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Cubic conformation systems

A four-component capsule with a structure that conforms to a tetrahedron has been recently described by Venkataraman66 Specifically, triphenylamine ortho-tricarboxylic acid self-assembled via 12 O H-O hydrogen bonds to form a molecular tetrahedron (Fig. 36). The hydroxyl groups of the polyhedron participated in hydrogen bonds with single ethanol molecules embedded within each triangular face of each tetrahedron. The assembly crystallized in the rare cubic crystal system. The ability of the acid to form a tetrahedron was reminiscent of the ability of triphenyl-methanol to form a tetrahedron, which also forms inclusion compounds with solvent guests that occupy voids between the polyhedra.32... [Pg.45]

For a pure supercritical fluid, the relationships between pressure, temperature and density are easily estimated (except very near the critical point) with reasonable precision from equations of state and conform quite closely to that given in Figure 1. The phase behavior of binary fluid systems is highly varied and much more complex than in single-component systems and has been well-described for selected binary systems (see, for example, reference 13 and references therein). A detailed discussion of the different types of binary fluid mixtures and the phase behavior of these systems can be found elsewhere (X2). Cubic ecjuations of state have been used successfully to describe the properties and phase behavior of multicomponent systems, particularly fot hydrocarbon mixtures (14.) The use of conventional ecjuations of state to describe properties of surfactant-supercritical fluid mixtures is not appropriate since they do not account for the formation of aggregates (the micellar pseudophase) or their solubilization in a supercritical fluid phase. A complete thermodynamic description of micelle and microemulsion formation in liquids remains a challenging problem, and no attempts have been made to extend these models to supercritical fluid phases. [Pg.94]

Minutes are permitted to remain in the metric system for convenience or for historical reasons, even though they don t conform strictly to the rules. The minute, hour, and day, for example, are so customary that they re still defined in the metric system as 60 seconds, 60 minutes, and 24 hours— not as multiples of ten. For volume, the most common metric unit is not the cubic meter, which is generally too big to be useful in commerce, but the liter, which is one thousandth of a cubic meter. For even smaller volumes, the milliliter, one thousandth of a liter, is commonly used. And for large masses, the metric ton is often used instead of the kilogram. A metric ton (often spelled tonne in other countries) is 1,000 kilograms. Because a kilogram is about 2.2 pounds, a metric ton is about 2,200 pounds 10% heavier than an American ton of 2,000 pounds. Another often-used, non-standard metric unit is the hectare for land area. A hectare is 10,000 square meters and is equivalent to 0.4047 acre. [Pg.326]

Short homopolymeric chains restricted to a simple square lattice and to a simple cubic lattice have been studied by Chan and Dill [59-61]. For very small systems, all compact conformations could be enumerated. Not surprisingly, significant intrachain entropy loss occurs on collapse. Expand-... [Pg.208]

Fuel or vapor explosion hazards require installation of explosion vents. These can be blowout panels that also provide some insulating value and structural strength. A frequent practice is to provide a vent ratio of one square foot of surface to every fifteen cubic feet of dryer volume. This is illustrative only, and may serve as a first estimate. Venting systems must conform to NFPA68. [Pg.159]


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See also in sourсe #XX -- [ Pg.118 , Pg.119 ]




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