Macroscopic spreading kinetics

Fig. 3. Spreading kinetics of the macroscopic part of the drops, characterized by their size R and their apparent contact angle 0, for a wide range of drop characteristics, and two spreading parameter values.

All of the other phenomena associated with waves can also be observed in particles. For example, in 1927 Davisson and Germer accelerated a beam of electrons to a known kinetic energy and showed that these electrons could be diffracted off a nickel crystal, just as X-rays are diffracted (see Figure 3.8). Just as with photons, interference is not always seen if the wavelength spread or the slits are large, the fringes wash out. This also explains why interference is not seen with macroscopic objects, such as buckshot—the wavelength is far too small. 

Kinetic regime. The first mechanism corresponds to the so-called kinetic regime (Popel 1994, Grigorenko et al. 1998) which is similar to the adsorption/desorption model (Blake 1993). Contrary to macroscopic hydrodynamic models, the adsorption/desorption model is based on the hypothesis that the motion of the triple line is ultimately determined by the statistical kinetics of atomic or molecular events occurring within the three-phase zone (Samsonov and Muravyev 1998). Such processes may be limiting at the very early stages of spreading of low... 

The 19th century saw numerous extensions of the atomic theory, one of the most important being the kinetic theory of gases. The macroscopic behavior of gases may be explained by considering them to be composed of molecules in rapid random motion, with characteristic speeds of the order of several hundred meters per second (m/s). The continual collisions of the highspeed molecules with the walls constitute the pressure exerted by the gas on a container. The molecules exhibit a characteristic statistical spread of velocities, known as the Maxwell-Boltzmann distribution, which will be discussed in detail in a later chapter because of its relevance to the physics of neutrons in a scattering medium such as a reactor lattice. 

---