Abstract: The invention relates to a lithium-rich carbonaceous substance which can be used as a negative electrode in a lithium accumulator. This substance has the following formula: LiNaxCyOz  (I) in which x, y and z are such that 0.4≦x≦0.6 2.5≦y≦3.5 0.2≦z≦1 It can be prepared by the insertion of lithium electrochemically in a graphite-sodium-oxygen compound.

Abstract: The present invention relates to a device for reducing the vibration in the cabin (2) of a rotary-wing aircraft, especially a helicopter (He).According to the invention, said device (1) comprises at least one sensor (C) arranged on the structure of the aircraft (He) and capable of measuring the values of at least one parameter that represents the vibration in said cabin (2); at least one controllable resonator (R), mounted directly in said cabin (2) and capable therein of generating a force which opposes said vibration; and a control unit (UC) capable of controlling said resonator (R) on the basis of the values measured by said sensor (C), so as to reduce and minimize said vibration.