Abstract: Acicular magnetic iron oxide particles comprise:acicular magnetite particles having 10 to 24% by weight of ferrous as core particles;a magnetite coating which is formed on the surfaces of said acicular magnetite particles by epitaxial growth and which has maghemite at least in a part of the surface of said magnetite coating; anda cobalt-containing oxide layer which is formed on said magnetite coating and which contains cobalt of 1.5 to 2.5 wt % based on the total weight of said acicular magnetic iron oxide particles.

Abstract: A scroll type fluid apparatus, such as a scroll vacuum pump or a scroll compressor, does not require lubrication by an external lubricating device. The scroll type fluid apparatus includes a casing, a stationary scroll member fixed to the casing, an orbiting scroll member cooperating with the stationary scroll member to form sealed chambers therebetween, and a restraining mechanism for restraining the orbiting scroll member from rotating about its own axis. The restraining mechanism employs prelubricated sealed bearings which support its component parts so that the component parts are in rolling contact with the corresponding portions of the orbiting scroll member, so that the component parts and the corresponding portions of the orbiting scroll member are not radially abraded, and portions of the scroll type fluid apparatus exposed to the fluid need not be lubricated by an external lubricating device.

Abstract: A vacuum pump includes a rotary vacuum pump including a pair of rotors cooperating to suck gas, a driving source connected to a shaft of one of the pair of rotors, timing gears connected to respective shafts of the rotors and transmitting the driving force of the driving source between the shafts of the pair rotors, and a reciprocating vacuum pump connected to the driving source and connected to the downstream side of the rotary vacuum pump for sucking gas therefrom.