Other relaxation experiments

The jump rates obtained by the line shape simulations are plotted on the relaxation map in Fig. 22 together with values obtained by other experimental methods. The points of the mechanical and dielectric relaxations correspond to the process of the large-scale side chain motions refered to as the -process and follow the WLF equation very well above Jg,. 11 It should be noted that the present 2FI NMR results are located on the curve obtained by other relaxation experiments. This fact shows that... 

The kLAM of PBLG-yd2 obtained are located on the WLF curve obtained by other relaxation experiments, showing that the motional mechanism of the... 

The time-resolved solvation of s-tetrazine in propylene carbonate is studied by ultrafast transient hole burning. In agreement with mode-coupling theory, the temperature dependence of the average relaxation dme follows a power law in which the critical temperature and exponent are the same as in other relaxation experiments. Our recent theory for solvation by mechanical relaxation provides a unified and quantitative explanation of both the subpicosecond phonon-induced relaxation and the slower structural relaxation. 

Although a set of N R, R2, and N- H NOE is commonly used to characterize backbone protein dynamics, other relaxation experiments are also useful to characterize protein dynamics. Use of other than three experimental data allows an application of a more detail dynamics model than the conventional model-free model. For example, cross-correlated longimdinal (rjz) and transverse ( xy) rates between DD and N CSA have provided useful information about protein... 

Other viscoelastic experiments can be performed but often the slow relaxation processes make it difficult to achieve an equilibrium response. 

Thus for undiluted polymers the relaxation behaviour can be examined over a wider range of apparent frequencies. Similar functions can be constructed for other regions of the phase diagram and other rheological experiments. The method of reduced variables has not been widely tested for aqueous crosslinked polymers. Typically these are polyelectrolytes crosslinked by ionic species. Some of these give rise to very simple relaxation behaviour. For example 98% hydrolysed poly(vinyl acetate) can be crosslinked by sodium tetraborate. The crosslink that forms is shown in Figure 5.31. 

It proved helpful for the purpose of noise reduction to perform relaxation experiments in an interleaved fashion, as one pseudo-3D experiment, where the 2D planes in the F2 dimension correspond to various relaxation delays. The acquisition order (3-2-1) is selected so that cycling through various relaxation delays (in R1 or R2 experiments) or through NOE/NONOE 2D planes is performed prior to incrementing the evolution period in the indirect dimension (FI) (see e.g. Ref. [16]). The resulting pseudo-3D spectrum can be processed as a set of 2D spectra in tl and t3 dimensions, and then analyzed in the usual way. This procedure reduces the noise arising from switching from one 2D experiment to the other and helps minimize temperature variations between the spectra acquired... 

Besides the advantage of the high-temperature measurements for quantitative interpretation of NOESY spectra, fig. 6 also indicates a special role of the high temperature maximum (note that positive cross-relaxation rates increase downward) of u". If the NOESY spectrum can be recorded at several temperatures around the cr" maximum, than calculated cross-relaxation rates can be used to obtain simultaneously the correlation time and the interproton distances without the necessity of any other knowledge. A typical problem in the cross-relaxation experiments is that cross-relaxation rate depends on two parameters, Tc and r (eq. (la)), and to calculate one of them the other must be independently known. However, the position of the maximum uniquely determines correlation time, and its height uniquely determines interproton distances. 

The experiment is applied for the evaluation of C T, values. T, values are usually used to optimize insensitive C experiments, i.e. to adjust the length of the preparation time in other NMR experiments. To deduce structural information it is usual to interpret the dipolar part of the longitudinal relaxation time (T, ). To separate the dipolar contribution from the contributions of other relaxation mechanisms, it is necessary to perform further experiments (gated decoupling experiments) to evaluate the heteronuclear NOE values. T °° may be exploited in a qualitative way to differentiate between carbon nuclei in less or highly mobile molecular fragments. In a more detailed analysis reliable T, values can be used to describe the overall and internal motions of molecules. 

By assuming an Arrhenius type temperature relation for both the diffusional jumps and r, we can use the asymptotic behavior of /(to) and T, as a function of temperature to determine the activation energy of motion (an example is given in the next section). We furthermore note that the interpretation of an NMR experiment in terms of diffusional motion requires the assumption of a defined microscopic model of atomic motion (migration) in order to obtain the correct relationships between the ensemble average of the molecular motion of the nuclear magnetic dipoles and both the spectral density and the spin-lattice relaxation time Tt. There are other relaxation times, such as the spin-spin relaxation time T2, which describes the... 

The initial effects felt similar to my other Salvinorin experiments in that I found myself relaxing in a state of immensely expanded awareness. 

Coherent transport of vibrational energy is further limited by vibrational energy relaxation. Experiments on the amide I band of different peptides (NMA, apamin, scyllatoxin BPTI, and the cyclic pentapeptide) revealed a vibrational relaxation rate of approximately Ti = 1.2 ps, which is essentially independent of the particular peptide (30,53). A similar value has recently been reported for myoglobin at room temperature, with only a weak dependence of the relaxation rate on temperature down to cryogenic temperatures (140). In other words, vibrational relaxation of the amide I mode reflects an intrinsic property of the peptide group itself rather than a specific characteristic of the primary or secondary structural motifs of the... 

Very few experiments have been performed on vibrational dynamics in supercritical fluids (47). A few spectral line experiments, both Raman and infrared, have been conducted (48-58). While some studies show nothing unique occurring near the critical point (48,51,53), other work finds anomalous behavior, such as significant line broadening in the vicinity of the critical point (52,54-60). Troe and coworkers examined the excited electronic state vibrational relaxation of azulene in supercritical ethane and propane (61-64). Relaxation rates of azulene in propane along a near-critical isotherm show the three-region dependence on density, as does the shift in the electronic absorption frequency. Their relaxation experiments in supercritical carbon dioxide, xenon, and ethane were done farther from the critical point, and the three-region behavior was not observed. The measured density dependence of vibrational relaxation in these fluids was... 

The thickness of the adsorption layer was estimated from the fraction of adsorbed chain units measured by means of h Ty, Tj and H relaxation studies [7, 8, 10, 12]. From the known value of the specific surface of Aerosil, its volume fraction in mixtures and the fraction of low mobile chain units at the Aerosil surface, the thickness of the adsorption layer is estimated assuming imiform coverage of the filler particles by a PDMS layer of constant thickness. This calculation leads to a value of about 0.8 run [7]. This value is increased by a factor 1.5-2, if a part of the filler surface will not be accessible for PDMS chains due to direct contacts between the primarily filler particles in aggregates [27]. Thus, the chain adsorption causes a significant restriction of local motions only in one or two monolayers adjacent to the filler surface. A similar estimation of the adsorption layer thickness has been obtained by other methods such as, e.g. dielectric experiment [27], adsorption study [3], the viscosity of the boundary layer for silicon liquids at the surface of a glass [5], molecular dynamics simulations [6], and C NMR relaxation experiments [22]. 

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