Electron microscopic sections

Recognition of hyperbolic periodic cytomembrane morphologies in electron microscopic sections... 

Somogyi P. Hodgson AJ (1985) Antisera to gamma-aminobutyric acid, 111. Demonstration of GABA in Golgi-impregnated neurons and in conventional electron microscopic sections of cat striate cortex. J Histochem Cytochem 33 249-257. 

The choice of label will depend on the application envisaged. Enzymes are widely applicable they are used in assays, such as ELISAs, and for detection of antigen blotted or dotted on membranes or embedded in tissue sections. Enzyme labels have also be used for the location of antigen in electron microscope sections but gold labelled antibodies (Chapter 11) are now extensively employed for this purpose. Antibodies labelled with a fluorescent molecule are used in assays and for the detection of antigens in tissue sections and also for flow cytometiy and fluorescence-activated cell sorting. 

X-ray fluorescence spectroscopy (XRF) is a technique for the determination of elemental composition of materials, for elements greater than atomic number 11, present above 0.05% concentration [27-29]. The technique is similar to the EPMA, and x-ray analysis in the electron microscope (Section 2.6.1), except that the EPMA is used for local analysis whereas XRF is a bulk technique. Exposure of the sample to an x-ray beam causes electrons to be ejected and outer shell electrons to fall into the vacancies, emitting x-rays of discrete energy. Characteristic energies are associated with specific elements and the x-ray intensities are related to the concentration of the element in the sample. There are problems with this direct association of x-ray intensity and concentration, due to absorption by the matrix but standards and software programs are available to calculate elemental composition. XRF experiments have the advantage of being rapid and nondestructive. These techniques are usefully applied to the assessment of fillers, additives and contaminants in polymers, and software is available for quantitation. 

Most tests of the validity of the BET area have been carried out with finely divided solids, where independent evaluation of the surface area can be made from optical microscopic or, more often, electron microscopic observations of particle size, provided the size distribution is fairly narrow. As already explained (Section 1.10) the specific surface obtained in this way is related to the mean projected diameter through the equation... 

The polyethylene crystals shown in Fig. 4.11 exist as hollow pyramids made up of planar sections. Since the solvent must be evaporated away prior to electron microscopic observation, the pyramids become buckled, torn, and/ or pleated during the course of sample preparation. While the pyramidal morphology is clearly evident in Fig. 4.1 la, there is also evidence of collapse and pleating. Likewise, the ridges on the apparently planar crystals in Fig. 4.1 lb are pleats of excess material that bunches up when the pyramids collapse. 

Fig. 2. A series of progressively closer (scanning electron microscope) SEM photographs of the same membrane cross section, clearly showing skin and...

Measurement of Cross Section with a Scanning Electron Microscope... 

To illustrate the effect of radial release interactions on the structure/ property relationships in shock-loaded materials, experiments were conducted on copper shock loaded using several shock-recovery designs that yielded differences in es but all having been subjected to a 10 GPa, 1 fis pulse duration, shock process [13]. Compression specimens were sectioned from these soft recovery samples to measure the reload yield behavior, and examined in the transmission electron microscope (TEM) to study the substructure evolution. The substructure and yield strength of the bulk shock-loaded copper samples were found to depend on the amount of e, in the shock-recovered sample at a constant peak pressure and pulse duration. In Fig. 6.8 the quasi-static reload yield strength of the 10 GPa shock-loaded copper is observed to increase with increasing residual sample strain. 

Run-of-the-mill instruments can achieve a resolution of 5-10 nm, while the best reach 1 nm. The remarkable depth of focus derives from the fact that a very small numerical aperture is used, and yet this feature does not spoil the resolution, which is not limited by dilfraction as it is in an optical microscope but rather by various forms of aberration. Scanning electron microscopes can undertake compositional analysis (but with much less accuracy than the instruments treated in the next section) and there is also a way of arranging image formation that allows atomic-number contrast, so that elements of different atomic number show up in various degrees of brightness on the image of a polished surface. 

Microscope Study of the Surfaces of Sectioned M-17 Propellant Grains , PATR 2177 (1955) 23) S.M. Kaye, An Electron Microscope Study of the Surfaces of Sectioned M-15 Propeiiant Grains , PATR 2201 (1955) 24)S.M. Kaye,... 

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