Epoxy resin-embedded sections

Figure 2 shows STEM images of a 8%wt Pd/2%wt Pt catalyst which is supported on charcoal. The sample was prepared for microscopy by embedding in epoxy resin and sectioning with a diamond knife in an ultramicrotome, and was examined in a Vacuum Generator s Ltd HB5 STEM, with a 5A probe. The sample thickness is about 500A. 

If epoxy resin-embedded tissue is used, cut 2- jm-thick sections with a glass knife, mount on APES-coated slides, and dry as described in Note 2. Deplasticize the sections by immersing them in sodium eth(meth)oxide for 15 min (8). Wash the sections twice with equal parts of methanol (or IMS) and xylene, twice with methanol, for 3 min each, and rehydrate. Afterward, the same HIER and immuno-histochemical protocols are employed as in paraffin sections. 

Epoxy resin-embedded semithin sections of 1-2 j,m may also be used following extraction of the resin with a sodium meth(et)hoxide treatment for 5-8 min. Sodium meth(et)hoxide is prepared by saturating methanol or ethanol with sodium hydroxide pellets. 

There are two different ways to perform electron microscopic immunocytochemistry pre-embedding and postembedding (Stirling, 1990). Pre-embedding electron microscopic immunocytochemistry applies the antibodies and label to samples just after fixation but before embedding in epoxy resin and sectioning. Postembedding electron microscopic immunocytochemistry applies antibodies and label to thin sections made after the samples have been embedded in epoxy resin and sectioned. 

Postembedding electron microscopic immunocytochemistry - a method that uses antibodies applied to sections after embedding in epoxy resin and sectioning with an ultramicrotome. 

As a representative application example, the analysis of a paint chip of an automobile by using an FT-IR microspectroscopic system equipped with a 64 x 64 two-dimensional MCT array detector is described. A paint chip embedded in an epoxy resin was sectioned using... 

Ceynowa performed a TEM study of microtomed Nafion 124 membranes. To increase the electron density contrast, H+ form membranes were converted to the Pb + form using 1.0 M Pb(N03)2 for 60 h. Then, the sample was dehydrated using ethanol solutions, rehydrated in 1,2-epoxypropane, and embedded into epoxy resin. Ultrathin sections were cut to 60-80 nm size. TEM images of the film indicate ion cluster of 3-6 nm in diameter uniformly distributed in the polymer matrix. ... 

Figure 9.1 Cross-sections of a typical inert or redox electrode, embedded (a) within glass, and (b) within epoxy resin. Type (b) is preferred if the metal is liable to melt or react when very hot.

Figure 13.3.7 shows scanning electron microscopy (SEM) photographs of the surface of the polyethylene particle after the silica particles were peeled off. The specimen was prepared in the following way. After the composite particles were potted in epoxy resin, the dried resin block was cut using a microtome to produce fine sections. The fracture surface appearance of the polyethylene was then observed under a microscope. The mean depth penetration into the surface of the core particles could be measured using the SEM photographs. Silica 0.3 pan in diameter was embedded in the surface of the polyethylene particles at a depth of 0.03 xm. In... 

Heating is effective in antigen retrieval on semithin and thin sections of resin-embedded tissues. This results not only from the breakdown of protein crosslinks introduced by aldehyde but also from the breakage of bonds between the epoxy resin and the embedded tissue (see Fig. 7.2). It is known that epoxy resins form covalent bonds with tissue proteins during embedding. 

In TEM, thin sections of samples are embedded in epoxy resins or, alternatively, platinum-carbon replicas of the samples are produced in order to the avoid release of vapor or gases. 

After the last experiments, the rats are euthanized by injection of an overdose of pentobarbital and then perfused intracardially with a phosphate-buffered 2.0% paraformadehyde - 2.5% glutaraldehyde fixative. Methyl green solution was injected to confirm the location of the catheter after the perfusion. The spinal cord and nerve roots were dissected out and immersed in the same fixative for 4 h. Two specimens (10 mm rostral and caudal to the conus medullaris from each rat were postfixed with cacodylate-buffered 1 % osmium tetroxide dehydrated in a series of graded alcohol solutions, and embedded in epoxy resin. From the embedded tissue, 1-pm transverse sections were obtained and stained with toluidine blue dyes. Sections obtained from 10 mm rostral to the conus (caudal spinal cord) were used for qualitative evaluation. Quantitative analysis of nerve injury was performed using the sections obtained form 10 mm caudal to the conus. Each fascicle present in the cross section was assigned to an injury score 0 to 3. The injury score for each cross section was then calculated as the average score of all fascicles present in the cross section. 

The brominated sticks are embedded in Spurr epoxy resin (Spurr 1969) and sectioned with a diamond knife or glass knife mounted on an ultramicrotome to give cross sections of 0.15//m thickness for TEM-EDXA or 0.5//m thickness for SEM-EDXA. The sections are then placed on a carbon-coated collodion film on the specimen support grid. The specimens are carbon-coated again to avoid charging. 

Fig. 3 shows SFM image of one of the sections (thickness of - 100 nm) of K562 cell embedded in epoxy resin. It should be noticed that topographical contrast and the identification of the K562 internal ultrastructure critically depend on the procedure of cell preparation before embedding (chemical fixation or high-pressure freezing and freeze-substitution). 

To circumvent the limitations described above, Plummer et al. have used a different method, suitable for observation of plastic zones in bulk samples [30]. They embedded a DCB sample in a low viscosity epoxy resin with the razor blade in place. The crack tip was therefore maintained under stress while the resin was left to cure at room temperature. The sample was then trimmed for thin sectioning, stained by immersion in a Ru04 solution, and microtomed in thin sections in the region of the plastic zone for observation by TEM. While this method gave particularly good results on ductile semicrystalline systems where a deformed thin film would not have been representative of the plastic deformation mechanisms taking place in bulk samples, it should in principle be applicable fairly generally. 

TEM (Transmission Electron Microscopy) analysis. This analysis was done on a Philips 420T microscope (120kV, maximum resolution 5A) equipped with an EDAX PV9900 EDS. The catalysts were ground to a powder, embedded in epoxy resin and then microtomed with a diamond l fe to obtain sections about 300A thick. Images were taken at 100 kV. Diameters of about 100 isometric-shaped Pt crystallites were measured for each sample. 

Inhomogeneities [137] and traveling waves of the initiator [138] have been investigated during the formation of PMMA, and the spatial variation and the dynamics of a photo-induced polymerization have been followed in another example [139]. The curing of adhesives [112], and the influence of embedded fibers on the loeal polymerization rates of epoxy resins [140, 141], have been investigated in a similar way. A related subjeet is the vulcanization process of elastomers (cf. Section 5.2.2). 

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