Methods and apparatus for online fundraising may include receiving a solicited pledge. The method and apparatus are characterized in that the piezoelectric element is activated by an activation voltage having a value set as a function of manufacturing characteristics of the particular piezoelectric element and based upon, for example, a correction value for injected fuel volume. The clips are aligned when in the closed position which insures that water can drain from an upper clip through a lower clip. These reagents are capable of reacting with each other, with atmospheric air, or with other gases and fluids to generate a visible aerosol when expelled into the surrounding air. The first set of material layers and the second material layers minimize distortion of the ultrasound signals.