Quasi-variational formalism

First we apply the formalism to the short-term 14C variations. If we assume that they are caused by quasi cyclic l4C production rate variations with a period of 200 y [42] we get a dilution factor... 

D.A. Micha, E. Brandas, Variational Methods in the Wave Operator Formalism. A Unified Treatment for Bound and Quasi-Bound Electronic and Molecular States, J. Chem. Phys. 55 (1971) 4792. 

The GMS wave function [1,2] combines the advantages of the MO and VB models, preserving the classical chemical structures, but dealing with self-consistently optimized orbitals. From a formal point of view, it is able to reproduce all VB or MO based variational electronic wave functions in its framework. Besides that, it can deal in a straightforward way with the nonadiabatic effects of degenerate or quasi-degenerate states, calculating their interaction and properties. 

Except for the efforts mentioned above, relativistic calculations of shielding evaluate the main relativistic effects using one or two component limits of the four-component formalism, quasi-relativistic approaches. These avoid the variational collapse in the calculation of the scalar relativistic terms by employing frozen cores, or effective core potentials. Some include the one-electron spin-orbit terms, and sometimes the higher order spin-orbit terms too. Others include both scalar and spin-orbit terms. Ziegler... 

This two-variable system (Goldbeter et al, 1978) presents the additional advantage of being formally identical with the system of eqns (2.7) studied in chapter 2 for glycolytic oscillations. This similarity stems from the basic structure common to the two models a substrate, injected at a constant rate, is transformed in a reaction catalysed by an allosteric enzyme activated by the reaction product. In the cAMP-synthesizing system in D. discoideum, activation is indirect as extracellular cAMP enhances the synthesis of intracellular cAMP, which is then transported into the extracellular medium. However, the hypothesis of a quasi-steady state for intracellular cAMP is tantamount to considering that the variation of )8 is so fast that the enzyme is, de facto, activated directly by its apparent product, extracellular cAMP. 

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