RESUMO
Application of time correlated single photon counting to pulsed Mie scattering enables one to resolve changes in light scattering to better than 50 ps. This technique is applied to the highly nonlinear motion of a sonoluminescing bubble. Physical processes, such as outgoing shock wave emission, that limit the interpretation of the data are measured with a streak camera and microscopy. Shock speeds about 6 km/s have been observed.
RESUMO
Techniques have been developed that facilitate the measurement and imaging of the charge exchanged between metal-insulator surfaces in relative motion. In the regime where the forces of friction lead to stick-slip motion, we find that the charge transfer accompanying the slip events is proportional to the force jumps and is bunched at the stick locations. The constant of proportionality is measured in electron volts per angstrom and has a small variance over a large range of slip sizes, suggesting that in these experiments macroscopic friction originates from and scales to the intrinsic electronic interactions that form between metal and insulator surfaces.
RESUMO
The dynamics of a fluid surface filled with high-amplitude ripples were studied with a technique (diffusing light photography) that resolves the height at all locations instantaneously. Even when nonlinearities are strong enough to generate a (Kolmogorov) cascade from long wavelength (where energy is input) to shorter wavelength, the resulting turbulent state contains large coherent spatial structures. The appearance of these structures in a thermal equilibrium state (with the same average energy) would be highly improbable.
