Tendon the Achilles tendon stretches as the ankle joint dorsiflexes. During the last portion of the stride, as the foot plantar-flexes (pointing the toes down), the stored elastic energy is released. Furthermore, because the tendon stretches, the muscle is able to function with less or even no change in length, allowing the muscle to generate greater force. The mechanical properties of the tendon are dependent on the collagen fiber diameter and orientation. The collagen fibrils are parallel to each other and closely packed, but show a wave-like appearance due to planar undulations, or crimps, on a scale of several micrometers. In
Inelastic scattering collisions often transfer kinetic energy between particles, scattering due to elastic collisions can also be "in"elastic, as in Compton scattering. When an electron is the incident particle, the probability of inelastic scattering, depending on the energy of the incident electron, is usually smaller than that of elastic scattering. Thus in the case of gas electron diffraction, reflection high-energy electron diffraction (RHEED), and transmission electron diffraction, because the energy of the incident electron is high, the contribution of inelastic electron scattering can be ignored. Deep inelastic scattering of electrons from protons provided the first direct evidence for the existence of quarks.