Columnar clusters

BSUs at random BSUs clustering Columnar liquid crystals Lj < 1 nm Mosaic formation Column coalescence L2 increases ... 

Thin film technology is becoming one of the important technologies today. While there are infinite varieties of thin film fabrication methods, most amorphous thin films seem to exhibit fractal-like atomic structures. Depending on the fabrication conditions, a thin film grows on the substrate into columnar structures with many voids interdispersed in the thin film.80 These structures can be seen in the field ion microscope, and compositional variation can be analyzed with the atom-probe. In addition, formation of atomic clusters inside the thin film can be substantiated with the observation of a large fraction of cluster ions in field evaporation by the atom-probe. 

The electron-rich trinudear Au3 (bzim) 3 and Au3 (carb) 3 react with F6 to yield the sandwich clusters [n Au3(bzim)3 2](PF6) 29 and [n Au3(carb)3 2](PF6) 30 [54]. The cation of both compounds contains atom which interacts in a distorted trigonal prismatic coordination with six Au(I) atoms from two cyclic Au3C3N3 moieties at Au- distances ranging from 2.971(1) to 3.107(1) A, indicative of appretiable metal-metal interaction. Two Au(I) atoms on each planar trinudear unit are involved in intermolecular aurophilic bonding interactions [Au-Au 3.109(1)/3.066(1) A in 29 3.059(1)/3.052(1) A in 30], thus resulting in an infinite columnar chain with a BBABBA- pattern (Figure 4.11). 

The cervical section presented in Fig. 10.7 has been diagnosed as a rare form of neoplasma known as villoglandular adenocarcinoma. Characteristic cytologic features of this condition include the presence of long villous fronds and papillae lined by columnar cells with intact cytoplasmic borders and minimal atypia.32 Three-dimensional ball-like clusters of cells with smooth intact communal cytoplasmic rings are also associated with this condition.32... 

Their growth is characterized by the sequence of proliferation, confluency, differentiation. Morphologically they reveal typical brash border cells with columnar shape and microvilli, polarization, cubble-stone morphology with flower-like clusters (Pinto et al. 1983 Hidalgo and Borchardt 1989), presence of... 

Key words Cluster, whisker, columnar structure, vapor-liquid-solid mechanism... 

In order to eliminate columnar structures it is necessary to increase the migration ability of atoms and molecules on the surface and also to remove the involvement of clusters in the process of growth. To prevent the participation of clusters and nanoparticles during growth and in order to create the conditions for highly perfect ZnO layers s mthesis, we explored the possibility of ZnO layers growth according to VLS-model. 

The mechanism of growth of columnar structure ZnO layers assumes the presence of nanosized clusters in the reagent flow and that the formation of ZnO layers can be described by a model close to the one of Witten-Sanders. Increase of target-to-substrate distance leads to the decrease of the number of aggregates in the flow near the substrate and to the improvement of the structural perfection of ZnO layers. 

Figure 29 Lowest-energy structures for (Si02J v clusters. The dashed line separates columnar and disklike clusters. Reproduced with permission of the American Physical Society from 114...

In addition to vertical bundles of myelinated axons, the cerebral cortex of monkeys (e.g., DeFelipe et al., 1990) and of humans (e.g., del Rio and DeFelipe, 1995) also contains vertically oriented bundles of unmyelinated axons that are referred to as horsetails. These horsetails are the axonal plexuses of the inhibitory double bouquet cells and can be demonstrated in monkey neocortex by immunolabeling with antibodies to calbindin and tachykinin. As shown by DeFelipe et al. (1990), in the monkey these axonal bundles are widespread and form a regular columnar system descending from layer 2 to layers 3-5. The bundles are most evident in tangential sections taken at the level of layer 3, where they can be seen to have a center-to-center spacing of 15-30 fim. In a later study of the calbindin labeled double bouquet cells in monkey striate cortex, Peters and Sethares (1997) showed that there is one double bouquet cell, and therefore one vertically oriented double bouquet cell axonal plexus, or horsetail, per pyramidal cell module (Fig. 7). Within layer 2/3 the double bouquet axons run alongside the apical dendritic clusters, while in layer 4C they are closely associated with the vertical myelinated axonal bundles. DeFelipe et al. (1989 1990) proposed that the axon terminals of the double bouquet cell synapse with the shafts and spines of basal dendrites and oblique shafts of apical dendrites of pyramidal cells, but the exact role of these vertical bundles of inhibitory axons is not known. It is likely that they constitute a vertical inhibitory system that acts upon pyramidal cells within the minicolumns. 

Grossly the tumors are white, gray, red, brown, or yellow and may be localized or fill the entire middle ear, often encasing the ossicles. Microscopically, MEAs are characterized by architectural diversity and cytologic uniformity. Some are composed of well-formed glands, sheets of cells, small cells/or clusters, short trabeculae, or a combination of these patterns (Eig. 9.31). Individual cells vary from round or cuboidal to columnar... 

The base plan unit-cell projection (Figure 2) shows the positions of the water molecules in the unit-cell as deduced from an analysis of the equatorial x-ray diffracted intensities for a fiber diagram recorded at about 50X relative humidity. The water molecules cluster in distinct areas and form a helical column whose symmetry matches that of the xylan chains. In fact, the water of hydration may dictate the symmetry of the xylan chains. The energetically (theoretical) most stable conformation of the xylan chain involves twofold symmetry, whereas in the hydrated crystalline environment, as deduced from x-ray diffraction, the xylan chains possess three-fold symmetry. The water molecules stabilize the three-fold structure by the formation of hydrogen bonds. This structure is an example of columnar hydration which allows a symmetric... 

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