Cuboid

In Figures 9-13 and 9-16 the artificial neurons have been plotted as circles. In order to visualize the weights as well, we will now plot the neurons as columns, consisting of cuboids, where each cuboid represents a weight. 

Heywood [Heywood, Symposium on Paiticle Size Analysis, lust. Chem. Engrs. (1 7), Suppl. 25, 14] recognized that the word shape refers to two distinc t charac teiistics of a particle—form and proportion. The first defines the degree to which the particle approaches a definite form such as cube, tetr edron, or sphere, and the second by the relative proportions of the particle which distinguish one cuboid, tetrahedron, or spheroid from another in the same class. He replaced historical quahtative definitions of shape by numerical shape coefficients. 

Figure 9.5. Electron micrograph of a superalloy, showing ordered (gamma prime) cuboids dispersed epitaxially in a disordered (gamma) matrix (courtesy of Dr. T. Khan, Paris).

Assume that liver cells are cuboidal in shape, 20 ym on a side. 

Figure 23.8 Trinuclear. M-.M bonded species of Mo" and W. (a) (b) and (c) are alternative representations of the -MjOij unit (a) emphasizes its relationship to the edge-sharing octahedra of the Mj group in polymetallate ions (b) shows the (rrj-O) (rrr-Olj bridges and M-M bonds of its MiOs incomplete cubane" core and (c) emphasizes its triangular centre by viewing from the unoccupied comer of the cuboid (d) and (e) offer the same perspective as (c) but of (Mj02(02CR)6(H20)3] and (Mjirrj-X)(rti-OR)(OR)9] stmetures respectively.

Transmission electron microscopic observaiion reveals various morphologies of precipitates depending upon the constituents and composition of an alloy system, history of heat treatments etc. Typical examples are spherical precipitates found in Nl-Cr-Al system and cuboidal precipitates in Fe-Mo system [1]. The first question raised is what determines the shape of a precipitate. 

A summary of the Fe-Fe and Fe-S distances in cuboidal [Fe3S4] ° centers as deduced by X-ray crystallography and EXAFS, is given in... 

Metric Data for Cuboidal [Fe3S4] Clusters as Determined by Crystallographic Studies ... 

The [3Fe-4S] core is now considered an unique basic iron-sulfur core whose structure was determined in D. gigas Fdll 56, 84) (as well as in aconitase 85-87) and A. vinelandii Fd (57, 59, 80)). The cluster in these proteins have Fe-Fe and Fe-S distances around 2.8 and 2.2 A and the core described as a cuboidal geometry with one comer missing (Fe S stoichiometry of 3 4). 

Trinuclear Cuboidal and Heterometallic Cubane-Type Iron-Sulfur Clusters New Structural and Reacticity Themes in Chemistry and Biology R. H. Holm... 

This supramolecular approach has been used as a way to facilitate the crystallization of cuboidal aqua ions and to capture single intermediates present in complex solution mixtures. For example, [M3Q4Clx(H20)9.x] (Q = S, Se) supramolecular adducts have been isolated for x =1-5 from aqueous HCl solutions by varying the acid concentrations where the aggregates contain in each case only one of all possible isomers [46]. In addition to the hydrogen bonds, other kinds of interactions, namely C1---H20, C1---C1 and Q---Q contacts, are also involved in the network propagation. This supramolecular approach has also been efficiently employed for the crystallization of a large number of aqua complexes within the [M3M Q4] cubane-type family, where M is a transition or post-transition metal [47]. 

In a series of studies of carefully prepared catalysts of Pt on silica gel (7,10-12) we have shown that the Pt particles are equi-axed, (and de-finitely not cuboidal as is often assumed) that the size (or percent metal exposed) agrees with results from hydrogen chemisorption, and that the particles are free of microstrain faults or twins, except when the average size is similar to the pore size of the support. In this latter case, the particles are elongated, and there is microstrain, probably due to differ-... 

Figure 6.8 Scanning electron micrographs of magnesium ammonium phosphate mortar III (Abdelrazig, Sharp El-Jazairi, 1989) (a) after 1 hour, low magnification, (b) after 1 hour, high magnification showing needle-like and cuboid crystallites.

Where the terms have been previously described. As a first approximation, we have assumed here that the lateral space is a rectangular slit between cuboidal cells. The porosity, the fractional area of the cell monolayer in the paracellular space, is calculated as... 

Three principal cell types exist in the corneal epithelium, namely, superficial cells, wing cells, and basal cells. A single layer of cuboidal basal cells is the sole site of cell division in the corneal epithelium. By necessity, these cells have more prominent mitochondria and Golgi apparatuses and hence high levels of metabolic and synthetic activities. Immediately above the basal cells is a zone comprising two to three layers of wing cells that are in an intermediate state of differentiation. 

Fig. 1.6 (A and B) Scanning electron micro- implantation in the bone marrow showing for-graphs of the porous hydroxyapatite-collagen mation of new bone (white asterisk) attached nanocomposite scaffolds at different magnifi- directly to the nanocomposite (asterisk). Arrows cations. Arrowheads in B indicate the hydroxy- indicate cuboidal osteoblasts on the surface of apatite nanocrystals on the collagen fibrils. new bone. Adapted from [94], reproduced by Histology at (C) 1 week and (D) 4 weeks after permission of Wiley-VCH.

Figure 87 The structure of the cuboidal complex [Ca(THF)(CH[P(C6H4Me-4)2]C6H40-2)]4 168.

Two equiv. of 6,6-di(cyclopropyl)fulvene react at 60 °C over a period of a week with Ca[N(SiMe3)2]2-(THF)2 bis in THF to yield the metallocene 170. The heteroleptic amido complex 171 is detected as an intermediate with 111 and 13C 1H NMR spectroscopy. A 1 1 reaction of the calcium amide and 170 also produces 171 in solution, an equilibrium involving these three derivatives exists (Equation (30)). The calcocene 170 crystallizes at — 20 °C from THF as colorless cuboids. The metal center is surrounded by the four ligands in a distorted tetrahedral manner, and the cyclopentadienyl group and the propylidene fragment are coplanar with each other.393... 

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