Open-book shape

These studies were then extended to the synthesis of palladium complexes of symmetric azines. In contrast to the above-mentioned compounds the di-jU-acetato complexes, 61, showed SmC, and in two cases, also nematic, mesophases. The jU-acetato ligands constrain the complexes to be nonpla-nar, and a novel type of structure based upon open-book-shaped molecules [143] has been proposed. With R optically active, a mixture of cis- and rrans-isomers was observed. 

Open-book shape structure of the chiral trans isomer of the -carboxylato palladium azines... 

The overall shape of the molecule is like a half-open book, as shown in Fig. 10.20. 

In principal, the complexes exist as a mixture of two isomers (anti and syn, Fig. 1), their proportion in the mixture depending on both the type of ligands and the intermetallic bridge and being evaluated by NMR. In general, when X = Cl, Br, I, SCN, the complexes are planar or slightly bent, and show mesomorphic properties. However, when X = OAc, the complex adopts the original roof or open-book molecular shape, and none of the palladium... 

The electronic properties of organic conductors are discussed by physicists in terms of band structure and Fermi surface. The shape of the band structure is defined by the dispersion energy and characterizes the electronic properties of the material (semiconductor, semimetals, metals, etc.) the Fermi surface is the limit between empty and occupied electronic states, and its shape (open, closed, nested, etc.) characterizes the dimensionality of the electron gas. From band dispersion and filling one can easily deduce whether the studied material is a metal, a semiconductor, or an insulator (occurrence of a gap at the Fermi energy). The intra- and interchain band-widths can be estimated, for example, from normal-incidence polarized reflectance, and the densities of state at the Fermi level can be used in the modeling of physical observations. The Fermi surface topology is of importance to predict or explain the existence of instabilities of the electronic gas (nesting vector concept see Chapter 2 of this book). Fermi surfaces calculated from structural data can be compared to those observed by means of the Shubnikov-de Hass method in the case of two- or three-dimensional metals [152]. 

B. A. Keiser s contribution to this book (the introduction to the section Preparation and Stability of Sols ) constitutes an excellent introduction to silica nucleation, polymerization, and growth in both aqueous and alcoholic systems for the preparation of silica sols. Yoshida s chapter (Chapter 2) focuses on industrial development in the preparation of monodisperse sols from sodium silicate and predicts further progress in the development of silica sols that have shapes other than spherical, such as elongated, fibrous, and platelet. Colloidal silica particles with these shapes show novel properties and open the possibility of new industrial applications. 

There are different design approaches to consider as reviewed in this book and different engineering textbooks concerning specific products. They range from designing an open top cubical box to a complex shape such as an aircraft wing structure. 

Usually the first powder characteristic that we are concerned about in our laboratory is specific surface area (more commonly referred to simply as surface area.) The surface area of a powder is a measure of its size, shape, and irregularity (such as the presence of voids that are open to the surface). There are several excellent books about surface area and its measurement.The most commonly used technique for determining powder surface area is the BET method using the adsorption of a monolayer of a gas such as nitrogen on the powder surface. The common unit of measure for surface area is mVg (area/unit mass). Most powders fall in the range of 1 to 50 mVg, with the vast majority of highly sinterable powders falling between 5 and 15 mVg. 

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