Mobility factor

Three factors seem to be important for enantioselectivity to occur on surfaces the steric factor, the polar factor, and the mobility factor. Each of these... 

The mobility factor acknowledges the fact that organic molecules seem to move about on surfaces. For example, Blackmond and Augustine and associates have identified an induction period in the cinchona alkaloid modified... 

F —mobilization factor as a ratio of anthropogenic emission into the atmosphere to the natural one... 

The electroosmotic velocity is characterized by a mobility factor, namely the electroosmotic mobility (/ieof)=... 

Fig. 6 Dependence of migration activation enthalpy on preexponential mobility factor for tilt grain boundaries in Al I ( ) and Al II...

In the model, Xp is determined by a temperature dependent electrophoretic mobility factor [123] which contains the viscosity of the solvent as well as its relative permittivity, Xc °, the radius of the polymer chain and the Debye screening length 1D. The following equation holds for the case that electrolyte and polyelectrolyte are in the same concentration range ... 

The formal description of thermodiffusion in the critical region has been discussed in detail by Luettmer-Strathmann [79], The diffusion coefficient of a critical mixture in the long wavelength limit contains a mobility factor, the Onsager coefficient a = ab + Aa, and a thermodynamic contribution, the static structure factor S(0) [7, 79] ... 

Figure 4 Effects of chemical treatments on relationships between logarithm of E l 7 and logarithm of tan 6. Dotted lines represent experimental correlations for untreated specimens. Various values of relative increase of matrix rigidity (/ ) and mobility factor (jx) were simulated. (A, A) Experimental values of untreated and treated specimens. (O, ) Theoretical plots for zero mean microfibrillar angle and theoretical plots assuming swelling effect only. See legend to Fig. 2 for treatment abbreviations.

The mobility factor M (T) describes the segmental mobility of the chain it depends mostly on temperature and pressure, but may be affected by the presence of small chains (such as solvent molecules or sm l chains of the same chemical species as the polymer). For concentrated polymer solutions, the addition of small molecules affects mostly the glass transition temperatm-e (hence Too), and the value of B (eq.2-20) is essentially the same as for the bulk polymer. A plastifyer will decrease the value of Too, and hence increase the segmental mobility. On the contrary, the addition of a tackifying resin which has a higher Tg than the polymer will increase the segmental mobility of the polymer in the case of formulations of Hot-Melt adhesives. 

The structure factor (P(M)) describes the topological relaxation of the macromolecular chains this is the function which will be described by molecular models, P(M) being the distribution of moleciilar weights. Here lies a very important point if one wishes to "isolate" the topological effects in order to test molecular models, one has to use rheological functions defined at the same segmental mobility, and hence the same value of the mobility factor as far as viscosity is concerned, the reduced function (T) will be used instead of the viscosity itself. 

All viscoelastic functions may be expressed in terms of a single reptation parameter (for example the plateau modulus or tube diameter) and the monomeric friction coefficient (or mobility factor in our terminology), in agreement with the above phenomenological presentation. 

Another deviation from the pattern of ordinary diffusion must be expected if the reactant and product molecules are subjected to single-file conditions, i.e. if (i) the zeolite pore system consists of an array of parallel channels and if (ii) the molecules are too big to pass each other. In this case, the molecular mean-square displacement z t)) is found to be proportional to the square root of the observation time, rather than to the observation time itself. First PFG NMR studies of such systems are in agreement with this prediction [8]. By introducing a mobility factor F, in analogy to the Einstein relation for ordinary diffusion. 

Under the assumption that molecular propagation in single-file systems proceeds by activated jumps of step length I with a mean life time r between succeeding jump attempts, and that jump attempts are only successful if they are directed to a vacant site, the mobility factor may be shown to be given by the relation [10]... 

D. H. Oughton, B. Salbu and P. Strand, Mobility Factors for Estimating the Bioavailability of... 

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