The forces of interaction (attraction and repulsion) depend not only on the properties of the bodies in contact and the layer separating these, but also on the external applied force. This force determines the thickness of the gap between the bodies. If the compressing force is no greater than Fj ax (height of the force barrier) the adhesive force will be relatively small and equal to F nin H the compressive force exceeds F the adhesive force will be equal to F nin [Pg.127]

Figure 7. Three possible interactions (.attractive and repulsive) between phases in multiple emulsions are shown in the upper diagram, while below those arrangements of the aqueous (W), surfactant (s and Sg) and oil phases are shown which must be taken into account in calculation of attractive and repulsive forces in these interactions. |

The first term includes the electrostatic attractions and repulsions between the net charges on pairs of atoms, one from each molecule. The second involves interactions between occupied and vacant molecular orbitals on the two molecules. The hypothesis is that the reaction proceeds in a way to produce the most favorable [Pg.139]

Again, we are reminded that Nature provides the ultimate model for emulation in the use of cooperative interactions of an enormous number of small structural components through many weak, reversible attractions and repulsions to produce such complex microstructures as proteins, enzymes, viruses, and cells with virtually perfect fidelity (Whitesides, 1991). One important strategy for producing ultra-thin films of promise for microelectronics [Pg.46]

Figure 7.10. Distribution of two adsorbates A and B over a surface with different combinations of attractive and repulsive interactions, as predicted by a Monte Carlo simulation. (Courtesy A.P. van Bavel, Eindhoven.) |

The DLVO theory is a theoretical construct that has been able to explain many experimental data in at least a semiquantitative manner it illustrates plausibly that at least two types of interactions (attraction and repulsion) are needed to account for the overall interaction energy as a function of distance between the particles. [Pg.871]

When the two atoms are relatively far apart, there is essentially no interaction at all between them both the attractive and repulsive forces are about zero. As the two atoms get closer, the attractive forces dominate, and the potential energy decreases to a minimum at a distance of 0.74 A, which is the H-H bond length. At distances less than 0.74 A, the repulsive forces become more important and the energy increases sharply. [Pg.105]

P/100, surface coverage / , AG/2.303 RT AC, free energy of adsorption R, gas constant T, temperature c, bulk inhibitor concentration n, number of water molecules replaced per inhibitor molecule f, inhibitor interaction parameter (0, no interaction + attraction and repulsion) K, constant and % P = 1 inhibited corrosion rate/uninhibited corrosion rate. [Pg.84]

These two complementary mles are intuitively obvious, e.g. can be simply derived by considering the lateral attractive and repulsive interactions of coadsorbed reactants and promoters as already shown in section 4.5.9.2. They can explain all the observed promotionally induced kinetics for more than sixty different catalytic systems (Table 6.1). As an example these two rules can explain all the observed changes in kinetics orders with

The interactions between similar particles, dissimilar particles, and the dispersion medium constitute a complex but essential part of dispersion technology. Such interparticle interactions include both attractive and repulsive forces. These forces depend upon the nature, size, and orientation of the species, as well as on the distance of separation between and among the particles of the dispersed phase and the dispersion medium, respectively. The balance between these forces determines the overall characteristics of the system. [Pg.247]

The interaction between atoms separated by more than two bonds is described in terms of potentials that represent non-bonded or Van der Waals interaction. A variety of potentials are being used, but all of them correspond to attractive and repulsive components balanced to produce a minimum at an interatomic distance corresponding to the sum of the Van der Waals radii, V b = R — A. The attractive component may be viewed as a dispersive interaction between induced dipoles, A = c/r -. The repulsive component is often modelled in terms of either a Lennard-Jones potential, R = a/rlj2, or Buckingham potential R = aexp(—6r ). [Pg.403]

The discussion thus far has focused on the forces between an array of atoms connected together through covalent bonds and their angles. Important interactions occur between atoms not directly bonded together. The theoretical explanation for attractive and repulsive forces for nonbonded atoms i and j is based on electron distributions. The motion of electrons about a nucleus creates instantaneous dipoles. The instantaneous dipoles on atom i induce dipoles of opposite polarity on atom j. The interactions between the instantaneous dipole on atom i with the induced instantaneous dipole on atom j of the two electron clouds of nonbonded atoms are responsible for attractive interactions. The attractive interactions are know as London Dispersion forces,70 which are related to r 6, where r is the distance between nonbonded atoms i and j. As the two electron clouds of nonbonded atoms i and j approach one another, they start to overlap. There is a point where electron-electron and nuclear-nuclear repulsion of like charges overwhelms the London Dispersion forces.33 The repulsive [Pg.44]

As the distance between the two particles varies, they are subject to these long-range r " attractive forces (which some authors refer to collectively as van der Waals forces). Upon very close approach they will experience a repulsive force due to electron-electron repulsion. This repulsive interaction is not theoretically well characterized, and it is usually approximated by an empirical reciprocal power of distance of separation. The net potential energy is then a balance of the attractive and repulsive components, often described by Eq. (8-16), the Lennard-Jones 6-12 potential. [Pg.393]

If the substituents are nonpolar, such as an alkyl or aryl group, the control is exerted mainly by steric effects. In particular, for a-substituted aldehydes, the Felkin TS model can be taken as the starting point for analysis, in combination with the cyclic TS. (See Section 2.4.1.3, Part A to review the Felkin model.) The analysis and prediction of the direction of the preferred reaction depends on the same principles as for simple diastereoselectivity and are done by consideration of the attractive and repulsive interactions in the presumed TS. In the Felkin model for nucleophilic addition to carbonyl centers the larger a-substituent is aligned anti to the approaching enolate and yields the 3,4-syn product. If reaction occurs by an alternative approach, the stereochemistry is reversed, and this is called an anti-Felkin approach. [Pg.90]

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