Eneigy barrier

The stabilization of an emulsion involves slowing the destabilization, primarily the flocculation process. This may be achieved in two principal manners by reducing the mobility of droplets through enhanced viscosity or by inserting an eneigy barrier between them (see also DISPERSANTS FLOCCULATING AGENTS). 

Energy Barrier. An eneigy barrier results in repulsive forces between droplets when they approach each other. The half-life of an emulsion changes drastically when eneigy barriers of different height are introduced in the system. Increasing the barrier to 20 kT gives a typical half-life of a few years which is sufficient for most applications. 

TABLE 8. Values of the length (A) of the forming C—C bonds (1 ) and of the eneigy barrier (A ) (in kcal mol ) for the conceited transition state of the butadiene - -ethylene reaction computed at several levels of calculation s... 

The coagulation occurs when the particles approach on the distance corresponding to the first minimum energy, sometimes to the second minimum The approach of particles is hampered by the eneigy barrier, dependent on their size and surface... 

Sancho M, Partenskii MB, Donnan V, Jordan PC (1995) Extended dipolar chain Model for ion channels electrostriction effects and the translational eneigy barrier. Biophys. J 68 427-433 SannerMF, Olson AJ, Spehner J-C (1996) Reduced surface an efficient way to compute molecular surfaces. Biopolymers 38 305-320... 

The blocking temperature characterizes the eneigy barrier resulting from magnetic anisotropy and that is in the way of the magnetic moment of the cluster turning into the direction of the magnetic field. 

Of special interest are the eneigy barriers for given reactions, and in principle, calculation of the potential eneigy surfaces can provide these quantities. In practice, the majority of studies report one-point calculations on SCF-minimized geometries. Generally, calculations for gas-phase Sj 2 reactions use the model dqncted for the identity reaction ... 

The eneigy barrier for this pseudorotation process, which most probably has a C4 symmetrical transition state, is in the range of AG = 13-14 kcal mol. A similar molecular motion (with a much lower energy barrier) was already assumed from relaxation time studies for the corresponding derivatives of t-butylcalix[4]arene [41]. 

Tables 1 and 2 give MM3 and MM3 calculations (carried out with MacroModel 5.5 and MM3 (94), respectively) for bond lengths and eneigy barriers involving conjugated molecules.

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