Physicochemical meaning

There are some subtleties with respect to the physicochemical meaning of the contact angle equation, and these are taken up in Section X-7. The preceding, however, serves to introduce the conventional definitions to permit discussion of the experimental observations. 

Most of the 2D QSAR methods are based on graph theoretic indices, which have been extensively studied by Randic [29] and Kier and Hall [30,31]. Although these structural indices represent different aspects of molecular structures, their physicochemical meaning is unclear. Successful applications of these topological indices combined with multiple linear regression (MLR) analysis are summarized in Ref. 31. On the other hand, parameters derived from various experiments through chemometric methods have also been used in the study of peptide QSAR, where partial least square (PLS) [32] analysis has been employed [33]. 

Equations (37)—(39), where the non-additivity of multiple substituent effects is described by a cross-term, express correctly the rate data for bromination and other reactions of polysubstituted substrates. The question arises, therefore has the interaction constant, q, any physicochemical meaning in terms of mechanism and transition state charge To reply to this question, selectivity relationships (42) that relate the p-variation to the reactivity change and not to any substituent constant, have been considered (Ruasse et al., 1984). 

The fearsome-looking word physicochemical means relating to physical chemistry. ... 

Some members of a receptor population are in the R state, even in the absence of any agonist. Thus, the receptor can be thought of having a tone like a resting muscle. The ratio of states is defined by the equilibrium constants Kp and (for drug D or inhibitor I), and gives true physicochemical meaning to the concept of intrinsic activity. 

The parachor does not have a readily apparent physicochemical meaning it is useful as a parameter for estimating a range of other properties, especially those related to liquid-liquid interactions. 

As fugacity can be considered, from the point of view of its physicochemical meaning, a tendency of the substance to escape from the given system and to pass over into another system, it actually expresses how many times this property of a substance in a given state is strengthened or weakened in comparison with the standard state. At a suitable choice of the standard states in individual cases and under the assumption of the ideal behavior of the sub-... 

However, Dubinin and co-workers do not accept the concept of monolayer formation in micropores and propose determining the microporous volume, Fq, on the basis of the thermodynamic theory of Polanyi adsorption. However, one can observe that the monolayer volume, Vm, when expressed in liquid nitrogen volume per unit mass, is very close to the Dubinin volume, Vo. The proportionality of the BET monolayer volume, Vm, and the so-called micropore volume, Va, (Vo 11 Vm) has been observed for many materials, as shown in different studies [2, 3]. This means that both variables are correlated, so determining one is equivalent to the determining the other. The discussion on the physicochemical meaning of these parameters may be interesting from a theoretical point of view but as far as practical characterization of porous materials is concerned, both methods can often be considered as equivalent. 

It has been thought (H38, H46, H47) that methods based on quantitation of the polysaccharide moiety of gastric mucin would be more specific for the assay of mucosubstances. This leads, however, to many difficulties as well, and is not acceptable if one does not subject the mucosubstances to prior fractionation by chemical or physicochemical means (see Section 2.4). 

The principal aims of this review are to indicate the role of chemisorbed intermediates in a number of well-known electrocatalytic reactions and how their behavior at electrode surfaces can be experimentally deduced by electrochemical and physicochemical means. Principally, the electrolytic gas evolution reactions will be covered thus, the extensive work on the important reaction of O2 reduction, which has been reviewed recently in other literature, will not be covered. Emphasis will be placed on methods for characterization of the adsorption behavior of the intermediates that are the kinetically involved species in the main pathway of the respective reactions, rather than strongly adsorbed by-products that may, in some cases, importantly inhibit the overall reaction. The latter species are, of course, also important as they can determine, in such cases, the rate of the overall reaction and its kinetic features, even though they are not directly involved in product formation. 

The same consideration is valid for the assumption of the conventional n-th order dependency of loss in crystallinity on normalized steam concentration. The relatively high value n=5.76 of the estimated exponent may have no physicochemical meaning due to the simplify-... 

It is difficult to give a physicochemical meaning to AE within the framework of an action mechanism. AE is the equilibrium energy difference between the most stable "boat" and "chair" conformer states. However, suppose the production of the ultimate carcinogenic metabolite depends upon two parallel metabolic reactions as depicted in Fig. 5a. The concentration,... 

Descriptors with clear physicochemical meaning and in common use among medicinal chemists should be used. 

Molecular descriptors are usually classified into several classes by a mixed taxonomy based on different points of view. For example, descriptors are often distinguished by their physicochemical meaning such as electronic descriptors, —> steric descriptors, —> lipophilicity descriptors,... 

If the fit caimot be achieved in a satisfactory form, the other models, which have been introduced in Sect. 4.1.2, should be tested with increasing complexity. In the worst case, spline models can be used, which, however, have no physicochemical meaning anymore. 

In contrast to general recommendations on the selection of biologically meaningful parameters [307], the physicochemical meaning of the topological parameters is never clear. 

---