Packing arrangement

Other methods attempt to probe the stmcture of the foam indirectly, without directly imaging it. Eor example, since the Hquid portion of the foam typically contains electrolytes, it conducts electrical current, and much work has been done on relating the electrical conductivity of a foam to its Hquid content, both experimentally (15) and theoretically (16). The value of the conductivity depends in a very complex fashion on not only the Hquid content and its distribution between films and borders, but the geometrical stmcture of the bubble packing arrangement. Thus electrical measurements offer only a rather cmde probe of the gas Hquid ratio, a quantity that can be accurately estimated from the foam s mass density. 

Apparent Density. This term refers to the weight of a unit volume of loose powder, usually expressed in g/cm (l )- The apparent density of a powder depends on the friction conditions between the powder particles, which are a function of the relative surface area of the particles and the surface conditions. It depends, furthermore, on the packing arrangement of the particles, which depends on the particle size, but mainly on particle size distribution and the shape of the particles. 

Molecular mechanics (MM) energy minimiza tion indicates that the two modes lead to monolayers exhibiting different types of packing arrangements, but comparable in their ground state energies. (The monolayer resulting from the mode is more stable by 2.5 kJ/mol (0.6 kcal/mol))... 

FIG. 10-97 Typical packing arrangement, using metallic packing, for high-pressure cylinders. 

Obviously, properties like the shear modulus might well be different for close-packed planes and cube planes, because the number of bonds attaching them per unit area is different. This is one of the reasons that it is important to have a method of describing various planar packing arrangements. 

Figure 4.3 In most a/p-barrel structures the eight p strands of the barrel enclose a tightly packed hydrophobic core formed entirely by side chains from the p strands. The core is arranged in three layers, with each layer containing four side chains from alternate p strands. The schematic diagram shows this packing arrangement in the a/p barrel of the enzyme glycolate oxidase, the structure of which was determined by Carl Branden and colleagues in Uppsala, Sweden.

The transparency and refractive power of the lenses of our eyes depend on a smooth gradient of refractive index for visible light. This is achieved partly by a regular packing arrangement of the cells in the lens and partly by a smoothly changing concentration gradient of lens-specific proteins, the crystallins. 

Lim, W.A., Sauer, R.T. Alternative packing arrangements in the hydrophobic core of X repressor. Nature 339 ... 

The different forms of carbynes were assumed to be polytypes with different numbers of carbon atoms in the chains lying parallel to the hexagonal axis and different packing arrangements of the chains within the crystallite. Heimaim et al [23] proposed that the sizes of the unit cells were determined by the spacing between kinks in extended carbon chains, Fig. 3A. They were able to correlate the Cg value for the different carbyne forms with assumed numbers of carbon atoms, n (in the range n = 6 to 12), in the linear parts of the chains. 

Spontaneous combustion Any combustion that takes place without a source of ignition due to the nature of the material and its packing arrangements. 

Figure 6.2 Basal plane of a-rhombohedral boron showing close-packed arrangement of B 2 icosahedra. The B-B distances within each icosahedron vary regularly between 173-179 pm. Dotted lines show the 3-centre bonds between the 6 equatorial boron atoms in each icosahedron to 6 other icosahedra in the same sheet at 202.5 pm. The sheet-s are slacked so that each icosahedron is bonded by six 2-centre B-B bonds at 171 pm (directed rhombohedral ly, 3 above and 3 below the icosahedron). B12 units in the layer above are centred over 1 and those in the layer below are centred under 2.

The metals are silvery in appearance (except for Eu and Yb which are pale yellow, see p. 112 and below) and are rather soft, but become harder across the series. Most of them exist in more than one crystallographic form, of which hep is the most common all are based on typically metallic close-packed arrangements, but their conductivities are appreciably lower than those of other close-packed metals. 

In principle, the odd-even effect can be explained from the differences in the packing arrangement of the... 

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