Disclosed are a method and a system of sharing resources between operators in cellular mobile communication networks, wherein each operator comprises its own dedicated resource. Lubricating grease is sealed in the bearing in an amount of not less than 20% of an entire spatial volume of an interior of the rolling bearing and not more than 80% of a stationary spatial volume of the interior of the rolling bearing. The ultrasonic transducer elements are respectively disposed at the openings on a first surface of the substrate. A related method is also disclosed. It also relates to the compounds as such and to mesogenic or liquid crystalline mixtures comprising these compounds.