Concentration profiles during formation

The evidence of interference microscopy nicely correlates with the models of crystallization, which in the case of SAPO-5 favor a pencil-like crystallization core [79,80], while in CrAPO-5 crystalUzation proceeds via the formation of dumbbell-shaped structures [81,82]. In no case coifid a nanoporous material with the desired structure of microscopic, ideal macaronis be identified. The appearing dramatic deviation from an ideal channel structure excludes the appHcation of simple model assiunptions for interpretation of the time evolution of the concentration profiles, hi fact, in [83] the experimentally monitored concentration profiles during... 

In the case of short-term catalysis, the basic processes of formation of the products occur in the gas phase after the interaction with the catalyst, which removes many of the issues related to changes in its properties under the influence of the products, for example, because of their deposition on the surface. High gas flow rates ( 1 m/s) and short contact times ( 1 ms) enable to produce a few kilograms of products per day per less than 1 g of catalyst [155]. Short-term catalysis makes it possible to realize complex combinations of temperature and concentration profiles during the reaction, as well as various versions of the relationship between the areas of catalytic and gas phase processes. 

FIG. 18 Chloride concentration profile recorded by a microelectrode probe during the hydrolysis of TPMCl at a DCE drop-aqueous interface (O)- The concentration of TPMCl in the organic phase was 50 mmol dm, the drop time from formation to contact with the probe was 4.80 s, and the final drop radius was 0.55 mm. The solid lines represent theoretical time-dependent concentration profiles, from top to bottom, generated for k = 3.50 x 10 , 3.25 x 10 , and 3.00 x 10 molcm s . A value of 1.8 X 10 cm s was employed for the diffusion coefficient of chloride. (Reprinted from Ref. 73. Copyright 1997, American Chemical Society.)... 

The breakthrough time observed in the NO, concentration profile indicates that during the initial part of the pulse the N O fed to the reactor is completely stored on the catalyst surface. As shown by FT-IR spectroscopy [inset (d) in Figure 13.12], the initial NO uptake occurs primarily in the form of nitrites, which are readily transformed into nitrates so that at the end of the NO pulse, at catalyst saturation, nitrates were the prevalent species. Notably, the rate of both nitrite formation and their oxidation to nitrates was higher on Pt-Ba/y-AbOj than on Ba/y-AbO, thus indicating a catalytic role of Pt. 

The ultimate levels of esters in fresh and stored apples are determined by the amount of precursors for ester formation, e.g. lipids, which are influenced by cultivar, growing conditions, harvest maturity and storage conditions [47]. In Fuji apples, acetate ester concentrations increase during maturation, 2-methyl-butyl acetate being the major ester component in the volatile compound profile... 

To shed light on the mechanism of formation of silsesquioxane a7b3, to identify the species formed during the process, and to try to explain the high selectivity towards structure a7b3 of the optimised synthetic method described above (64% yield in 18 h), the synthesis of cyclopentyl silsesquioxane a7b3 was monitored by electrospray ionisation mass spectrometry (ESI MS) [50-52] and in situ attenuated total reflection Fourier-transform infrared (ATR FTIR) spectroscopy [53, 54]. Spectroscopic data from the latter were analysed using chemometric methods to identify the pure component spectra and relative concentration profiles. 

Formation or consumption of reacting species at the electrode surface causes concentration distribution of electroactive species in the solution phase during electrolysis. Equi-concentration contours stand for a concentration profile. A concentration profile can be measured by detecting current or potential by use of a small probe electrode at various locations near a target large electrode. A typical method is scanning electrochemical microscopy. See also diffusion layer, - scanning electrochemical microscope. 

Figure 13. Concentration profiles of the precipitant in the casting solution at various times during the formation of a symmetric structured membrane.

Rationalization of the Verious Membrane Preparation Procedures. To discuss the formation of membrane structures it is useful to describe the concentration profiles of the casting solution components in the precipitating casting solution. The schematic diagram of Figure 1.21 shows the concentration profiles of polymer, solvent and precipitant at some intermediate time during the precipitation of a polymer film cast on a glass plate. 

Temperature Effects During the condensation/evaporation of a particle latent heat is released/absorbed at the particle surface. This heat can be released either toward the particle or toward the exterior gas phase. As mass transfer continues, the particle surface temperature changes until the rate of heat transfer balances the rate of heat generation/ consumption. The formation of the external temperature and vapor concentration profiles must be related by a steady-state energy balance to determine the steady-state surface temperature at all times during the particle growth. 

In ppKCE, the plugs of L and T are injected into the capillary prefilled with the run buffer. The inlet and outlet reservoirs contain the run buffer as well. During electrophoresis T moves through L causing the formation of C. When the zone of T passes L, C starts to dissociate. ppKCE can be considered as a functional hybrid of NECEEM and SweepCE. The resulting concentration profiles... 

A very elegant approach overcoming this problem has been proposed based on a channel flow cell geometry with downstream detection (Fig. II.6.2d). The potential of the electrode is stepped during steady-state flow of the solution across the electrode. A downstream UVA is detector system is then employed to measure the time dependence of the concentration profile formation at the electrode surface. A computer program is employed to relate the time-dependent absorbance signal to the concentration profile of reactant and product at the electrode surface. Alternatively, direct measurement of the concentration profiles at the electrode surface has also been reported based on confocal Raman spectroelectrochemistry [16]. 

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