Intermediate timescale

In the intermediate timescale of interventions, where the width of Ff co) is broader than the width (so that the GR is violated) but narrower than the width of G co) (so that the QZE does not hold), the overlap of Ff co) and G a>) grows as the rate of interruptions, or modulations, increases. This brings about the increase of relaxation rates R t) with the rate of interruptions, marking the anti-Zeno effect (AZE) [13,45, 67] (Eigure4.4b). Qn such timescales, more frequent interventions... 

There are also tremendous possibilities for using RDCs as a direct probe of conformational dynamics. Recalcitrant problems such as the characterization of intermediate timescale motions (microsecond-nanosecond), both for... 

As future direction, and the fact that mass spectrometry has evolved very rapidly in the last decade, other mass spectrometry based technologies such as ion mobility (Thalassinos et al., 2004 Clemmer et al., 2005) may play an important role in the screening of reactive metabolites. This separation stage is orthogonal to the LC and mass spectrometric separations and occurs on an intermediate timescale... 

NMR is ideally suited to explore molecular motions in the polymer. Different types of motion can be discriminated on behalf of their timescale and geometry of exchange. One-dimensional quadrupole echo lineshapes (see Section 6.2.7.1) are particularly sensitive to segmental dynamics [1-6, 9-12], when there is either fast exchange between discrete geometries (with Tc <1/Avq) or when the motion occurs on the intermediate timescale (tc= 1/Aj q). Dynamic processes in the intermediate to slow motional limit (tc > l/Ar Q) are addressed by 2D exchange spectroscopy (see Section... 

Any motion on the fast or intermediate timescale changes the appearance of the static powder spectrum, as shown in Fig. 6.2.2 on the left. When the orientation of the C—bond gets rapidly averaged around a symmetry axis (with Tc I/Aj q), the spectrum retains its axially symmetric powder lineshape but its width is narrowed by a geometric factor. Given that 8 is the new effective angle between the motional symmetry axis and Bq, Equation... 

The previous section has been concerned with a NMR lineshape analysis of motional effects, which is most informative on the intermediate timescale. Any dynamics in the very fast or ultraslow correlation time limit, however. 

It might be expected that the Hugoniots calculated with this method and experimental measurements made on the same timescale would be in agreement. This timescale correspondence is a very loose criterion and the quality of agreement between simulations and experiments on timescales before the final thermodynamic state is reached likely depends on details of the partieular material system. Some qualitative agreement between simulations and experiments on intermediate timescales is demonstrated for silicon in a later section of this chapter. Simulation timescale issues are discussed further in the following seetions on double shock waves. 

Figures 16a and 16b show the time evolution of the single-particle second-rank OTCF and the OKE signal derived from the system in log-log plots at several temperatures down to TC. The slowdown in the single-particle dynamics is evident on approaching Tc upon cooling. The single-particle second-rank OTCF shows a shoulder at intermediate timescales below a certain temperature. The shoulder develops into a plateau as the temperature is further lowered. It is evident in Figure 16b that a rather long power law decay regime with a...

The dynamic sUucture factor of the Rouse model is shown in Figure 5(b) for N = 32 and a wide range of vectors. To reveal Rouse-like behavior at intermediate timescales, one can... 

Figure 4 Same data as in Figure 3 normalized by the corresponding scaling behavior at the intermediate timescale.

For highly concentrated polymer solutions, FCS measurements revealed subdiffusive motion as an additional mode on an intermediate timescale between the fast collective diffusion and the slow self-diffusion [24]. In such slow systems, however, FCS reaches its limits when probe motion becomes so slow that the number of molecules moving into or out of the confocal volume within the measurement time is too small to allow for reliable statistics. Increasing the measurement time is often not straightforward since all fluorescence dyes have only a limited photostability. If a dye bleaches within the confocal volume, it will fake a faster diffusional motion than its real value. Therefore, for the study of such concentrated systems, wide-field fluorescence microscopy and subsequent single molecule tracking is a much better method [120] and has been utilized to study the glass transition [87, 121]. 

More recently, another intermediate timescale was explored by NMR relax-ometry [167,168]. The spin-lattice relaxation times of water molecules were determined in the range of 20 ns to 20 (xs by varying the magnetic field fre-... 

This behaviour is usually interpreted in terms of an NMR timescale . For rotation about the C-N bond, which is slow on this timescale at low temperature, the two signals are distinct and relatively sharp. At higher temperature, the rotation is faster and all that we can detect is the average resonance frequency. The broad coalescence line shape is characteristic of the intermediate timescale, and is perhaps the most familiar and obvious manifestation of chemical exchange. In this article we will concentrate on intermediate exchange, because a thorough... 

More recently, another intermediate timescale was explored by NMR relaxom-etry [102]. The spin-lattice relaxation times of water molecules were determined in the range of 20 ns to 20 ps by varying the magnetic field frequency from 10 kHz to 20 MHz and depending on the water content. This technique is well suited for the study of ionomer membranes because of its extreme sensitivity to water-polymer interactions, but it requires a structural and dynamic model to extract characteristic features. The effect of confinement is predominant in polyimides even at high water content (algebraic law with a slope of —0.5 characteristic of porous materials), whereas the diffusion quickly reaches a bulk behavior in Nafion (a plateau is observed at low magnetic fields). 

Note that on a very short timescale (i.e., of the order of the time separating atomic collisions), the instantaneous temperature T(t) is also affected by important stochastic variations (see Sect. 3.2). Only on an intermediate timescale does the mean effect... 

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