Microscopic origin

The microscopic origin of x and hence of Pis the non-unifonnity of the charge distribution in the medium. To lowest order this is given by the dipole moment, which in turn can be related to the dipole moments of the component molecules in the sample. Thus, on a microscopic quantum mechanical level we have the relation... 

The force between two adjacent surfaces can be measured directly with the surface force apparatus (SEA), as described in section BT20 [96]. The SEA can be employed in solution to provide an in situ detennination of the forces. Although this instmment does not directly involve an atomically resolved measurement, it has provided considerable msight mto the microscopic origins of surface friction and the effects of electrolytes and lubricants [97]. 

Decomposition of SE. Some insight into the microscopic origin of the SE can be obtained by examining the separate contributions to the kinetic and potential energy [3]. 

As for direct emulsions, the presence of excess surfactant induces depletion interaction followed by phase separation. Such a mechanism was proposed by Binks et al. [ 12] to explain the flocculation of inverse emulsion droplets in the presence of microemulsion-swollen micelles. The microscopic origin of the interaction driven by the presence of the bad solvent is more speculative. From empirical considerations, it can be deduced that surfactant chains mix more easily with alkanes than with vegetable, silicone, and some functionalized oils. The size dependence of such a mechanism, reflected by the shifts in the phase transition thresholds, is... 

As reported in this chapter, the microscopic origin of both compressibility and elasticity of dense emulsions is rather well understood. Emulsions have elastic properties arising from either surface tension or surface elasticity and plasticity. Some protein-stabilized emulsions obey the same phenomenology as solid-stabilized emulsions they exhibit substantially higher osmotic resistances and higher shear moduli than surfactant-stabilized emulsions [38 0]. Moreover, they are strongly resistant to water evaporation. Proteins possess the ability to form... 

Since the issue of order/disorder versus (or with) displacive aspects has remained an active field of research, most of the chapters presented in this book are devoted to it. In addition, new fields of applications are reviewed, since material optimization has considerably enlarged this area. A new aspect of ferroelectricity has been discovered recently by the finding of isotope-induced ferroelectricity in the quantum paraelectric SrTiOa. Here conclusive ideas about its microscopic origin are still missing and also the experimental situation remains controversial, since the symmetry of the low-temperature phase is unclear. But, there seems to be stringent evidence that polar clusters are... 

In this section, we will examine the microscopic origins of viscosity for each material type, and we will see how viscosity is much more complex than simply serving as a proportionality constant in Eq. (4.3). Ultimately, we will find that viscosity is not a constant at all, but a complex function of temperature, shear rate, and composition, among other things. 

Typical point defects present at the Si02 surface are the so called E centres, holes trapped at oxygen vacancies, and Si dangling bonds. These latter defects are particularly important when present at the Si/SiOz interface because they markedly affect the electrical properties of electronic devices. These defects, which are also known as Pb centres, have been widely investigated in the past. Recently however, the microscopic origin of these defects has been unravelled by means of a sophisticated UHV-ESR system by Futako et al, 178 who elucidated the formation processes of interface dangling bonds (Pb centres) during the initial oxidation of a clean Si(lll) surface. After oxidation of one or two Si layer(s), the... 

In recent years, most rotational anisotropic data for both metals and semiconductors have been discussed in light of Tom s model [67, 68] and from the theory of Shen [78]. No assumption is made about the microscopic origin of the bulk and surface nonlinear polarization. This phenomenological model predicts a simple functional dependence of the SH intensity on the angle of rotation of the sample about the surface normal... 

Investigation of the microscopic origin of these TLSs has demonstrated the feasibility of modulating resonance shifts in a single molecule by interrogation of neighboring solvent molecules coupled to the system.1158 In poly(methyl methacrylate) doped with free base phthalocyanine and small amounts of water, it has been shown that reorientation of nearby water molecules is the source of spectral diffusion observed in the phthalocyanine. 

Equations (1.3) and (1.4) describe the mean properties of the dielectric. This macroscopic point of view does not consider the microscopic origin of the polarization [3], The macroscopic polarization P is the sum of all the individual dipole moments pj of the material with the density Nj. 

The microscopic origin of the collective modes has been identified since a long time. They are reported here with the corresponding typical correlation times (CT) reorientation modes (this is the so-called Debye region, CT > 10-12s), libration modes (rotations impeded by collisions, CT = 10 13s), atomic motions (vibrations, CT = 10-14s), electronic motions (CT = 10 16s). When the frequency of the external field increases, the various components of the polarization we have introduced here become progressively no longer active, because the corresponding motions of the solute lag behind the variation of the electric field. 

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