Physicochemical approaches

Kerns, E. H., Di, L. Physicochemical profiling overview of the screens. Drug Discov. Today Technol. 2004, 1, 343-348. Van de Waterbeemd, H. Physicochemical approaches to drug absorption. In Drug Eioavailability (Methods and Principles in Medicinal Chemistry), Van de Waterbeemd, H., Lennernas, H., Artursson, P. (eds.), Wiley-VGH, Weinheim, 2003, pp. 3-20. 

As an example of suspected endocrine disruptors (EDs), studies of the estrogenic action of bisphenol A (BPA) have been in progress in medical, physiological, and biological fields. In this situation, physicochemical approaches are required to get the structural information of BPA trapped in biomembranes. Most recently, we have determined the site and the orientation of BPA trapped in phospholipid vesicles by NMR, using the HCS rule [47]. In particular, we have succeeded in monitoring the NMR spectral changes of phospholipid vesicles, which are induced by the BPA delivery. 

The models predicted by Tai and coworkers [213] allow one to simulate the functions of modified Ni catalysts and to propose ways to improve the e.d. ability of the catalyst, without claiming to imply a real mechanism. Full understanding of modified Ni will require further significant advances in the physicochemical approach. 

Blanshard, J. M. V. (1987). Starch granule structure and function A physicochemical approach. In "Starch Properties and Potential" (T. Galliard, ed.), pp. 16-54. John Wiley and Sons, Chichester. 

Liger-Belair, G. (2002). Physicochemical approach to the effervescence in Champagne wines. 

Clearly, in the framework of the proposed physicochemical approach, it is impossible to theoretically predict the values of chemical constants k0 for each particular reaction couple A-B. This drawback is known to be characteristic of any phenomenological consideration. Therefore, the inverse task is exercised in practice, namely, experimentally determined kinetic dependences x - t and y - t are used to calculate appropriate constants. 

It is clear that in general the kinetic dependences considered in this chapter gradually transform into each other with passing time. In contrast to the diffusional theory, the physicochemical approach thus gives a more complicated, not simply parabolic, relationship between the thickness of two chemical compound layers and the time, in accordance with the available experimental data in binary systems. 

Consider the growth process of the NiBi and NiBi3 intermetallic layers between nickel and bismuth in more detail to explain the difference in diffusional and physicochemical approaches to the same problem of the apparent absence of a chemical compound layer. From a physicochemical... 

In some experimental works, the simultaneous presence of multiple compound layers was observed. Therefore, just as in the framework of diffusional considerations it is necessary to explain why the number of compound layers is in most cases so small, so in the framework of the physicochemical approach proposed it is necessary to explain why in certain cases the number of those layers is so large. There are a few reasons for the formation of multilayered structures at the A-B interface. These may be summarised as follows. 

It should be emphasised, however, that Wagner s theory is quite inapplicable in the region of linear growth of chemical compound layers. By contrast, the physicochemical approach makes it possible not only to qualitatively explain the existence of linear growth region but in certain cases allows precise quantitative calculations of the ratio of the growth rates for the same layer in different reaction couples of the A-B multiphase system to be carried out. 

The ratio of the rates of diffusional (parabolic) growth of the same compound layer in different reaction couples can be predicted precisely knowing only the stoichiometry of all the compounds of a multiphase binary system. In this case, the Wagner and physicochemical approaches yield identical results which are in good agreement with the available experimental data. 

The physicochemical approach allows also certain exact predictions regarding the layer-growth rate in the linear region to be made, whereas in the framework of the Wagner approach the linear growth cannot be explained even qualitatively. 

Nevertheless, in this book the number of the theoretically substantiated kinetic equations, for the experimentalist to use in practice, appears to exceed that resulting from purely diffusional considerations. Whether the experimentalist will be pleased with such an abundance of equations is a wholly different question. Still, for many researchers in the field it is so tempting to employ the only parabolic relation and then to discuss in detail the reasons for (unavoidable and predictable) deviations from its course. Note that unlike diffusional considerations where each interface is assumed to move according to the square root of the time, in the framework of the physicochemical approach the layer-growth kinetics are not predetermined by any additional assumptions, except basic ones, but immediately follow in a natural way from the proposed mechanism of the reaction-diffusion process. 

In spite of their seeming variety, theoretical approaches of different authors to the consideration of solid-state heterogeneous kinetics can be divided into two distinct groups. The first group takes account of both the step of diffusional transport of reacting particles (atoms, ions or, in exceptional cases if at all, radicals) across the bulk of a growing layer to the reaction site (a phase interface) and the step of subsequent chemical transformations with the participation of these diffusing particles and the surface atoms (ions) of the other component (or molecules of the other chemical compound of a binary multiphase system). This is the physicochemical approach, the main concepts and consequences of which were presented in the most consistent form in the works by V.I. Arkharov.1,46,47... 

W. Norde and J. Lyklema, Protein adsorption and bacterial adhesion to solid surfaces a physicochemical approach, Colloids Surf. 38, 1-13 (1989). 

Recent studies demonstrate that the thermophysical properties of textiles may be improved or even optimized. Such studies offer a variety of physical, chemical, and physicochemical approaches for conducting further research on the thermal characteristics of textiles that can be applied toward energy conservation. 

In the latter half of this century physicochemical approaches have increasingly become spectroscopic ones. Infrared (IR), Raman, and nuclear magnetic resonance (NMR) spectroscopic approaches can be used to register spectra characteristic of the... 

The physicochemical approach to retention time prediction has the advantage of accounting for the pH of the system by explicitly calculating p/C values... 

It is clear from the above discussion that the rheological properties of FCOJ will depend on the °Brix, pulp content, size and shape of the pulp particles, and pectin content of FCOJ sample, and the temperature at which the data were obtained. Carter and Buslig (1977) studied particle size distribution in commercial frozen FCOJ samples. Mizrahi and coworkers conducted systematic studies on FCOJ that they described as a physicochemical approach (Mizrahi and Berk, 1970 Mizrahi and Firstenberg, 1975 Mizrahi, 1979). They used a modified Casson equation to describe the flow behavior of FCOJ. 

Mizrahi, S. 1979. A review of the physicochemical approach to the analysis of the structural viscosity of fluid food products.. 7. TextureStud. 10 67-82. 

A Common Physicochemical Approach and Specificity of Scientific Problems... 

Today, the research of construction materials involves transition from the phenomenological to the physicochemical approach, i.e. to the study of the molecular mechanisms of degradation processes using methods of the physics and physicochemistry of polymers. The practical result of these investigations will be scientifically sub-... 

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