Migrants, Migration

Typical polymers Potential migrants Migration risk Hazard assessment... 

The relative displacement rates of the interfaces AIAB and ABIB in any particular system will, of course, depend on the relative migration velocities of all mobile participants across the barrier layer and reaction will continue while appropriate reactant constituents remain available. Such migrant entities travel by the most efficient route and therefore overall rates of such reactions are frequently sensitive to the concentration of imperfections in the product crystal lattice [1171]. One possible... 

Two product barrier layers are formed and the continuation of reaction requires that A is transported across CB and C across AD, assuming that the (usually smaller) cations are the mobile species. The interface reactions involved and the mechanisms of ion migration are similar to those already described for other systems. (It is also possible that solid solutions will be formed.) As Welch [111] has pointed out, reaction between solids, however complex they may be, can (usually) be resolved into a series of interactions between two phases. In complicated processes an increased number of phases, interfaces, and migrant entities must be characterized and this requires an appropriate increase in the number of variables measured, with all the attendant difficulties and limitations. However, the careful selection of components of the reactant mixture (e.g. the use of a common ion) or the imaginative design of reactant disposition can sometimes result in a significant simplification of the problems of interpretation, as is seen in some of the examples cited below. 

These are reasonable KIEs for a secondary isotope effect in a 1,2-C migration, and originate from the hybridization changes at the migrant carbon (sp2,6 -> sp24) QMT is therefore not invoked.77... 

The product ratio a /b (statistically corrected for the number of competing H migrants), gives the relative migration rate of Ha vs. Hb, or k /kub- The rate constant for the migration of Ha corresponds to the intrinsic migratory aptitude of Ha (M[H]) multiplied by the bystander assistance factor for Y, B[Y], The carbon atom that bears Hb has no bystander substituent, so that km, is simply A/[H], We thus obtain Eq. 24. 

The bystander substituent (Y) exerts a direct influence on the migrant group (M) at the migration origin. In contrast, a spectator substituent (X in Eq. 22)... 

Spectator substituents, bonded to the carbene s migration terminus (Ci), directly influence the lifetime and philicity of the carbene, but they do not primarily alter the migratory aptitudes of migrants on C2. Oxa spectator substituents stabilize singlet carbenes by electron donation to the vacant carbenic p orbital (LUMO) cf. resonance hybrid 69. 

Soto-Valdez, H., Gramshaw, J.W. and Vandenburg, H.J. (1997). Determination of potential migrants present in Nylon microwave and roasting bags and migration into olive oil, Food Addit. Contam., 14, 3, 309-318. 

Among the seasonal migrants from the Mediterranean Sea, there are several species of fishes that perform seasonal feeding or spawning migrations to the Black Sea. These species refer to migrants meanwhile, they play or at least played a significant role in the trophic dynamics of the Black Sea ecosystem. 

---