Polarization terms Links

Bodor and Brewster (1983) first used the term CDS, in describing the use of dihydropyridine ester- (or amide)-linked prodrugs such as 27 (X-OH is the parent) which can partition readily into the CNS, there to be oxidized to pyridinium salts (28), which are effectively trapped in the biophase because of their extreme polarity, and which then undergo enzymic or chemical hydrolysis of the now very labile ester link to release active drug. 

Classical anharmonic spring models with or without damping [9], and the corresponding quantum oscillator models seem well removed from the molecular problems of interest here. The quantum systems are frequently described in terms of coulombic or muffin tin potentials that are intrinsically anharmonic. We will demonstrate their correspondence after first discussing the quantum approach to the nonlinear polarizability problem. Since we are calculating the polarization of electrons in molecules in the presence of an external electric field, we will determine the polarized molecular wave functions expanded in the basis set of unperturbed molecular orbitals and, from them, the nonlinear polarizability. At the heart of this strategy is the assumption that perturbation theory is appropriate for treating these small effects (see below). This is appropriate if the polarized states differ in minor ways from the unpolarized states. The electric dipole operator defines the interaction between the electric field and the molecule. Because the polarization operator (eq lc) is proportional to the dipole operator, there is a direct link between perturbation theory corrections (stark effects) and electronic polarizability [6,11,12]. 

The long-term stability of the material is an essential aspect, particularly when a periodical polarity reversal is applied. Using metallic or nonstable materials which could be corroded (mainly under oxygen evolution conditions) induce undesired long-term pollutions in treated waters and moreover generate additional costs linked to frequent replacement of the electrodes. 

Here E, D, and P represent, respectively, the electric field, electric induction (or displacement), and electric polarization vectors P (D - )/4x. The integration must be carried out over all space penetrated by the electrostatic field. Equation (5.6.1), while correct, is awkward in several respects. First, there is the need to integrate over all space, including the region outside the system of interest. In the presence of a medium, the electric lines of force not only are present within the specimen, but also bulge out in all directions away from the system these effects must be included in (5.6.1). Second, there is a tendency in the literature to associate the first term in (5.6.1b) with the establishment of the electric field in free space, and the second term with the reaction of the medium to the electric field. This is wrong The quantity D is subject to direct experimental control because it is linked by Maxwell s equation to the presence of free charges by contrast, E is in part a reaction field that also includes the... 

Of particular interest are the intramolecularly ionic meropolymethine dyes (especially the merocyanines), whose electronic structure lies somewhere between that of polyenes and that of polymethines depending on the nature of X and X as well as on solvent polarity [20], These are systems in which an electron-donating group, D, is linked by a conjugated system, R, to an electron-accepting group, A. Their intermediate r-electronic structure can be described in terms of two mesomeric structures, D—R—A D —R—A , as, for example, this special vinylogous merocyanine dye ( = 0,1,2,...) ... 

---