Cooperativity dynamic

Glassy Systems A Probe for Cooperative Dynamical Length Scales. 

Eolmer BJB, Sijbesma RP, Kooijman H, Spek AL, Meijer EW. Cooperative dynamics in duplexes of stacked hydrogen-bonded moieties. J Am Chem Soc 1999 121 9001-9007. 

This remark may have relevance to the cooperative dynamics of protein assemblies. 

In this work we perform an investigation of cooperative static in the monoclinic phase and dynamic in rhombohedral JT effect of pure LaMn03 using pair interionic potentials in shell model approximation with the direct inclusion of the JT term in crystal energy and dynamic matrix of a crystal. The magnetic and RS properties of the rhombohedral LaMn03 are simulated in the framework of the cooperative dynamical effect approximation. 

The assumption of cooperative dynamical JT effect in rhombohedral LaMn03 can... 

The temperature of transition is small relative to the value of splitting of the Mn3+ 5E ground state. That is why we suppose that the transition from monoclinic to rhombohedral phase is a transition from static to dynamic JT effect. Because of the strong correlation in motion of different [Mn06] octahedra we suppose that there is a cooperative dynamical effect. 

In the framework of approximation of cooperative dynamical effect, the appearance of a new high frequency RS line in rhombohedral LaMn03 can be explained. 

As a result of averaging of orbital structure angle due to cooperative dynamical effect, the FM interactions just due to superexchange can appear in rhombohedral manganites. 

V. Cooperative Dynamic and Scaling Phenomena in Disordered Systems... 

Non-Debye dielectric relaxation in porous systems is another example of the dynamic behavior of complex systems on the mesoscale. The dielectric properties of various complex multiphase systems (borosilicate porous glasses [153-156], sol-gel glasses [157,158], zeolites [159], and porous silicon [160,161]) were studied and analyzed recently in terms of cooperative dynamics. The dielectric response in porous systems will be considered here in detail using two quite different types of materials, namely, porous glasses and porous silicon. 

Therefore, the observed process (I) could be related to the cooperative dynamics of glycerol in the supercooled phase, while process (II) is most likely related to the crystalline phase of glycerol and is the result, similar to water, of the mobility of defects in the crystalline lattice [200]. The temperature dependence of the relaxation time for dehydrated glycerol is compared in Fig. 23 with those for the usual behavior of glycerol, which has absorbed some water from the atmosphere. 

V. COOPERATIVE DYNAMIC AND SCALING PHENOMENA IN DISORDERED SYSTEMS... 

In this context, the value To should be associated with the smallest cooperative relaxation time reflecting the EW dynamics obeying the same VFT temperature law as the main relaxation times x and xmax (see Fig. 26). At the same time, the ratio x/xo is strongly dependent on concentration (Fig. 38). The increase of the ratio x/xo with increase of water content indicates that the EW of glycerol is eroded by water molecules much faster than the main relaxation process. In order to clarify such a mechanism, let us assume that the EW is the result of some fast short-range cooperative dynamics that can be associated with... 

Besides the bilayer type dynamic interfaces there also exist dynamic interfaces involving SAMs. The cooperative dynamic nature of SAMs on gold has been confirmed previously [107], On 2D surfaces the level of mobility in gold-thiol SAMs has been looked at and is considered quite slow ranging from 10 18 to 10 14 cm2 s 1 ( 1 nm/h) [109,108] when compared to phospholipid and membrane protein, lateral mobilities of around 10 8 cm2 s... 

Static H Multiple Quantum (MQ) NMR spectroscopy, on the other hand, has shown the ability to more reliably quantitatively characterize elastomer network structure and heterogeneities (14-19). H MQ NMR methods allow for the measurement of absolute residual dipolar couplings (magnetic susceptibility and field gradients which complicate relaxation measurements (13, 14, 20,21). It has previously been shown that the residual dipolar couplings are directly related to the dynamic order parameter, Sb, and the crosslink density (1/N)(P) ... 

Fig. 15. (a) Normalized pure-exchange CODEX intensities E(tm) as a function of tm for the aromatic ternary CH and the quaternary Cquat in Td-G2(-Me),6 dendrimer (T=363K). The fit curve for the ternary carbons is a stretched exponential cxp[—(rln/rcyi with /I = 0.51 and tc = 401 ms. The dotted line indicates the final CODEX exchange intensities, (b) Motional model of the localized, cooperative dynamics in polyphenylene dendrimers, including two-site jumps of all phenyl substituents of a pentaphenyl benzene building block. As indicated by X-ray analysis and computer simulations, the peripheral aromatic rings are inclined by 30° with respect to an axis normal to the face of the central benzene ring. For details, see ref. 44. 

Nanoscale Solvation Theory of Folding Cooperativity Dynamic Benchmarks and Constant of Motion... 

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,... 

The fractional exponent KWW can be rewritten as (1 — n), where n is the coupling parameter of the CM. The breadth of the dispersion is reflected in the magnitude of n and increases with the strength of the intermolecular constraints. The dispersion and the structural relaxation time are simultaneous consequences of the many-molecule dynamics, and hence they are related to each other. The intermolecularly cooperative dynamics are built upon the local independent (primitive) relaxation, and thus a relation between the primitive relaxation time To and Ta is expected to exist. The CM does not solve the many-body relaxation problem but uses a physical principle to derive a relation between Ta and To that involves the dispersion parameter, n. This defining relation of the CM... 

An alternative explanation is based on the dispersion and its dependence on the dynamic variables probed (i.e., rotation versus translation) [172]. The dispersion of rotational diffusion and of the shear viscoelastic response is broader than that of translational diffusion or the mean-square displacement of the molecule. It is a consequence of the cooperative dynamics that the dispersion of different dynamic variables for the same substance can be different and the... 

---