Counter-diffusion apparatus

The crystals of NCPs containing a-satellite DNA palindrome and chicken erythrocyte histones diffracted isotropically to 3.0 A using an in-house rotating anode X-ray source and to better than 2.5 A at a moderate intensity synchrotron beamline [30,31]. The crystals used for structure determination were grown in the microgravity environment using a counter-diffusion apparatus [32]. Ground-based... 

After being washed (for total process overview cf. Figure 9.3.5) the beets are sliced into strips (cossettes), which afterwards are fed into the so-called diffusers where about 98% of the sucrose is extracted. High temperatures (65-70 °C) in the diffusion apparatus denature the plant cells and open the cell membranes for improved sucrose transfer. The entire extraction of the sucrose is carried out via a counter current flow of the extraction medium, i.e. water and the denatured cossettes. 

The determination of transport numbers in aqueous electrolytes is relatively easy (Chapter 3), but in molten salts it poses difficulties of concept, which in turn demand specialized apparatus. Explain why direct determination is difficult. Would it not be better to abandon the direct approach and use the approximate applicability of the Nernst-Einstein equation, relying on self-diffusion determinations Any counter considerations ... 

The experimentally performed transport processes used for evaluation of transport parameters include counter current binary or multicomponent gas diffusion under steady-state or chromatographic conditions, steady permeation of simple gases, dynamics of combined transport of binary or multicomponent gas mixtures, etc. Of significance, however, is that no automatic commercial instrument is available for these processes. Thus, the necessary apparatuses must be homemade. To obtain the transport parameters with acceptable confidence large numbers of experiments is required. It would be, therefore, of significant importance if at least part of the transport parameters could be obtained from standard textural analysis. 

Surface self-diffusion is the two-dimensional analogue of the Brownian motion of molecules in a liquid bulk. Measurements of self-diffusion have to be performed in complete absence of any Marangoni flow caused by surface tension differences. Such experimental conditions are best established in an insoluble monolayer where one part consists of unlabelled and the other of radio-tracer labelled molecules. The movement of molecules within the surface monolayer can be now observed by using a Geiger-Miiller counter. There are possible effects of liquid convective flow in the sublayer which was discussed for example by Vollhardt et al. (1980a). With e special designed apparatus Vollhardt et al. (1980b) studied the self-difihision of different palmitic and stearic acid and stearyl alcohol and obtained self-diffusion coefficients between l-i-4 lO cm /s. 

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