Replication microscopy

Surface cracks in boiler tubes, creep damage in power plant components and precipitate analysis in components subjected to high temperature and stress have been successfully assessed by this technique and necessary further inspection scheduled, depending upon the severity of the observed defect. The following is an example of the type and severity of defects and the necessary action taken in the context of power plant operations. 

Microscopic creep cracks Inspection after lOOOOh 

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General corrosion control, prevention, and monitoring should be planned for from the onset. To detect and monitor corrosion, various methods must be used, while corrosion protection would be done by the addition of inhibition and use of protection coatings [5]. Visual examination, laser methods, the replication microscopy liquid penetration testing method, magnetic particles testing, the eddy current inspection method, acoustic emission technique, thermal methods of inspection, and nondestructive methods are the various methods to be adopted when monitoring pipeline corrosion [5]. 

Scanning electron microscopy and replication techniques provide information concerning the outer surfaces of the sample only. Accurate electron microprobe analyses require smooth surfaces. To use these techniques profitably, it is therefore necessary to incorporate these requirements into the experimental design, since the interfaces of interest are often below the external particle boundary. To investigate the zones of interest, two general approaches to sample preparation have been used. 

The processes of meiosis and mitosis involve many motile events, from the separation of the daughter chromosomes to the final act of cell separation at cytokinesis (Wadsworth, 1993). DNA replication itself may be considered as a motile event, because the polymerase complex moves along the linear DNA. One of the most obvious motile events is the separation of the chromosomes along the mitotic spindle at anaphase. Details of the structure and polarity of microtubules in the spindle apparatus in meiosis and mitosis are known through electron and light microscopy, but it is not yet clear whether the chromosomes are pushed, pulled or... 

Electron Microscopy can be used for resolution of smaller objects the practical limit of resolution being a few angstrom units. Electron Microscopy has been used in the study of the morphology of crystalline polymers. The usual techniques of replication, heavy-metal shadowing, and solvent etching are widely used. The direct observation of thin specimens, like polymer single crystals, is also possible and permits the observation of the electron-diffraction pattern of some specimen area, which is invaluable for... 

Figure 4.26 (a) DNA replication at low resolution (for example as seen by electron microscopy). Only one replication fork is visible and it appears that both strands of the parental DNA replicate continuously in the same direction, which cannot be the case, since the two strands of parental DNA are anti-parallel, (b) The problem is solved by the priming of DNA synthesis with short RNA primers, whose 3 -hydroxyl can be used by DNA polymerase, producing Okazaki fragments, while on the other strand, DNA synthesis is continuous. (From Voet and Voet, 2004. Reproduced with permission from John Wiley Sons., Inc.)... 

Electron Microscopy of Cellulose Acetate Reverse-Osmotic Membranes by Means of the Improved Replication Method... 

These results were confirmed by an electron microscopy study using a freeze-etching replication technique (1 ). The aim of this technique was to conserve the real gel structure by blocking any diffusion processes in the gel sample by the freezing action of liquid nitrogen. The three-dimensional network is then recovered... 

Triplicate aliquots were taken for particle size analysis and two of those aliquots were mixed for BET surface area analysis results are in Table III. The nine samples were individually sieved for size distribution. A chi-squared test was performed on each triplicate set in order to check the apparent efficiency of composite mixing. For all three composite samples, there was a 90 percent probability that each of the three replicates from each composite sample came from the same population. The A and C samples were combined and evaluated for surface area by nitrogen adsorption (BET). The B samples were then subjected to scanning electron microscopy (SEM) analysis. 

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.

Electron photomicrographs and surface replicate photographs were skillfully obtained by M. E. Testa of our microscopy department. His assistance and interpretations are gratefully acknowledged, as well as the permission of The Goodyear Tire Rubber Co. to publish these findings. 

Fig. 20 (a) Stacked layers of parallel helices, with a 120° twist between adjacent layers, result in a sieve-like pattern with hexagonal symmetry, (b) A similar structure is obtained by inter-connected DNA strands and replicated into millimeter-sized crystals, as shown in the optical microscopy image in (c). Adapted with permission from [81]. (d) Design of a triangle from seven strands. The relative position of helices (1, 2, 3) at the vertices (a, b, c) is discussed in the text. Sticky ends mediate the aggregation of tiles into macroscopic rhombohedral crystals, shown in the optical microscopy image in (e). Adapted with permission from [82]... 

Transmission Electron Microscopy (TEM) micrographs were obtained using a BS 540 (Tesla) apparatus. Microscope samples were prepared using the platinum-carbon replication method, with evaporation of platinum and a low amount of carbon onto the adsorbents, then treated in HF to dissolve silica gel. 

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