Molecular motion, high amplitude

A common feature observed was the departure between the steady shear viscosity ( 7a) and the real component of the dynamic viscosity (/ ) at large values of shear rate and frequency, with the expected more rapidly decrease of t] with frequency than rja does with shear rate (Bird et al., 1977a), which can be attributed to the very different molecular motions involved in the dynamic and steady shear at high m and y (Ferry, 1980). Because of the relatively high value of strain amplitude used in our tests (36%) and the two-phase nature of our HM dispersions, the observations with respect tor) and t)a are in agreement with those of Matsumoto et al. (1975). 

Thermodynamics and motion can be used as a base for an operational definition of the solid state. A solid is a phase below its glass- or melting-transition temperature where the molecular motion is almost completely restricted to small-amplitude vibrations. Both transitions are easily determined by thermal analysis (the operation). Recently it has become possible by simulation on supercomputers to establish the link from the microscopic thermal motion of macromolecules to the macroscopic thermal analysis. By solving the equation of motion, one can produce a detailed movie of molecular motion (see Sect 1.3.4, Fig. 1.47). At high temperature, conformational disorder is seen, i.e., the crystal can change to a condis state. Note that even the conformational motion occurs in a picosecond time scale (see Sect. 5.3.4). 

Saturation transfer is a technique that is sensitive to very slow motions with correlation times from 10 to 10 s—a region where conventional ESR is not sensitive [89]. It has been used extensively in spin label studies of biological systems [90], [91]. Spectra are recorded under saturation conditions and high modulation amplitudes, as second harmonic in-phase and quadrature spectra. The method measures the transfer of saturation throughout a spectrum by reorientational molecular motions. The line shape is sensitive to molecular motions and the saturation properties of the spin label. 

Although at low shear rates and low frequencies, respectively, the non-Newtonian viscosity v and the dynamic viscosity rf reflect similar characteristic times, it would not be expected that and j/(-y) should be similar functions at large values of their respective arguments, since steady flow at a high shear rate involves very different molecular motions from oscillating flow at low amplitudes where escape from topological restraints is not required. However, it has been frequently observed that 1j7 ( ) closely resembles v y). Here j (< )) = = (7 /(d,... 

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