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There are three parameters in Eq. (2) which determine the behavior of the model and these can, within limits, be determined without reference to surface order. We took J 2 Mi as -0.2, quite close to the preferred value of -0.25 suggested in Ref. 7. To illustrate best the contrast between results from the bulk and from the surface, we adjusted J ± so that the calculated points for the bulk order parameter agree with experiment 4 up to the experimental transformation temperature. This gave J 1 /k = 23TK, a value about 7% higher than would have been obtained by the procedure of Ref. 7. Finally we let AE = 2.5^, corresponding to a constant average surface composition.In Fig. 4 we show the average of the order parameters for the two topmost Cu-Au layers, for the two boundary conditions of the surface model, together with the measured surface order and the calculated bulk order as a function of temperature. It appears from the figure that the difference between the observed behavior of the longrange order parameter at the surface and that in the bulk can be explained by a simple model involving only nearest-and next-nearest-neighbor interactions which are the same for both surface and bulk. Furthermore, it is evident from the analysis that consideration of a region of accommodation between surface and bulk is a necessary Considerable interest exists in examining the properties of both organic and inorganic structures which are highly anisotropic and can be visualized as containing one-dimensional chainsmetallic "spines"-surrounded by a matrix whose properties are highly important in determining the transport properties of that system. The or-feature of any model meant to describe the phenomenon of long-range order at a crystal surface.The temperature dependence of the electrical conductivity and Seebeck coefficient for the polymer chain system (SN) X has been measured along the chain axis from 4.2 to 300°K. The data show the system to be metallic over the entire temperature range studied, with a small conductivity maximum at ~33°K.

New measurements of electrical conductivity along the b axis of tetrathiafulvalenium-tetracyanoquinodimethanide (TTF-TCNQ) are combined with published results to provide a comprehensive summary including approximately 600 samples studied at 18 different laboratories. The magnitudes of these measured conductivities do not necessitate the assumption of superconducting fluctuations or any other collective state in which the conductivity exceeds the limitations of single-particle scattering. Since an adequate theory of the limitations of single-particle scattering for TTF-TCNQ does not exist at present, experiment alone does not rule out the possibility that collective effects may somewhat enhance or suppress the conductivity.The dc electrical conductivity of tetrathiafulvaienium -tetracyanotiuinodimethanide (TTF-TCNQ) was first reported by Ferraris, Cowan, Walatka, and Perlstein' in 1972. Since that time a number of workers have carefully studied the conductivity in this organic charge-transfer salt. Although the results are not in complete agreement and measurements are continuing in some groups, we would like to summarize the substantial body of work that has been completed. The observed magnitude of the conductivity appears to be com-parable to that in common metals and thus, from the limited point of view of an effective mean free path, consistent with a possible contribution to the transport properties from single-particle electron scattering.The original results of Ferraris etal. indicated that TTF-TCNQ was the most highly conducting organic compound known. Its dc conductivity rose with decreasing temperature like a metal and was highly anisotropic. The observed anisotropy was consistent with the crystal structure of other 13 5105

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Some of the main interrelationships thot govern heat and mass transfer i n dispersions are considered. Qualitative and quantitative analyses of the effects of holdup, average residence time, surface active agents, viscosity, and average particle size on transfer rates are made for two major domains. I n the first domain a convective mass transfer model is formulated Most theoretical studies of heat and mass transfer in dispersions have been limited to studies of one phase and to the case of a steady motion of a single spherical droplet under the influence of gravity in a clean system. It is clear, however, that swarms of suspended droplets which are entrained by turbulent eddies have relative velocities (with respect to the continuous phase) which are different from those derived for the case of a steady rise of a single droplet. This is mainly due to the fact that in the case of a swarm of particles, the distributions of velocities, temperatures, and concentrations in the vicinity of one particle are influenced b its neighbors. It is therefore logical velocities and transfer rates depend on quantities characterizing a swarm of droplets. For the case of uniformly distributed particles, the dispersed hase volume fraction are such quantities.In this study we first consider the main interrelationships that govern heat and mass transfer in dispersions and then we make qualitative and quantitative analyses of the effects of holdup, contact time, surface active agents, viscosity, and particle size on the transfer rates. to assume that in t i e case of dispersions, the relative @, particle size distribution, and resi B ence time distribution (1) where the subscript P refers to each of the corresponding phases involved. In the case of dispersions, where swarms of particles are moving with different local velocity components relative to an arbitrary moving fluid, the question arises as to the function of 6, the velocity vector relative to an arbitrary moving continuous phase. In general, the magnitude of the local relative velocity of a drop or bubble to a continuous phase in a dispersion may be expressed as (16,11)Benjamin Gal-Or is at the

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