Structural relaxation time coupling model

A model having predictions that are consistent with the aforementioned experimental facts is the Coupling Model (CM) [21-26]. Complex many-body relaxation is necessitated by intermolecular interactions and constraints. The effects of the latter on structural relaxation are the main thrust of the model. The dispersion of structural relaxation times is a consequence of this cooperative dynamics, a conclusion that follows from the presence of fast and slow molecules (or chain segments) interchanging their roles at times on the order of the structural relaxation time Ta [27-29]. The dispersion of the structural relaxation can usually be described by the Kohlrausch-William-Watts (KWW) [30,31] stretched exponential function,... 

For example, if the molecular structure of one or both members of the RP is unknown, the hyperfine coupling constants and -factors can be measured from the spectrum and used to characterize them, in a fashion similar to steady-state EPR. Sometimes there is a marked difference in spin relaxation times between two radicals, and this can be measured by collecting the time dependence of the CIDEP signal and fitting it to a kinetic model using modified Bloch equations [64]. 

The vibronic spectra of Do — Di — D2 electronic states recoded by da Silva Filho et al. [45] revealed resolved vibrational structures of the Do and D2 electronic states and a broad and structureless band for the Di state. A slow ( 3-20 ps) and fast k, 200 fs) relaxation components are estimated for the Dq D2 transition in a (femto)picosecond transient grating spectroscopy measurements [16]. The fast component is attributed to the Do D2 transition and a nonradiative relaxation time of 212 fs is also estimated from the cavity ringdown (CRD) spectroscopy data [42]. Electronic structure results of Hall et al. [107] suggest that the nonradiative Do D2 relaxation occurs via two consecutive sloped type CIs [66,108]. We developed a global model PESs for the Do — Di— D2 electronic states and devised a vibronic coupling model to study the nuclear dynamics underlying the complex vibronic spectrum and ultrafast excited state decay of N +[20]. 

One problem encountered with polymeric membranes is their physical aging which can alter the permeation and the mechanical properties. Sinko et al. [144] noticed a decrease in the water permeability and in the mechanical rate of relaxation with time, which was proportional to the aging temperature. A relaxation coupling model could be used to predict equilibrium in the structural change profile. 

The molecular model was generated using only NMR data based on the assignment of at least a major portion of all 59 residues." The cluster structure, moreover, was generated as part of the NMR structure. In addition to the conventional NOESY, NHC 3 spin coupling and H-bond (based on NH lability) constraints, the structure of the cluster and its environment benefited from the use of relaxation times [Eq. (1)] and the Cys Fe-S-Cp-H dihedral angle, < >, deduced fiom the contact shift pattern via Eq. (6), as well as short mixing time NOESY and steady-state NOEs, as structural constraints. The nature of the constraints... 

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