A magnet assembly has a field shaping device that is cylindrically symmetric with respect to the z-axis and made of magnetic material. The temperature difference at such locations is determined and the blood flow is calculated as a function of the change in energy level and of the temperature differences measured prior to and following the change in energy level. The ultraviolet light bulb preferably includes a casing for holding a starting gas and a vaporizable material, and at least one electrode electrically coupled to the power source for exciting the starting gas and the vaporizable material within the casing. Also, a method of non-stochastically producing a library of chimeric nucleic acid molecules having an overall assembly order that is chosen by design.