General Phenomenology

The phenomenology described in the preceding section is general since it has been reproduced using different ionic surfactants, such as alkyl sulfonates or alkyl quaternary ammonia [11,12,16]. Villa et al. [17] have also investigated coalescence phenomena in W/OAV globules. They developed a capillary microscopy technique 

The previous experimental observations reported in the preceding text are, at least to a certain extent, in agreement with the well-known Bancroft rule. Indeed, a double W/O/W emulsion turns into a simple direct one when a sufficient quantity of the water-soluble surfactant is added. Similarly, by shaking a 1 1 mixture of water and oil, each phase containing one of the two types of surfactants, a direct emulsion is obtained if the aqueous phase contains a large amount of water-soluble 

---

Petukhov A V 1995 Sum-frequency generation on isotropic surfaces general phenomenology and microscopic theory for ]ellium surfaces Phys. Rev. B 52 16 901 -11... 

A Generalized Phenomenological Transport Model and Simple Consequences... 

Berry, R. S. (1980), A General Phenomenology for Small Clusters, However Floppy, in Quantum Dynamics of Molecules, R. G. Woolley (Ed.), Plenum, New York. 

Johnson proposed a more general set of linear dynamic equations taking into account a mass coupling in the inertia terms [73]. This theory is based on a general phenomenological scheme originally proposed by Biot to describe dynamics in porous media [74,75], Johnson claimed that the inertia terms, the left hand sides of Eqs. (6.1) and (6.2), should in principle be replaced by... 

In the following sections we will discuss the various theories which have been proposed and confront them with the general phenomenology of the stress-strain behaviour. 

The first term D dQ/dz) represents the diffusion, the second term D ZjQF/flT) (dcp/dz) the migration of a component. Thus, the Nernst-Planck equation is an approximation of the more general phenomenological equation. 

This article covers the activation of supported catalysts. It examines the formation of the final catalysts, as achieved by three categories of treatment calcination, reduction, and sulfidation (more precisely reduction sulfidation). Detailed studies of these three categories of processes did not lead to an equally detailed analysis. Outside very general (phenomenological) observations, very little is known concerning the calcination of supported precursors. By contrast, some particular systems have been studied in some detail in reduction (e.g. NiO/support for activation to Ni/support) or sulfidation (Coj(Moj,Or/y-Al203 to sulfides). 

This section provides a basic explanation of the underlying physical processes that control localized corrosion in order to lay the foundation for an understanding of the tests that are discussed in the next section. The manifestations of these physical processes through electrochemically measurable quantities are then discussed. Some generalized phenomenology is presented through illustrative examples from the literature. Full mechanistic understanding of localized corrosion has not yet been achieved. Information on the various models proposed can be found in review articles (11,12) and corrosion texts (13,14). 

This direct initiation process is certainly favoured by the very pronounced basicity of the oleftn used and moreover must be considered peculiar to antimony-based Lewis acids which combine a marked strength and the capacity of undergoing facile reduction. It is therefore a specific event which obviously does not explain the more general phenomenology of direct initiation in cationic polymerisation. 

If the rate-determining step of this process is the formation of the carbenium ion, a second or third order dependence on Lewis acid concentration would be expected depending on whether the species MtX iMtXji/+j is in the form of ion pairs or free ions. This third mechanism is not inconsistent with the general phenomenology of direct initiation, but no specific evidence in its favour is available. 

Photoluminescence can be defined as the radiation emitted from a molecule or a solid which, after it has absorbed energy from an external source and been transferred into an electronic excited state, returns to its ground electronic state. Although it can be said that photoluniinescence consists of both fluorescence and phosphorescence, the distinction between the two is generally phenomenological, but, as shown later, a more theoretical distinction can be proposed. This review is presented in the context of photoluminescence as an analytical tool, the basic principles of which can... 

Doi and Ohta (1991) derived very similar expressions for cri2, A/i, N2 for the elastic stresses of emulsions in step shearing strains. Larson (1997) has shown that Eqs. (9-57a) and (9-57b) can be derived as an approximation from a general phenomenological film model for affinely stretching, constant-tension interfaces thus cti2, N, and N2 can all be represented by the simple tensor expression... 

In the further elaboration a general phenomenological framework for wetting can be developed. Because of its thermodynamic nature, this framework is macroscopic and static it refers to equilibrium or to reversible processes. So, the kinetics of wetting cannot be analyzed in this way and only one contact angle, the equilibrium angle, can be considered. It remains an issue how this thermodynamic contact angle relates to the one that is physically measurable. Another typical feature is that interfaces are always taken to be at equilibrium with the adjacent... 

This behavior of BDD and BDD/Ir02 electrodes can be explained on the basis of the generalized phenomenological model, previously proposed for oxygen evolution in acidic medium [10,14,15]. According to this model (Figure 11), the initial step is represented by the oxidation of water molecules to form adsorbed hydroxyl radicals (reaction a). Next, two different mechanisms for the oxygen... 

The model, based on Hnear, irreversible thermodynamics, constitutes a more general phenomenological approach, appHcable to systems with either class of membranes, multiple solutes, and driving forces involved. It includes component and overall mass balances, mass-transfer rates, local equilibrium relations, and electroneutrahty constraints. 

A final and very important general phenomenological conclusion is that the conventional form of the Tafel equation with slope b = RT/aF with a constant is rarely observed at least for those cases where adequate and reliable 7-dependence studies of the electrode kinetics have been made (cf. Yeager ). Simple ionic redox reactions seem, however, to be an exception. ... 

Figure 4.15. General phenomenological retention model for a solute that participates in a secondary chemical equilibrium in reversed-phase chromatography. A = analyte, X = equilibrant, AX = analyte-equiUbrant complex, Ksce = secondary chemical equilibrium constant, and and Kax re the primary distribution constants for A and AX, respectively, between the mobile and stationary phases.

Thus, this interspace model has been cast in the form of the general phenomenological model of Section 2b (Eqns. 33 and 35), and the relevant parameters of coupled water transport may be calculated as outlined there. 

---