Function. Mechanical contractors are the professionals responsible for the installation of plumbing, heating, cooling, air-conditioning, refrigeration and ventilation systems.efore beginning a job, a mechanical contractor estimates in writing how long it will take to complete a particular job and how much it will cost, and then must complete all required work according to that schedule and in that price range.
In mammals, B cells mature in the bone marrow, which is at the core of most bones. In birds, B cells mature in the bursa of Fabricius, a lymphoid organ. (The B from B cells comes from the name of this organ, where it was first discovered by Chang and Glick, and not from bone marrow as commonly believed). B cells, unlike the other two classes of lymphocytes, T cells and natural killer cells, express B cell receptors (BCRs) on their cell membrane.
The B Reactor (105-B) at Hanford was the first large-scale plutonium production reactor in the world. It was designed and built by DuPont based on an experimental design by Enrico Fermi, and originally operated at 250 megawatts (thermal) .