Convection artifacts

Jerschow, A. and Muller, N., Suppression of convection artifacts in stimulated-echo diffusion experiments. Double-stimulated-echo experiments, J. Magn. Reson. 125, 372-375 (1997). 

The flow artifacts detected in the droplet size measurements are similar to those reported by Goux et al. [79] and Mohoric and Stepisnik [80]. In their work natural convection effects led to an increase in the decay of signal attenuation curves, causing over-prediction in the self-diffusion coefficient of pure liquids. In order to avoid flow effects in droplet size distributions, flow compensating pulse sequences such as the double PGSTE should be used. It has been demonstrated recently that this sequence facilitates droplet size measurements in pipe flows [81]. 

Another experimental artifact of FFF is the occurrence of ghost peaks . Granger et al. speculated for the case of A-Fl-FFF that such peaks can occur if the sample does not reach its steady state concentration distribution and is thus transported by pure convection in the flow field which can occur at high flow rates [248]. The other peak is that for the separation by diffusion and fits well with theory. 

The thermal conductivity of gaseous COg definitely seems to show a large maximum at the critical point. After Sengers and Michels careful work, an explanation based on experimental artifacts such as convection would be difficult to sustain. 

Contrary to the results for labile Ni, the gradients of relative concentrations of dissolved Ni obtained with the model including exudation (Model 3) matched water-extractable Ni data better (Fig. 2b). The curves produced by the other models were more discrepant. Water extracts may not represent real soil solutions and freezing of soil samples might have introduced additional artifacts. However, gradients of Ni concentration in soil solution were not available. Water-extractable Ni data in Fig. 2b are presented for orientation but caimot be used for proper model corroboration. All simulated curves were opposite to the trend implied by measured water-extractable Ni. Accumulation of solutes near the root is known for excluders or for situations where convective flow toward the root exceeds plant demand. This was not the case in our experimental system. In future experiments, the use of microsuction cups will enable comparison of simulated and measured dissolved Ni (Wenzel et al., 2001). 

Temperature is an important parameter which can significantly influence the properties and applicability of polymer systems. In order to capture all the interesting transitions in polymers, it is of considerable interest to be able to perform FCS measurements in polymers in an extended temperature range from cryogenic temperatures up to several hundred degrees centigrade with accurate temperature control and without artifacts from temperature gradients or convection. A setup... 

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