Configurational fluctuations

The radial distance distribution in simple atomic and molecular fluids is determined essentially by the exclusion volume of the particles. Zemike and Prins [12] have used this fact to construct a one-dimensional fluid model and calculated its radial distance correlation function and its scattering function. The only interaction between the particles is given by their exclusion volume (which is, of course, an exclusion length in the one-dimensional case) making the particles impenetrable. The statistical properties of these one-dimensional fluids are completely determined by their free volume fraction which facilitates the configurational fluctuations. 

Figure 8.2 Stretching vector of a chain segment. The schematic illustration shows that configurational fluctuations pervade a large volume...

It has often been assumed that the second step, intracomplex ET, takes place within a static reactant complex. However, a number of cases have been observed in which the reactant complex is not static, but undergoes dynamic configurational fluctuations (defined as protein-protein orientations in the bound complex) [65] or conformational changes (defined as a tertiary structure of each protein) [40]. If the reaction is rate limited by dynamic fluctuation in configuration rather than by the... 

In situ STM of metalloproteins with localized low-lying redox levels can be expected to follow ET patterns similar to metalloprotein ET in homogeneous solution and at electrochemical surfaces. The redox level is thus strongly coupled to the protein and solvent environment. A key notion is that the vacant local level (oxidized form) at equilibrium with the environmental nuclear motion is located well above the Fermi levels of both the substrate and tip, whereas, the occupied level (reduced form) at equilibrium is located well below the Fermi levels. Another central notion is that the local redox level at the transition metal centre is still much lower than environmental protein or solvent electronic levels. The redox level therefore constitutes a pronounced indentation in the tunnel barrier. This alone would strongly enhance tunnelling. Configurational fluctuations in the environment can, secondly take the redox level to such low values that temporary physical population occurs. This requires nuclear activation but can still be favourable due to the much shorter electron tunnel distances... 

If a liquid is reversibly cooled below the melting point, the solid, i.e., a three-dimensional giant molecule ( 3D polymer ) forms, characterized by a long range order. So-formed crystals exhibit strict periodicity. While, in the case of liquids, structural configurations fluctuate in space and time, glasses as frozen liquids or other amorphous solids show also fluctuations but essentially only with respect to the position coordinate. 

It was found [41] that 90% of the total configurational fluctuations can well be represented in terms of about 10 principal components at each temperature. 

At T = 0.2-0.4, most of the system fluctuations are approximately localized on a few PCs for both the models. As the temperature increases, the system fluctuations become more delocalized, spreading over a wider range of the PCs. Note, however, that the number of the PCs required to represent the total configurational fluctuation of the systems are largest about their transition temperatures, T = 0.72 (BLN) and T = 0.6 (Go-like). 

Thus we see that as in the case of rods, the coil must be large enough so that its configurational fluctuations can be seen by the light wave in order for configurational dynamic constants to affect the scattered field time-correlation function. 

Chu and co-workers (IJO, 111) have studied the photon correlation function of light scattered by solutions of narrow molecular weight fractions of PS (Mn = 397,000) in cyclohexane near the critical demixing temperature Tc- Their data fit Equations 82 and 83 with y = 1.26 0.08, y = 0.77. The correlation lengths were in the range of 100-250A, and Vs = 0.62, vr = 0.58. For (T — Tc) < 0.1°, deviations from the critical exponent concept were discovered which may result from macro-molecular polydispersity or configurational fluctuations 111)-... 

The gallide YbCuGa (Adroja et al. 1990, Malik et al. 1987a,b) shows a susceptibility behavior typical for an intermediate-valent compound (fig. 13). This behavior can be understood in terms of the ionic-configuration-fluctuation (ICF) model (Sales and Wohlleben 1975). A fit according to this model results in a temperature-independent... 

We will discuss if the size exponents (i/ or ve) are affected by the lattice (configurational) fluctuations if r (p) is different from i/ or if i/ is different from i/J for p < 1. This question arises naturally from the application of the Harris criterion [8] to the n-vector model in the n —> 0 limit [2], when the partition function graphs are all SAWs. A naive application of the criterion to the SAWs suggested [6] a possible disorder induced crossover in the critical behaviour of SAW statistics for any amount of disorder (p < 1). A modified... 

Hur JS, Shaqfeh ESG, Babcock HB, Chu S (2002) Dynamics and Configurational Fluctuations of single DNA Molecules in Linear Mixed Hows. Phys Rev E 66(011915)... 

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