Subject internal transmission

Fig. 13.9 Transmission electron microscopic data ofendocytosis. Saos-2 cell was treated with LDH and after 1 h the cell was fixed and subjected to TEM measurement. (A) successive internalization of LDH via endocytosis access of LDH around plasma membrane, formation of membrane ruffles and interaction...

SEM is particularly useful for showing up the surface structure of materials by analysing the secondary electrons. Transmission electron microscopy (TEM) relies on the use of the electrons passing through the very thin samples and can show up images of the internal structure of samples. It can achieve a resolution of about 1 x 10-10 m. Both SEM and TEM require a high vacuum and so samples must be stable in vacuums and when subjected to fast moving electrons. 

Hence, in contrast to transmission spectroscopy, where the sample intercepts the path of the IR beam, in ATR the sample is placed on an IR-transparent crystal (IRE, internal reflection element), permitting total internal reflection. In vivo (or in situ) experimentation is permitted by virtue of one of several design arrangements (a) the region of skin under study may be placed directly in contact with the crystal (b) a remote fiber-optic probe (with IRE head) may be used to transfer the IR beam from the source to the sample and ultimately to the detector and (c) samples removed from the subject may be placed directly onto the crystal. 

The surface morphology of grains has been studied by secondary electron microscopy (SEM) (Hoppe et al., 1995). Such studies have been especially useful for pristine SiC grains that have not been subjected to any chemical treatment (Bernatowicz et al., 2003). Finally, the transmission electron microscope (TEM) played an important role in the discovery of presolar SiC (Bernatowicz et al., 1987) and internal TiC and other subgrains in graphite (Bernatowicz et al., 1991). It has also been successfully applied to the study of diamonds (Daulton et al., 1996) and of polytypes of SiC (Daulton et al., 2002, 2003). 

Hermann et al. (1969) have reviewed the subject of infrared spectroscopy at subambient temperatures, including an extensive literature review with over 6(X) references and discussions of work on pure molecules, and on molecules and molecular fragments within matrices. Hermann and coworkers (Hermann and Harvey, 1969 Hermann et al., 1969 Hermann, 1969) have also discussed the design of cells for use at low temperatures. These cells belong in four categories conventional transmission cells matrix isolation cells pseudomatrix isolation cells and multiple internal reflection cells (ATR). 

For information on modeling of VLSI interconnects and their transmission line treatment, consult the Proceedings of Design Automation Conference and International Conference on Computer-Aided Design. IEEE Transactions on CAD is also an excellent source of information on the subject. 

Electron microscopy and diffraction are indicated whenever one dimension of the particle is 2000 A or less, or when fine surface or internal structure is in question. It is therefore preeminent for thin films or crystals and for very fine-particle characterization where other methods fail or are of limited utility. Bulk materials can also be examined by thinning down to foils. The chief limitation is that the electron beam can, in general, give information on materials only less than about 2000 A in thickness by transmission. Where samples are not thinned, information on surface structure can be gained by replica techniques and by reflection diffraction. Several books have appeared on the subject and these provide details on the various applications and capabilities of the technique. ... 

---