A refrigerator having a lamp apparatus includes: a lamp receiving part formed at a recess portion of a rear wall surface of a storage space of the refrigerator; a light source unit installed at the lamp receiving part and being parallel to the rear wall surface of the storage space; and a lamp cover for diffusing light emitted from the light source unit. A user can quickly and conveniently select buttons. The invention further relates to a centrifugal separator using such centrifugal separator bowl. An output circuit is configured to provide an output voltage based on at least one of the first and second DC outputs. The invention also relates to processes for the preparation of the heterocyclic derivatives, to pharmaceutical compositions containing them and to their use in the manufacture of medicaments for use in the production of an antithrombotic or anticoagulant effect. A coating of polymeric material is disposed over the hop acid and at least over a portion of one of the surfaces of the layer comprising matted cellulosic fibers.