Microtome method

We also note data from atomic force microscopy (AFM) versus depth, carried out by using a diamond tip for scratching patterns into the surface [12], Because of the 2° microtoming method reported, these authors were able to examine the depth profile of brittle behavior in weathered samples with excellent resolution. The data showed a very rapid decrease in the brittleness with depth into the sample which, of course, was a strong function of exposure time. The brittleness was more in line with the IR data (see above) versus depth than the molecular weight data, hence suggesting that some chain scission and branching can be tolerated in the system before it manifests brittle behavior. 

Adsorption can be measured by direct or indirect methods. Direct methods include surface microtome method [46], foam generation method [47] and radio-labelled surfactant adsorption method [48]. These direct methods have several disadvantages. Hence, the amount of surfactant adsorbed per unit area of interface (T) at surface saturation is mostly determined by indirect methods namely surface and interfacial tension measurements along with the application of Gibbs adsorption equations (see Section 2.2.3 and Figure 2.1). Surfactant structure, presence of electrolyte, nature of non-polar liquid and temperature significantly affect the T value. The T values and the area occupied per surfactant molecule at water-air and water-hydrocarbon interfaces for several anionic, cationic, non-ionic and amphoteric surfactants can be found in Chapter 2 of [2]. 

Microtome Method A means of determining the surface concentration of species by cutting away a thin surface layer with a knife (microtome), physically separating the layer and analyzing it. 

BS 2782, Part 8, Method 823B, Assessment of pigment dispersion in polyolefin pipes and fittings, microtome method, 1978. 

In earlier research the alignment operation was applied to CNTs in the form of a CNT-polymer resin [24] or CNT suspended in a solvent [25]. In the method developed by Ajayan et al. [24], purified MWCNTs were dispersed in an epoxy resin which was cut with a diamond knife and a microtome in order to obtain aligned CNTs. De Heer et al. [25] used a 0.2 (im pore ceramic filter in order to create an MWCNT suspension in ethanol, and to obtain a black deposit which was transferred to a plastic surface (Delrin or Teflon) by pressing the filter onto the polymer. However, only a moderate degree of orientation and uniformity in length of the CNTs was achieved by this method. 

The goal of our investigations was to characterise the morphology of the sample, and to determine the size and location of the PTFE and silicone oil phases by different methods [46,47], For phase characterization using Raman microscopy, no special sample preparation was necessary. For FTIR imaging, microtomed sections (5 pm in thickness) had to be prepared by cutting the sample with a diamond knife at — 80°C ("cryo-microtomy") to prevent smearing and to obtain flat surfaces. 

For illustrative purposes, the method used by Morgan4 is described below. In this example, cells are re-suspended in agarose gel that is taken up in a 1 mL syringe (see Fig. 6.4), generating a cylinder of cells. The cylinder of cells can be treated like tissue and placed in wax which, in turn, can be cut and embedded in paraffin wax blocks for cutting on a microtome. 

When a colour layer of an artwork is analysed, a drop (5 10 pi) of this solution is localised on the sample surface. This method of enzymatic digestion can be, in principle, applied to all types of samples that occur in restoration practice fragments, cross-sections, microtome slices, etc. The samples are digested in closed microtubes to prevent evaporation of the solution. In the case of the cross-sections and microtome slices, it is essential to ensure the wetness of sample surface for the whole time of digestion. 

To obtain tissue preparations whose constituents were maintained as closely as possible to their state in vivo, the material had to be fixed, i.e. the enzymes inactivated so that cell structures were instantaneously preserved, an almost unattainable ideal. Formalin was the favored fixative, but others (e.g. picric acid), were also employed. Different methods of fixation caused sections to have different appearances. Further artifacts were introduced because of the need to dehydrate the preparations so that they could be stained by dyes, many of which were lipid-soluble organic molecules. Paraffin wax was used to impregnate the fixed, dehydrated material. The block of tissue was then sectioned, originally by hand with a cut-throat razor, and later by a mechanical microtome. The sections were stained and mounted in balsam for examination. Hematoxylin (basophilic) and eosin (acidophilic) (H and E staining) were the commonest stains, giving blue nuclei and pink cytoplasm. Eosinophils in the blood were recognized in this way. 

The method outlined here uses a modification of the Hedley technique (9,10) to prepare nuclear suspensions from the paraffin-embedded tissue samples. Microtome sections are dewaxed, hydrated, and incubated in pepsin with inter-... 

Fig. 3. Bpoxy heterogeneities as a function of amine curing agent content determined by two different methods. The upper series were microtomed samples stained with osmium tetroxide and the lower series were plasma treated fracture surfaces. Both methods gave size and distribution values for the heterogeneities which agreed qualitatively...

Transmission electron micrography has, remarkably, been successfully used to image micelles formed by block copolymers in dilute solutions. Price and coworkers used two preparation methods. In the first method (Price and Woods 1973), f reeze etching, a drop of solution was rapidly frozen by quenching in liquid nitrogen. Solvent was then allowed to evaporate from a freshly microtomed surface of the droplet. Finally, a replica was made of collapsed micelles raised proud from the frozen surface. In the second method (Booth et al. 1978), a drop of micellar solution was allowed to spread and evaporate on a carbon substrate, and 0s04 was used to selectively stain one of the blocks. 

Samples in the SEM can be examined "as is" for general morphology, as freeze fractured surfaces or as microtome blocks of solid bulk samples. Contrast is achieved by any one or combination of the following methods ... 

Solvent casting when microtoming is not desirable as a method of sample preparation. 

An embedding and polishing method can be used as an alternative to microtoming.48 In this case, a sample is placed in an uncured polymer resin, cured... 

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