Electron microscopy data

FIGURE 7.3. Transmission Electron Microscopy Data for in-tact (a c) and activated (b d) Pt/Si02 catalysts. Reprinted with permission from 7. Am. Chem. Soc. 2003,125,14832—14836. Copyright 2003 American Chemical Society. 

Crystal structure determination from electron microscopy data... 

Transmission Electron Microscopy Transmission electron microscopy data were obtained by personnel in the Ultrastructure Laboratory at the Virginia-Maryland College of Veterinary Medicine using a JEOL lOOCX-II transmission electron microscope. Samples were imbedded in Poly-bed 812 epoxy resin and cured at 50-60°C for 2-3 days. Samples were then sectioned to between 800 and 1000 on either a Sorval MT2B or an LKB IV Ultramicrotome using glass knives and were placed on 200 mesh copper grids. 

Hydroxotitanate anion, however, has never been detected in the course of hydrolysis of titanium alkoxides. On the basis of electron microscopy data, Diaz-Guemes et al. [477] suggested the two-step adsorption mechanism for the above reaction. According to his assumption hydrolysis of titanium alkox-ide results in a gel of hydrated titanium oxide, which is further diffused by M2+ cations to form crystalline MDTi03 ... 

Figure 11. Electron microscopy data for Nu-13. A transmission electron micrograph demonstrates the presence of three crystal morphologies. Lattice parameters derived from electron diffraction patterns for each crystal type confirm the composition of Nu-13 as a mixture of (a) ZSM-12,...

Figure 9. Number of particles as function of conversion in the course of EA polymerization, corrected for electron microscopy data (see Figure 8)...

When considering metal-support interaction effects, the whole set of Electron Microscopy data presented in the previous section point out some important differences between the behaviour of noble metal catalysts supported on ceria and that of titania-supported catalysts. Much higher reduction temperatures are required in the case of ceria-type supports to observe nanostructural features similar to those described for the so called SMS I efTect. 

Kim D. and Hopke P. K. (1988) Classification of individual particles based on computer-controlled scanning electron-microscopy data. Aerosol Sci. Technol. 9, 133-151. 

The mesoporosity of these materials has been established by BET measurements and gas adsorption experiments. As the chain length of the surfactant was increased from Cs to G 5, the amount of adsorbed benzene was increased, indicating that there was a relationship between the size of the surfactant and the amount of gas adsorbent taken up by the MCM-41 material. In terms of a comparison to zeolite materials, experiments were done at 60 torr pressure and at 25< C. llie US-Y zeolite sample had an uptake that was about 4 times less than that of MCM-41. The above mentioned MCM-41 materials all show pore size distributions with broad bands centered around 40 A. The pore size distribution measurements are a true indication of the size of the pores and can be used to verify the existence of mesopores. Further evidence of mesoporosity comes from X-ray powder difraction experiments which were done to determine the crystallinity of these materials. The position of the (100) reflection was found to correlate with the amount of uptake by the different materials, or in therwords, with the mesoporosity of these systems. Pores of the MCM-41 materials were shown to form in a hexagonal shape by using high resolution transmission electron microscopy data. 10... 

The Raman scattering in Si nanociystals non-unifonnly distributed in Si02 (fused quartz) and AI2O3 (sapphire) matrices was studied. The mean diameter of the nanocrystals in Si02 is detemiined that is consistent with electron microscopy data. In case of nanocrystals embedded in AI2O3 Raman shifts indicate existence of a compressive stress that suppress Si nanociystal photoluminescence. 

The first detailed structure of a membrane protein was made by Henderson and Unwin [4], They determined the structure of bacteriorhodopsin from electron microscopy data from two-dimensional crystals of the protein. Seven transmembrane a-helices were identified, tilted about 20 towards the bilayer plane. The tilt by itself indicates a catenoid-like shape of the hydrophobic region through the lipid bilayer. 

From X-ray and electron microscopy data (21). it was found that the ZnSt in S-EPEW phase separates into crystalline domains of less than 500 nm. It was also inferred from the data that the interactions between the sulfonate groups and the ZnSt occur on preferred crystal planes. In the context of stress relaxation results, it was proposed that the long cell axis of ZnSt lies at 90 to the stress axis, and that relaxation of the stress occurs by "interaction hopping . Sane stress relaxation studies of ZnSt plasticized S-EPDM were also reported by Granick (35). 

Electron microscopy data on such catalysts show the average diameters of the metal clusters to be of the order of 10 A or lower. Clusters of this size necessarily consist almost exclusively of surface atoms. The stoichiometry of the strongly chemisorbed fraction thus appears to be close to one hydrogen atom per surface metal atom for platinum-iridium catalysts containing equal amounts of the two metals. If this stoichiometry were precisely correct, a value of H/M from Figure 4.20 would be a direct measure of the metal dispersion, that is, the ratio of surface atoms to total atoms in the metal clusters. 

An illustrative example of combining protein modeling and electron microscopy data is the case of the apoptosome, an Apaf-1 cytochrome c complex that activates procaspase-9 [40]. The data obtained in this work helped to decipher the exact mechanism of a very important apoptosis triggering mechanism. Another interesting example is the use of computational and biochemical methods to conduct structural analyses of the seven proteins that compose the core building block of the nuclear pore complex [41]. 

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