Characteristic correlation time

We shall see that a conditional acceleration model in the form of (6.48) is equivalent to a stochastic Lagrangian model for the velocity fluctuations whose characteristic correlation time is proportional to e/k. As discussed below, this implies that the scalar flux (u,

joint velocity, composition PDF level, and thus that a consistent scalar-flux transport equation can be derived from the PDF transport equation. 

In Table 1, S2 is the general order parameter describing bond motions at the ps-ns time scale, te is the characteristic correlation time for these motions and Rex is the conformational exchange term representing motions on the ps-ms time scale. Internal motions on the ps-ns time scale are considered as the superposition of fast and slow motions characterized by S2 and if as well as Ss2 and ts. Here, S2 = Ss2Sf2 and t, [Pg.52]

Native GPI-anchored proteins diffuse more rapidly in supported lipid bilayers than transmembrane proteins, presumably because the lipid tail of the GPI anchor does not extend completely through the lipid bilayer [111]. To investigate the relationship of GPI-anchor structure to the mobility on the membrane, the glycan core of GPI anchor was substituted with no (87), one (88) or two mannosyl units (89). These GPI anchored protein analogues were incorporated into supported lipid bilayers. The diffusion properties of GFP-2, GFP-3 and GFP-4 in supported lipid bilayers were investigated by FCS. From these FCS measurements, the characteristic correlation times (td) and the diffusion coefficient (D), a physical measure of protein mobility, were obtained. GFP-4, which contains two monosaccharides in... 

In a more realistic model, which takes into account the fact that the chain conformation can deviate from the strict tetrahedral geometry, the anisotropy r t) acquires a more complex form (it contains two characteristic correlation times) [98]... 

A characteristic correlation time of the intensity fluctuation obtained by time correlation function analysis was about 150 min. In the case of the cubic lattice from a lamellar phase the... 

In the case of liquid lattices, the difficulty in adequately characterizing their structures renders them unsuitable for treatment by quantum mechanics. Accordingly, liquid lattices are often treated classically by considering the effects of molecular rotations and translations, with characteristic correlation times, r, on time-dependent magnetic and electric fields that may influence relaxation processes. Accordingly, it becomes convenient to depart from the phonon description of sound and adopt a classical view of this as the sinusoidal propagation of a pressure wave through a medium. 

It is clear from a variety of spectroscopic techniques that biomembranes are dynamic not static structures. It is also known that certain membrane functions depend critically on the fluidity of the membrane lipids. Spin-labelled and fluorescent-labelled lipid probes are found to perform rotational motions in the nanosecond timescale in fluid lipid bilayers and membranes. For diffusive rotation the characteristic correlation times are given by the Debye equation (t = n V/kT) and correspond to effective viscosities in the range q 0.1-1 poise. A spin-labelled steroid analogue of cholesterol for instance rotates rapidly about its long... 

In order to construct a scaling theory of polymer dynamics one needs to know, as an input, the variation of the characteristic correlation time T under rescaling of the length unit. This defines a dynamic exponent z such that... 

In another report, the solvation micro-dynamics in 4-methyl-IV-butyl-pyridinium tetrafluoroborate, [4-mebupy][BF4], was studied by F-NMR and EPR spectroscopy using Gd(iii)(OTf33 as a probe.The electron spin-spin relaxation time Tae of the paramagnetic Gd(iii) ion was calculated from the EPR line width and found to be 31 ps at 293 K with an activation energy of 12.9 0.8 kj mol. Combining both temperature-dependent NMR and EPR results it was concluded that, at low temperatures the characteristic correlation time of the F relaxation is the electron spin-spin relaxation of Gd(iii), whereas at high temperature the correlation time is dominated by the chemical exchange of the Gd(in) solvation complex. 

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