Weak decoupling

It has been suggested in the literature [34] that filtration devices producing Taylor or Dean vortices can help depolarization of the solute build up on membranes. This seems to be an attractive way because of excellent bulk fluid mixing, high wall shear rates and weakly decoupled cross-flow with transmembrane flux. Unfortunately there are some severe limitations on a technical and economical point of view with such devices. Build up and scale up of these modules are expensive with difficulties in repairing and changing membranes. A good compromise between economic and technical constraints has been described by Charpin et al. [39]. It consists in the preparation of mineral (metal... 

Fia. 4.—Double-resonance Tickling Experiment on n-Glucal Triacetate The Effect on H-1 of a Weak Decoupling Field Set in the Vicinity of the H-2 Resonance. 

Figure 2. Partial 100 MHz P.M.R. Spectrum of 3,4,6-tri-O-acetyl-v-glucal (1) measured for a chloroform -d solution (A normal spectrum of the Hi and H2 resonances respectively (B) frequency sweep spin-decoupled spectrum of the Hi and H2 resonances, with a strong decoupling field centred on the Hs resonance (C), as in (B) above, but with an additional weak radiofrequency field centred on the high field transition of the H2 resonance (D), as in (B) above, but with a weak radiofreauency field centred on the low field transition...

Experimentally, spin-allowed d-d bands (we use the quotation marks again) are observed with intensities perhaps 100 times larger than spin-forbidden ones but still a few orders of magnitude (say, two) less intense than fully allowed transitions. This weakness of the d-d bands, alluded to in Chapter 2, is a most important pointer to the character of the d orbitals in transition-metal complexes. It directly implies that the admixture between d and p metal functions is small. Now a ligand function can be expressed as a sum of metal-centred orbitals also (see Box 4-1). The weakness of the d-d bands also implies that that portion of any ligand function which looks like a p orbital when expanded onto the metal is small also. Overall, therefore, the great extent to which d-d bands do satisfy Laporte s rule entirely supports our proposition in Chapter 2 that the d orbitals in Werner-type complexes are relatively well isolated (or decoupled or unmixed) from the valence shell of s and/or p functions. 

Figure 42 shows spectra of the simplest tetraorganotin compound, tetramethyltin. The upper spectrum was recorded with complete decoupling of all protons, the middle spectrum without. The result is a multiplet with 13 lines (n = 12), but if you work out the binomial coefficients for such a multiplet you will see that the outer two lines are too weak to be seen. The lower spectrum is the proton spectrum, which shows satellites due to two-bond tin-proton coupling to the tin-117 (inner lines) and tin-119 (outer lines) nuclei. 

The carrier-phonon interaction decreases with the lowering of temperature, since the emission and absorption of phonons by carriers is proportional to the number of final states available to carriers and phonons. At sufficiently low temperatures, the interaction between the two subsystems can be so weak that there is no thermal equilibrium between them, and the energy is distributed among electrons more rapidly than it is distributed to the lattice, resulting in a different temperature for electron and phonon subsystems, giving rise to the so-called electron-phonon decoupling . 

Before ve decoupling at around 1 MeV, neutrons and protons are kept in mutual thermal equilibrium through charged-current weak interactions ... 

Fig. 8. Pulse schemes for 2H 2D NMR spectroscopy of weakly ordered, deuterated solutes (a) 2H Q-COSY, (b) 2H-13C HETCOR experiment with 13C decoupling, (c) 2H-2H COSY 2D experiment. (Reproduced by permission of American Chemical Society.)...

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