Coherent flow

We first examine how this works for the case of coherent flow. A typical pulse sequence is shown in figure Bl.14.9. This sequence creates a spin echo using two unipolar gradient pulses on either side of a 180° pulse. The duration of each gradient pulse of strength G, is . The centres of the gradient pulses are separated by A. 

The exponent turned out to be x 1. This finding demonstrates that coherent flow determines transport in the mechanical dispersion regime and that diffusion is negligible under such conditions. For a discussion also see Ref. [43]. 

Reactors which generate vortex flows (VFs) are common in both planktonic cellular and biofilm reactor applications due to the mixing provided by the VF. The generation of Taylor vortices in Couette cells has been studied by MRM to characterize the dynamics of hydrodynamic instabilities [56], The presence of the coherent flow structures renders the mass transfer coefficient approaches of limited utility, as in the biofilm capillary reactor, due to the inability to incorporate microscale details of the advection field into the mass transfer coefficient model. 

The HNCA-TROSY experiment can be readily extended to correlate the 13C spin of the preceding residue with intraresidual 11 IN(/), 15N(i), and 13C° (/ ) frequencies. This kind of four-dimensional HNCO CA-TROSY experiment (Fig. 7) was recently introduced by Konrat et al.79 The coherence flows through the following pathway... 

N single quantum coherence. The chemical shift of 15N is recorded in a (semi-)constant-time manner during t2 and ultimately the 15N-1Hn PEP-TROSY element selects the most slowly relaxing 15N Hn multiplet component prior the acquisition. The coherence flow can thus be described as... 

Now that we know most of the basic building blocks of NMR pulse sequences, we should be able to use the coherence flow diagram (Fig. 11.9) to design an HSQC pulse sequence. It needs to accomplish the following steps ... 

The experiment can also be run in the other sense, with the TOCSY part first and the HSQC second (Fig. 12.46, bottom). This 3D experiment is called a TOCSY-HSQC, and the coherence flow is diagramed in Figure 12.48. Coherence is created on all protons (Hn,... 

The distributed array of drag elements in vegetation canopies creates a mean wind profile that contains an elevated shear layer centred near the canopy top that more closely approximates a plane mixing layer than a wall layer. This velocity stmcture is responsible for turbulence characteristics that differ substantially from those over a smooth surface. Velocity spectra are sharply peaked, streamwise and vertical velocities have probability densities that are strongly skewed, streamwise and vertical velocities are correlated more strongly that would be expected over a smoother surface, and transport is dominated by coherent flow structures with sweeps more important than ejections. 

Incoherent flow is often referred to as pseudo-diffusion. An apparent diffusion coefficient which can be significantly bigger than the self-diffusion coefficient is then defined. Pulse sequences to measure coherent flow (figure B 1.14.9) can also be used for (spatially) incoherent motion although the theory has to be reconsidered at this point [M, M and M] ... 

Tsujimoto, T. 1996. Coherent fluctuations in a vegetated zone of open-channel flow Cause of bedload lateral transport and sorting. Coherent Flow Structures in Open Channels, edited by P.J. Ashworth, S.J. Bennett, J.L. Best S.J. McLelland, John Wiley Sons 375-396. 

The analysis of the influence of particle clustering on the heat and mass transfer within the spray has been investigated. Especially in the hot gas atomization process, the preferential concentration of particles is an important mechanism that increases the inhomogeneity in the spray. The cluster structures strongly depend on the local Stokes number and their formation is induced by coherent flow structures of the continuous gas phase. 

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