Transmission electron microscopy Subject

Substrate Characterization. Test coupons and panels of 7075-T6 aluminum, an alloy used extensively for aircraft structures, were degreased In a commercial alkaline cleaning solution and rinsed In distilled, deionized water. The samples were then subjected to either a standard Forest Products Laboratories (FPL) treatment ( 0 or to a sulfuric acid anodization (SAA) process (10% H2SO4, v/v 15V 20 min), two methods used for surface preparation of aircraft structural components. The metal surfaces were examined by scanning transmission electron microscopy (STEM) In the SEM mode and by X-ray photoelectron spectroscopy (XPS). 

Powdered, particulate MCM-41 molecular sieves (Si/Al = 37) with varied pore diameters (1.80, 2.18, 2.54 and 3.04 nm) were synthesized following the conventional procedure using sodium silicate, sodium aluminate and C TMAB (n = 12, 14, 16 and 18) as the source materials for Si, A1 and quaternary ammonium surfactants, respectively [13]. Each sample was subjected to calcination in air at 560 °C for 6 h to remove the organic templates. The structure of the synthesized material was confirmed by powder X-ray diffraction (XRD) and by scanning/transmission electron microscopy. Their average pore sizes were deduced from the adsorption curve of the N2 adsorption-desorption isotherm obtained at 77 K by means of the BJH method (Table 1). 

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. 

The case of Cryptosporidium species substantiates at best the common features examined in the precedent section. These atypical coccidians, responsible for severe chronic diarrhea in immunocompromised patients and for acute diarrhea in immunocompetent subjects (Chalmers and Davies 2009), penetrate enterocytes remaining at the microvillous surface level (Fig. 1). This situation is usually qualified as intracellular - extracytoplasmic or, more recently, epicellular (Valigurova et al. 2008), as the parasites develop at the level of the brush border of microvillus. A feeder organelle can be observed in the zone of contact with the host-cell cytoplasm using transmission electron microscopy (TEM) (Valigurova et al. 2008). 

Transmission electron microscopy (TEM). Conclusions drawn from the above characterization studies were further corroborated by direct observation of model catalysts. These model catalysts were prepared by depositing the active components directly on gold microscope grids coated with a planar silica substrate. After deposition of the precursor salts, the grids were placed in a quartz flow reactor where in order to mimic the preparation of the real catalysts, they were subjected to the same pretreatments, as described in the catalyst preparation section. 

Fibers of the control and selected chemically modified cottons were examined techniques of optical microscopy described previously.Ultra thin cross sections of the fibers were subjected to layer expansion by polymerization of methyl methacrylate and to solubility tests in 0.5 M cupriethylenediamine (cuene) and were examined by the techniques of transmission electron microscopy as previously reported.Scanning electron micrographs of fibers of selected samples before and after subjection to various solvents were also obtained. 

Fig. 44. Microciystals of Valonia macrophysa cellulose subjected to the action of celluloses (CeI7A from Humicola insolens) consisting of a hydrolytic core, a cellulose-binding module, and a linker that binds the two enzymic components. The reducing end of the cellulose chains is indicated. R, transmission electron microscopy of the cellulose microciystals before and after the enzyme aetion indieates that Cel7A induced a...

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