Briefly, in accordance with one embodiment of the invention, a channel estimator may be adapted to provide a channel estimate based at least in part on an estimated delay spread. The methods generally involve contacting the sulfotransferase, in a reaction solution, with a sulfate donor, a test agent, and a polymeric sulfate acceptor that is readily separated from the reaction solution. The first gate electrode contains a noble gas element. The duty ratio establishing unit generates a third parameter for determining amplitude of the frequency signal generated by the PWM controller according to a reference voltage, and provides it to the PWM controller. Accordingly, it is possible to provide a ball screw which can restrict variations in the torque of the ball screw caused by the mutual sliding movements of balls occurring within a ball circulation tube. The substituted acrylic acid esters are produced by Wadsworth-Emmons olefination with trialkyl phosphonoacetate in the presence of alkali carbonate as the base, in an aqueous solvent.