Plateau regime

Figure 14 Master curve generated from mean-square displacements at different temperatures, plotting them against the diffusion coefficient at that temperature times time. Shown are only the envelopes of this procedure for the monomer displacement in the bead-spring model and for the atom displacement in a binary Lennard-Jones mixture. Also indicated are the long-time Fickian diffusion limit, the Rouse-like subdiffusive regime for the bead-spring model ( ° 63), the MCT von Schweidler description of the plateau regime, and typical length scales R2 and R2e of the bead-spring model.

Fig. 1.2 Richness of dynamic modulus in a bulk polymer and its molecular origin. The associated length scales vary from the typical bond length ( A) at low temperatures to interchain distances ( 10 A) around the glass transition. In the plateau regime of the modulus typical scales involve distances between entanglements of the order of 50-100 A. In the flow regime the relevant length scale is determined by the proper chain dimensions...

At potentials near the photocurrent onset (roughly Fn,), a spiked response is seen with a characteristic overshoot when the light is turned off. At positive potentials near the plateau regime (again for the specific illustrative case of an n-type semiconductor), the response reverts to a rectangular profile that mimics the excitation waveform. Intermediate response patterns manifest at potentials in between. 

Equation (1.105) can be used to obtain a criterion on the path length required to sample all important pathways. According to the reasoning of the preceding sections, pathways are sufficiently long if the time derivative dC t)/dt reaches a plateau. But dC t)/dt can reach a plateau only if does so. In this plateau regime, the first derivative of ... 

The local mobility of DNA in these arrays exhibits a peculiar dependence on molecular weight and electric field, as seen in Figure 54.14. At weak electric fields, the shorter DNA are more mobile. In contrast, there exists a plateau regime at higher electric fields where the longer DNA moves more quickly. The plateau region is of particular interest for applications, since it would allow rapid separations. 

Built-up multilayers can be obtained only for transfer achieved at a surface far beyond the plateau regime, generally around 35 mN/m. Hence the resulting films are just a disordered superposition of oken monocrystals, with a random orientation in the plane of the support, as shown in Fig. 2b. As a consequence, the normal to the support behaves as an axis of full rotation. Such a macroscopic configuration is easy to investigate. This was done by the use of two different resonance methods, namely, linear dichroism and electron spin resonance, with the following result TCNQ radical anions lie completely flat on the substrate in the dimeric form [9]. Obviously, such a structure is not compatible with an in-plane conductivity, for which TCNQ molecular planes should be perpendicular to the substrate. In addition, the complete charge transfer between pyridinium and TCNQ prevents any kind of electron conductivity in the film and, as expected, the electrical properties of the pristine film are those of an insulator. 

The only data for MgO appear to be for isovalent Ni additions [204]. The hardening rate at ambient temperature is somewhat higher than that for Ti + in sapphire, and the data best fit a c law. The plateau regime begins at about 400 °C for MgO (at least for Fe additions [205]), and so the yield stress behavior is in the low-temperature region where the solution-hardening rate is temperature-dependent. 

We consider now the case when the surface is saturated with isotropic blobs from long chains. As discussed previously, this may be realized even when the bulk concentration in probe chains is very sm l. In the plateau regime, the surface is covered... 

Last section dealt with the concentration profile of the adsorbed large polymers. We saw that in a dilute bulk solution and in the plateau regime, it extends to distances of the order of the radius of a chain. In a semi-dilute solution, we expect the same profile to be... 

For the total electrical conductivity obtained by the four-probes technique, a narrow plateau regime due to ionic conduction and a slope of approximately —1/6 due to n-type conduction were observed imder high and low partial oxygen pressure regions, respectively. The total electrical conductivity was then fitted by the following equation ... 

---