Dynamically correlated domains

Similar heterogeneous model has been used to develop a relaxation function by Chamberlin and Kingsbury (1994), who consider the localized normal modes to be involved in the relaxation process. Localized (domains) regions are assumed to be present between Tg and T. They are described as dynamically correlated domains (DCD). A Gaussian distribution of the domain sizes has been assumed, with each domain characterized by a Debye relaxation time. Expressions for the dielectric susceptibility have been derived and used to fit the experimental susceptibilities of salol, glycerol and many other substances with remarkable agreement over 13 decades of frequency (even when only one adjustable parameter is employed). 

Although these NMR data clearly support a dynamical model for disorder in P-cristobalite, they are not sensitive to whether the motions of adjacent oxygens are correlated (as required for a model of re-orienting twin domains), or, whether the motion is continuous or a hopping between discrete positions they indicate only that the path of each oxygen traces a pattern with 3-fold or higher symmetry over times of the order 4.7-10 s. Thus, these results cannot discriminate between models based on RUMs or dynamical twin domains, and place only a lower limit on the timescale of the motions. A tighter restriction... 

Despite numerous efforts, the dynamic properties of semidilute polymer solutions in organic solvents at T < 0 are poorly understood. To our knowledge, only one DLS experiment has been performed so far in the poor solvent domain of supercritical polymer solutions [4]. The most important issue which is yet to be resolved is whether the viscosity of the solvent or that of the solution should be used to calculate the dynamic correlation length from the Stokes-Einstein Eq.l2 [31]. 

Molecular dynamics simulations were employed to explore the dynamic heterogeneity in water motion around a protein-DNA complex. The complex chosen was the DNA-binding domain of human TRFl protein and a telomeric DNA (see Figure 11.1). It was observed that the slow water dynamics correlated with the relaxation time of HBs of the water molecules connected with the protein and the DNA. The restricted motion of such water molecules led to sluggish rotational and translational dynamics of the hydration layer near the protein and DNA molecules in their complexed forms as well as in their free forms (see Figure 11.2). 

We have studied a kinetic theory approach to the calculation of dynamical correlations in a dense fluid. By considering density correlations in phase space one can discuss the dynamics in terms of renormalized molecular interactions that take into account the existence of structural correlations in the fluid. The advantage of this approach is that through the properties of a single function, the phase space memory function, one can treat in a unified manner a variety of correlation functions without restriction to either wavelength-frequency domain or fluid density. 

With the aim of elucidating molecular dynamics in a small domain, we have constmcted several microspectroscopic systems, that is, (i) the confocal microscope with the excitation light source being a femtosecond NIR laser emitting a 35 fs pulse, and (ii) the fluorescence correlation spectroscopic system with optical tweezers. 

In an NMR analysis of the effects of /-irradiation induced degradation on a specific polyurethane (PU) elastomer system, Maxwell and co-workers [87] used a combination of both H and 13C NMR techniques, and correlated these with mechanical properties derived from dynamic mechanical analysis (DMA). 1H NMR was used to determine spin-echo decay curves for three samples, which consisted of a control and two samples exposed to different levels of /-irradiation in air. These results were deconvoluted into three T2 components that represented T2 values which could be attributed to an interfacial domain between hard and soft segments of the PU, the PU soft segment, and the sol... 

The estimated correlation times for the loop domains of the order of 10 4 s are obtained for the suppressed peaks in the [l-13C]amino-acid-labelled bR, including Gly, Ala, and Leu residues as shown in Figure 24C. The loop dynamics can be also examined by measurements of the 13C-1H dipolar couplings by DIPSHIFT experiment in which fluctuations of the Co,-Cp vector result in additional motional averaging as order parameters, in addition to the rotation of Ala methyl groups which scales the dipolar... 

Crosslinked polymer networks formed from multifunctional acrylates are completely insoluble. Consequently, solid-state nuclear magnetic resonance (NMR) spectroscopy becomes an attractive method to determine the degree of crosslinking of such polymers (1-4). Solid-state NMR spectroscopy has been used to study the homopolymerization kinetics of various diacrylates and to distinguish between constrained and unconstrained, or unreacted double bonds in polymers (5,6). Solid-state NMR techniques can also be used to determine the domain sizes of different polymer phases and to determine the presence of microgels within a poly multiacrylate sample (7). The results of solid-state NMR experiments have also been correlated to dynamic mechanical analysis measurements of the glass transition (1,8,9) of various polydiacrylates. 

At the mesoscopic scale, interactions between molecular components in membranes and catalyst layers control the self-organization into nanophase-segregated media, structural correlations, and adhesion properties of phase domains. Such complex processes can be studied by various theoretical tools and simulation techniques (e.g., by coarse-grained molecular dynamics simulations). Complex morphologies of the emerging media can be related to effective physicochemical properties that characterize transport and reaction at the macroscopic scale, using concepts from the theory of random heterogeneous media and percolation theory. 

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