A method of operating an electrostatic precipitator comprises feeding the precipitator with electric power generated by a power supply according to a regime adapted to impart between the precipitator electrodes a voltage having a DC components and an AC component. Individuals at a high risk of developing or having hypercholesterolemia and atherosclerosis may be treated with an effective dose of a composition comprising at least one citrus flavonoid, at least one tocotrienol, and at least one phytosterol or phytosterol ester. The notch has a concave edge formed continuously with the convex edge. The plurality of holes may include three holes along a side border of the sheet. The invention also relates to a gripper for using in said method. The communication system uses normal wireless handsets or other mobile or fixed stations without need for any modifications.