Structural inhomogeneity

The problem of taking into consideration the actual vacancy-mediated atomic exchange mechanism (rather than the direct exchange model used in most theoretical treatments) recently received some attention. In particular, possible presence of vacancy segregation at various structural inhomogeneities was discussed. However, the estimates of these effects by various authors disagree notably with each other , and there seems to be no general treatment of this problem available. 

The porosity and permeability of CP are the most important factors determining their ability to sorb and immobilize BAS. For solving these problems, it was necessary to synthesize various types of porous and permeable CP differing in the mobility of elements of the crosslinked structure and in the rigidity of the polymer backbone. For biological problems related to the application of CP as biosorbents, it has been found necessary to use CP with a marked structural inhomogeneity. 

Hecht, A-M Duplessix, R Geissler, E, Structural Inhomogeneities in the Range 2.5-2000 Angstroms in Polyacrylamide Gels, Macromolecules 18, 2167, 1985. 

A highly detailed picture of a reaction mechanism evolves in-situ studies. It is now known that the adsorption of molecules from the gas phase can seriously influence the reactivity of adsorbed species at oxide surfaces[24]. In-situ observation of adsorbed molecules on metal-oxide surfaces is a crucial issue in molecular-scale understanding of catalysis. The transport of adsorbed species often controls the rate of surface reactions. In practice the inherent compositional and structural inhomogeneity of oxide surfaces makes the problem of identifying the essential issues for their catalytic performance extremely difficult. In order to reduce the level of complexity, a common approach is to study model catalysts such as single crystal oxide surfaces and epitaxial oxide flat surfaces. 

We have to take into account these effects when the dyes are located in structurally inhomogeneous environments, for instance, in the core and on the surface of a nanoparticle. If their core is low-polar and the surface is exposed to an aqueous solvent, we will observe that the energy flow is directed to the dyes located at the surface. It is because their absorption and emission spectra are shifted to the red due to the fact that they are more efficient as FRET acceptors. 

Thus, at present, fluorescence spectroscopy is capable of providing direct information on molecular dynamics on the nanosecond time scale and can estimate the results of dynamics occurring beyond this range. The present-day multiparametric fluorescence experiment gives new opportunities for interpretation of these data and construction of improved dynamic models. A further development of the theory which would provide an improved description of the dynamics in quantitative terms with allowance for the structural inhomogeneity of protein molecules and the hierarchy of their internal motions is required. 

Earlier, the same conclusion was made by Dusek et al. 92>, who believed that the systems under study did not exhibit any special features characteristic of structural inhomogeneities and that their structure does not differ essentially from that observed in the glassy linear polymers. However, a feature that is typical of just the epoxyamine polymers may exist it is connected with the autocatalytic formation of epoxyamine polymers. 

In electrode kinetics, interface reactions have been extensively modeled by electrochemists [K.J. Vetter (1967)]. Adsorption, chemisorption, dissociation, electron transfer, and tunneling may all be rate determining steps. At crystal/crystal interfaces, one expects the kinetic parameters of these steps to depend on the energy levels of the electrons (Fig. 7-4) and the particular conformation of the interface, and thus on the crystal s relative orientation. It follows then that a polycrystalline, that is, a (structurally) inhomogeneous thin film, cannot be characterized by a single rate law. 

Scission of chemical bonds results from the concentration of mechanical energy of the structural inhomogeneities this represents mechanocracking or mechanochemical destruction. 

Width of the transition. The a transitions are generally considerably sharper than secondary ones. The width of the a transition can be related to the degree of inhomogeneity of the spatial distribution of crosslink density (see Sec. 10.3.4). In contrast, secondary transitions can be considered intrinsically broad their width cannot be related to structural inhomogeneities. 

In the case of a structurally inhomogeneous series of antihistamines, the sedative side-effects were found to be much better described by their octanol-water distribution coefficient at pH 7.4, log D, than by Alog P0ct.-aik. or their hydration capacity, Aalkane [b7[. 

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