-field light micrograph of double-helical ropes formed from homoditopic... 

Figure 7.5 Transmission electron micrographs of a Pd/AFC), catalyst in bright (above) and dark field (below). The latter shows enhanced contrast for the Pd particles as well as better resolution (from Freeman et al. [14]).

Figure 45. Dark-field micrograph of a small segment of unstained, unshadowed, naked double-stranded DNA from a bacteriophage. A relatively well-preserved image of the two-dimensional projection of the double helix is seen in the left half. The scale bar equals 35 A (116). (Reproduced with kind permission from the Annual Review of Biophysics and Bioengineering, Vol. 8 1979 by Annual Reviews, Inc.)...

Dark field micrographs obtained from in situ hybridization experiments, demonstrating the colocalization of hupS and nifH mRNAs in pea nodules containing R. leguminosarum bv. viciae... 

Figure 8. Micrograph of area from which Figure 7 was obtained dark field X 12,000...

The contrast observed on the micrographs results essentially from the variations in intensity of the electron beam diffracted by the 002 interferences as a function of the direction of the C-axis, both in bright field where the diffracted rays are stopped by the contrast diaphragm and in dark field where the image is formed by these rays alone. This result has been demonstrated theoretically, at least, in the case of elastic diffusion. It is found that the energy scattered in a given direction by a pregraphitic structure depends on the orientation of the lattice in relation to the incident beam (17). 

Figure 4-16 (A) Dark field electron micrograph of a proteoglycan aggregate from bovine articular cartilage (from bearing surfaces of joints). Courtesy of Joseph A. Buckwalter. The filamentous backbone consists of hyaluronic acid, as in (B). The proteoglycan subunits extend from the backbone. From Rosenberg.149...

Figure 5-13 Electron micrograph of a DNA molecule (from a bacterial virus bacteriophage T7) undergoing replication. The viral DNA is a long ( 14 pm) duplex rod containing about 40,000 base pairs. In this view of a replicating molecule an internal "eye" in which DNA has been duplicated is present. The DNA synthesis was initiated at a special site (origin) about 17% of the total length from one end of the duplex. The DNA was stained with uranyl acetate and viewed by dark field electron microscopy. Micrograph courtesy J. Wolfson and D. Dressier.

Fig. 2. In situ localisation of rabl6 mRNA in developing wheat seeds. A, Scanning electron micrograph of scutellar/starchy endosperm boundary. DC, depleted cells SE, scutellar epithelial cells. B, Dark field micrograph of in situ hybridised rabl6 sense RNA probe. No specific hybridisation is visible. C, Dark field micrograph of in situ hybridised rabl6 antisense RNA probe. Note specific hybridisation to depleted cells. Scanning electron microscopy was performed according to Mundy et al. (1986) in situ hybridisation after Raikhel et al. (1989).

This process (using one of the modes previously described) was applied to a set of 3 to 12 different selected areas on the transverse section of one fiber. The photographic series is a completed record of the whole fiber cross-section at an adequate magnification. On the latter micrograph the irradiated areas can be seen because of their lesser electron density in bright field conditions. In some cases, these irradiated areas could also be seen under dark field conditions. 

Figures 11 to 13 are dark field micrographs of 66 polyamide monofilaments. Figure 11 show an Ag-S stained filament. Silver sulfide precipitates, which appear as black areas (as they did in bright field images) as well as polyamide crystallites (bright spots) are visible. Figure 12 corresponds to a type 4 fiber (with skin-core morphology) where there is a lower density of crystallites in the skin region. Figure 13 corresponds to the case of type 5 fiber which has smaller crystallites.

Figure 11. Dark field micrograph of 66 polyamide microfilaments...

Figure 12. Dark-field micrograph of the cross section of an Ag,S-stained Type 2 (see text) PA 66 fiber. Notice black deposits of silver sulfide in the periphery and white dots in the whole section, corresponding to crystallites in Bragg position.

Figure 13. Dark-field micrograph of me cross section of a Type 4 PA 66 fiber. No silver sulfide deposits notice the skin-core effect and the dimensions of the...

Figure 4. Microautoradiographs of freezing microtome cross sections through a spring whejj embryo and the primary leaf tip after seed dressing with [ C]Baytan (dark-field micrograph).

Figure 7. Radioactivity in barley leaf tissue j ter treating the upper side of the lower half of the leaf with [ C]triadimefon (microautoradiograph, dark-field micrograph). (Reproduced with permission from Ref. 19. Copyright 1978 Pflanzenschutz-Nachrichten Bayer.)...

FIGURE 7.10. Dark-field optical micrographs of aqueous dispersions of 2C12-L-Glu-C11N+ (65b, n = 12) (10-3 M). Aging condition (a) 20 °C, several hours (b) 15-20 °C, 1 day (c) 5-6 hours after (b) (d) after 1 month at 15-20 °C. Bars, 10pm. Reproduced with permission of the American Chemical Society. 

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... 

Figure 3. (a) Annular-dark-field electron micrograph of [Fe (2 nm)/ oxide]x50 showing path of EELS probe (b) O/Fe ratio along line scan for model profile (solid curve), convolved profile (dotted curve) and experimental points (filled circles) [8]. 

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