Diffusion analysis

It is interesting to note that Johansson andLofroth [183] found i to equal 1.09 for the diffusion analysis, but the partition coefficient followed a streched exponential with varying i from 1 to 2, indicating that the ratio of diffusion coefficient is not equal to the accessible volume fraction for large molecules, as is assumed in the ORMC model for gel electrophoresis. 

In 1902, Wagner published an analysis, based on diffusion reactions, of the oxidation of the surface of a metal. His interpretation has remained a classic in solid state diffusion analysis. The surface of a metal consists of metal atoms bound to the inner structure by a series of hybrid-bonds. If oxygen gas is present (air), the metal can form an oxide coating ... 

Modeling relaxation-influenced processes has been the subject of much theoretical work, which provides valuable insight into the physical process of solvent sorption [119], But these models are too complex to be useful in correlating data. However, in cases where the transport exponent is 0.5, it is simple to apply a diffusion analysis to the data. Such an analysis can usually fit such data well with a single parameter and provides dimensional scaling directly, plus the rate constant—the diffusion coefficient—has more intuitive significance than an empirical parameter like k. 

Notice that as the radiant flux <2r increases, E and the term 5/(1 - E) increase. When E = 1, the problem disintegrates because the equation was developed in the framework of a diffusion analysis. E = 1 means that the solid is gasified by the radiant flux alone. 

Fig. 6. Variation of Tc with time (transport coefficient obtained from diffusion analysis of results from open-ended capillary) for the [3H]PVP 360 ( ) and [uC]sorbitol (O) transport in standard solution systems (described in the legend to Fig. 5) 47>...

When the activation process is comparable with or slower than the rate of approach of reactants to form encounter pairs, it is no longer satisfactory to say that the reactants can not co-exist within a distance R of one another. Because the rate of reaction, /eact, of the activation process is finite, so too is the lifetime (and hence concentration) of encounter pairs non-zero. The inner boundary condition, which describes reaction of A and B together in the diffusion analysis, is unsatisfactory. Collins and Kimball [4] suggested an alternative boundary condition and the remainder of this section analyses their work following Noyes [5]. Firstly, the boundary condition is developed and then included in the diffusion equation analysis to obtain the density distribution. Finally, the rate coefficient is obtained. 

We have established that the volume change kinetics of responsive gels are usually diffusion-controlled processes. Even when the diffusion analysis failed, the rates were comparable to or slower than a classical diffusive process. The implications of this for practical applications are quite negative, since diffusive processes are quite slow. A gel slab 1 mm thick with a diffusion coefficient of 10-7 cm2/s will take over an hour to reach 50% of equilibrium and more than six hours to reach 90% of equilibrium in response to a stimulus. This is far too slow for almost all potential applications of these materials. Since diffusion times scale with the square of dimension, decreasing the characteristic dimension of a sample will increase the rates dramatically. Thus if an application can make use of submillimeter size gels, millisecond response times become possible. Unfortunately, it may not always practical to use gels of such small dimension. 

Lehmenkiihler A, Sykova E, Svoboda J, Zilles K, Nicholson C. Extracellular space parameters in the rat neocortex and subcortical white matter during postnatal development determined by diffusion analysis. Neuroscience 1993, 55, 339-351. 

No, H-C., et al. (2007), Multi-component Diffusion Analysis and Assessment of GAMMA Code and Improved RELAP5 Code , Nucl. Eng. and Design, 237, 997-1008. 

Nicholson C, Sykova E (1998) Extracellular space structure revealed by diffusion analysis. Trends Neurosci 21 207-215... 

As revealed by gel electrophoresis and agar diffusion, two new antigenic substances were obtained as the major components of extracts of human colon tumors with the KC1-HC1 solution. The coupled electrophoresis-agar diffusion analysis showed that the components reacted with immune serum from rabbits immunized with new antigens. These antigens are present in colon tumor tissue but were not present in normal colon tissue. The... 

Fig. (34). Coupled electrophoresis - agar diffusion analysis of tumor extracts and immune serum A Perchloric acid extract (CEA, 1-4) normal extract (5) B.KCI-HCI extract (6-9).

Sub-diffraction diffusion analysis within lipidic membranes... 

Wenger, J., Conchonaud, F., Dintinger, J., Wawrezinieck, L., Ebbesen, T. W., Rigneauit, H., Marguet, D., and Lenne, P. F. (2007). Diffusion analysis within single nanometric apertures reveals the ultrafine cell membrane organization. Biophys. J. 92 913-919. 

B Perform a transient mass diffusion analysis in large mediums,... 

Recent improvements in techniques of sedimentation and diffusion analysis have permitted their application to materials in the molecular-weight range of the Schardinger dextrins. These measurements supplement other types of determinations in that (1) they are not particularly sensitive to the presence of low molecular-weight impurities, and (2) the sedimentation and diffusion constants can be extrapolated to infinite dilution to eliminate aggregation and interaction effects. 

E. L Hostis, C. Compare, D. Festy, B. Tribollet, and C. Deslouis, "Characterization of Biofilms Formed on Gold in Natural Seawater by Oxygen Diffusion Analysis," Corrosion, 53 (1997) 4-10. 

Nielsen, D.R., J.W. Biggar, and J.M. Davidson. 1962. Experimental consideration of diffusion analysis in unsaturated flow problem. Soil Sci. Soc. Am. Proc. 26 107-111. 

The setup for thermal diffusion analysis contains two cylinders installed one in another as shown in Figure 2.60. The sample is introduced between these two cylinders. During analysis, the wall of one cylinder is heated up to a temperature... 

High resolution 13C NMR spectroscopy was used to analyze miscibility of POM with terphenol (MW = 600 g/mol). The size of the heterogeneity in the amorphous phase was estimated as 1 nm. The IH spin diffusion analysis indicated a homogenous mixing on the molecular level [Egawa et al, 1996]. 

P-16 - Diffusion analysis of cumene cracking over ZSM5 using a jetloop reactor... 

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