Driven equilibrium

Polarization transfer techniques like INEPT and DEPT have been used to enhance sensitivity in heteronuclear 2D /-resolved spectra. In combination with the semiselective sequence just described, INEPT has been used to suppress long-range Jen couplings and to measure the one-bond couplings (Fig. 5.15) (Rutar, 1984). Driven equilibrium pulses for fast restora-... 

Ochiai s landmark paper of 1967, which outlined the basis of the 1,3-APT (Section 1.11.1), also described the reaction of formaldoxime with alkenes and alkynes (284). The oxime 310, behaving as a 1,3-dipole, afforded isoxazolidine cycloadducts 311 through a thermally driven equilibrium (heavily favoring the oxime) in which a proton is transferred from O to N (1,2-prototropy) to afford nitrone 312 (Scheme 1.65). 

The third method involves a three pulse sequence, 90 — r — 180° — x — 90°, with a repetition time of tr s. This pulse sequence refocuses the magnetization vector M0 into its equilibrium position within the repetition time, thus representing a pulse driven relaxation acceleration. This technique, known as DEFT NMR [23, 24] (driven equilibrium Fourier transform NMR) can be understood by following the behavior of the magnetization vector Mq under the influence of the pulse sequence in the rotating frame of reference (Fig. 2.17(a-e)). 

Fig. 2.17. Driven equilibrium FID (a) — (b) — (c) — (d) — (e) — (a) the sample magnetization following a 90", t, 180°, r. 90° pulse sequence (f) and (g) comparison between the FID signals following repetitive 90 pulses and those following repetitive 90c, r, 180°, r, 90" pulse sequences example 13C FID of enriched carbon tetrachloride, 13CC14.

Figure 8 Molecular stmcture of spirooxazine (SO) dyes (10) and their light-driven equilibrium...

One way to increase the efficiency of data taking in such a case is a sequence called DEFT for driven equilibrium Fourier transform (Becker, et al. 1969). The idea of this experiment is to force the system back to equilibrium more rapidly after each FID so that it can be pulsed more frequently. In a DEFT sequence, a 90° pulse is applied to the system, and the FID is recorded. A 180° pulse is applied at a time x when the FID has disappeared due to the dephasing of the spin isochromats to form an echo at time 2x. At the... 

Edwin D. Becker, James A. Ferretti and T. C. Farrar, Driven equilibrium Fourier transform spectroscopy. A new method for nuclear magnetic resonance signal enhancement," J. Am. Chem. Soc. 91, 7784-7785 (1969). 

Doebber M, Bordignon E, Klare JP, Holterhues J, Martell S, Mennes N, Li L, Engelhard M, Steinhoff HJ (2008) Salt-driven equilibrium between two conformations in the RAMP domain from N. pharaonis the language of signal transduction J Biol Chem 283(42) 28691-28701... 

Furthermore, there have been developed special pulse methods (DEFT and SEFT, i.e. driven equilibrium Fourier transform and spin-echo Fourier transform method) for extremely slowly relaxing The cosine... 

The adsorption of vapor is a physical process which can be reversed. Desorption of vapor does not require a high energy and is equilibrium driven (equilibrium relative to the concentration of vapor in surrounding atmosphere and distribution of adsorbed vapor in... 

In Section 6.3.1, we cover external forces, specifically gravitational, electrical and centrifugal forces inertial force is also included here. In Section 6.3.2, chemical potential gradient driven equilibrium separation processes involving vapor-liquid, liquid-liquid, solid-melt and solid-vapor systems are considered the processes are flash vaporization, flash devolatilization, batch distillation, liquid-liquid extraction, zone melting, normal freezing and drying. Section 6.3.3 illustrates a number of membrane separation processes in the so-called dead-end filtration mode achieved when the feed bulk flow is parallel to the... 

Gated double resonance Selective population transfer (SPT) Selective population inversion (SPI) Double-selective population transfer Recovery of inhomogeneity broadening Driven equilibrium FT (DEFT)... 

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