Morphology observations structure

Periodic oscillations have been observed as a morphological instability in several systems grown under various conditions [148]. The correspondence of the observed structures with results of theoretical modelling [139,149] is striking. 

Figure 10. Four different ways of controlling the kinetics of polyol reduction and the corresponding morphologies observed for the Pt nanostructures. As the same amount of PVP was present in all four syntheses illustrated here, the striking differences in morphology were not caused by variation in the PVP concentration. It is assumed that the PVP molecules in these syntheses function only as a stabilizer to prevent the resultant nanoparticles from aggregating into larger structures. (Reprinted from Ref [270], 2005, with permission from Wiley-VCH.)...

Fig. 32 Schematic representation of molecular structure and morphology observed in PS-fo-PB-fc-PS linear and star-block copolymers. Oblique lines between blocks for LN2 and ST2 indicate tapered transition of dissimilar blocks. From [102], Copyright 2003 Wiley...

These three examples emphasize the idea that a complete description of amyloid fibril polymorphisms will only be achieved when 3D structures at atomic detail become available (Luhrs et al., 2005). Last but not least, since the various morphologies observed for amyloid fibrils are defining the end point of the assembly process, an essential need is to properly define the early stages of fibril formation, namely the oligomeric states of the peptide or protein in solution prior to assembly into fibrils. 

In the case of human amylin and Afi our understanding of the diversity in amyloid fibril architecture is the result of a recursive process, since the early morphological observations were followed by assessment of the assembly pathway which in turn yielded a better understanding of fibril polymorphism. However, this structural knowledge is secondary compared to the discovery of small oligomers, globular oligomers, and early protofibrils that appear to be extremely cytotoxic (Hartley etal., 1999 Lambert et al, 1998 Walsh et al, 1999). 

Fig. 7 Some peculiar morphologies observed for crew-cut micelles. Baroclinic tubes (a). Tube-walled vesicles (b). Large compound micelles insert shows their internal structure (c) and interconnected tubules or plumber nightmare (d) (images downloaded from http //ottomaass.chem.mcgill.ca/groups/eisenberg/). Adapted from [35]...

Covalent functionalization of the nanotubes also affects the voltammetric features the richer curve morphology observed in the case of pristine nanotubes reflects the more complex electronic structure of the pristine materials, compared to functionalized ones (Scheme 9.17), in agreement with recent calculations that suggested that functionalization significantly affects the low-lying electronic states of the nanotubes.61... 

The most common morphology observed in current mesophase carbon fibers of moderate modulus (55 to 75 Mpsi, 379 to 517 GPa) is a cylindrical filament with a random-structured core and a radial rim (12) Given the fracture section of Figure 3, with its scroll-like features, the core appears to be an array of +2ir and -ir disclinations. The radial rim of heavily wrinkled layers usually constitutes half or more of the cross section. 

The use of transmission electron microscopy in heterogeneous catalysis centers around particle size distribution measurement, particle morphology and structural changes in the support. Consideration is given to the limitations of conventional electron microscopy and how modifications to the instrument enable one to conduct in-situ experiments and be in a position to directly observe many of the features of a catalyst as it participates in a reaction. In order to demonstrate the power of the in-situ electron microscopy technique examples are drawn from areas which impact on aspects of catalyst deactivation. In most cases this information could not have been readily obtained by any other means. Included in this paper is a synopsis of the methods available for preparing specimens of model and real catalyst systems which are suitable for examination by transmission electron microscopy. 

Much of the information on hydrate processes has come from macroscopic studies, that is, from the observation of gas consumption, pressure drop, particle size measurements, or crystal morphology observations. However clathrate hydrates in many ways are unique materials that make it imperative that studies on the molecular scale are also carried out. For instance, several structures of hydrate may coexist, and often this is not obvious from phase equilibrium studies ... 

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