Contact distance, definition

The best way to combine all these parameters is to trace back the catalytic action of enzymes to intramolecularity. It is generally accepted that when van der Waals distances (contact distances) are imposed for definite times upon reactive groups, intramolecular reactions occur then at enzyme-like rates (accelerations of 10 to 10 0 are associated to enzyme-catalysed reactions). On the other hand, according to the Page-Jencks theory [17] the fast rates of intramolecular reaction "are merely an entropic consequence of converting a bimolecular reaction into a unimolecular reaction". 

Table 5 Carbon-carbon intramolecular through space contact distance, (A), between overlapping carbons (see text for definition) and smallest contact distances for each molecule...

An ion adsorbed on the surface of a suspension will draw near to it an ion of opposite sign in the solution these ions in the double layer are thus hound and can only escape if their kinetic energy exceeds a definite critical value W. If the chemically adsorbed ions have a valency % and n is the valency of the opposite charged ions in the liquid of dielectric constant K in contact with the solid and separated from the former by a distance x, we obtain... 

Atoms in crystals cannot be regarded as scattering points the diameter of the electron cloud of an atom is of the same order of size as the distance between the centres of adjacent atoms—in fact, to a first approximation, the atoms in many crystals may be regarded as spheres of definite radius in contact with each other the electron clouds... 

The interpretation of this quantity is the following consider a photon, or any massless particle, which travels along the direction. By definition the line element for such a particle is null, therefore one has drj = d -. Since there is a correspondence between p and t through Eq. (7.6), Ar/ can therefore be seen as the maximal distance that can be traveled by any particle between time /,i(//) and taiv + Ar/). When r/ varies from — oo to some finite value today, any observer has been in causal contact with any observer in the past. On the contrary, if p has varied between two finite values, then only a fine region of the Universe has been in contact with the observer. Equivalently if asymptotically p goes to infinity, an observer can send signal to any observer, whereas if p reaches a finite value in the future, only a finite set of observer can receive... 

Almost by definition, an electronic device has at least two contacts. Here we consider a single one therefore, it is assumed that the bulk conductivity of the material and the distance between contacts are large enough, so that over most of that distance the material s energy levels are not influenced by the contacts. This is not true in the case of space-charge-limited currents [215], especially in double injection, a situation that may occur in CP LEDs (see Section V.C). 

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