Attenuation relaxation

Pervushin, K., Riek, R., Wider, G., and Wiithrich, K. 1997. Attenuated relaxation by mutual cancellation of dipole-dipole coupling and chemical shift anisotropy indicates an avenue to NMR structures of very large biological macromolecules in solution. Proc. Natl. Acad. Sci. USA 94 12366-12371. 

Ultrasonic absorption is used in the investigation of fast reactions in solution. If a system is at equilibrium and the equilibrium is disturbed in a very short time (of the order of 10"seconds) then it takes a finite time for the system to recover its equilibrium condition. This is called a relaxation process. When a system in solution is caused to relax using ultrasonics, the relaxation lime of the equilibrium can be related to the attenuation of the sound wave. Relaxation times of 10" to 10 seconds have been measured using this method and the rates of formation of many mono-, di-and tripositive metal complexes with a range of anions have been determined. 

For phase encoding the phase twist is most connnonly varied by incrementing in a series of subsequent transients as tiiis results in a constant transverse relaxation attenuation of the signal at the measurement position. The signal intensity as a fiinction of G is... 

Condensed phase vibrational or vibronic lineshapes (vibronic transitions create vibrational excitations of electronic excited states) rarely provide infonnation about VER (see example C3.5.6.4). Experimental measurements of VER need much more than just the vibrational spectmm. The earliest VER measurements in condensed phases were ultrasonic attenuation studies of liquids [15], which provided an overall relaxation time for slowly (>10 ns) relaxing small molecule liquids. 

The thorough and persistent work on precursor decay (the dependence of Hugoniot elastic limit on propagation distance) of Duvall s Washington State University group was successful in demonstrating that precursor attenuation was due to both stress relaxation and hydrodynamic attenuation. Typical data on crystalline LiF is shown in Fig. 2.7. Observed plastic strain... 

Oyama, Y., Kawasaki, H., Flattori, Y. and Kanno, M. (1986). Attenuation of endothelium-dependent relaxation in aorta from diabetic rats. Eur. J. Pharmacol. 131, 75-78. 

In Temkin s analysis, mass transfer is assumed to be absent in the two-component system. He found that an attenuation coefficient, A, is function of the relaxation times td and t, and the mass fration of suspension, x . 

Temkin, S., 1966, Attenuation and Dispersion of Sound by Particulate Relaxation Processes, Brown University (available from DDC as AD-630326). (3)... 

Several NMR pulse sequences have been developed for measuring the diffusion coefficient. The most successful and currently used experiment is the modified spin-echo experiment (PGSE) proposed by Stejskal in 1967.62 As the echo signal is due to the transversal components of magnetic moments, the echo attenuation normalized for the attenuation due to relaxation can be written as63 ... 

Unavoidably, the efficiency of the different low-pass J filters in removing direct correlations induces attenuation of the signals associated with long-range couplings. For some molecules, the choice of the most suitable low-pass J filter may be first determined by the attenuation of those signals. Neglecting relaxation, pulse imperfections and offset effects, the... 

The results shown in Figure 8 are in good agreement with the theoretical results shown in Table 2. The value of the 2/c2hi coupling is very large, 49 Hz, and the attenuation during the respective low-pass J filters is subsequent (left). It must be pointed out that relaxation has not been... 

Regarding the vasculature, treatment of aortic rings with mtALDH inhibitors attenuated GTN-dependent relaxation, formation of 1,2-GDN and accumulation of cGMP. Moreover, when tolerance was induced by pre-treatment with GTN, generation of 1,2-GDN and cGMP were again decreased, as was the activity of mtALDH. In whole animals, ALDH inhibitors were shown to attenuate the hypotensive effects of GTN in rabbits and rats. 

Fig. 15.2 Ty, experiments performed on a mixture of para-hydroxy-benzanilide (1) and five other compounds with FKBP. Spectra in the upper and lower row correspond to spin-lock periods of 10 ms and 200 ms, respectively. Higher attenuation at 200 ms, as visible in the SLAPSTIC spectra (right) means faster relaxation in the bound state...

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