While at Varian, Dr. Hyde and his colleagues extended the technique of electron nuclear double resonance (ENDOR), which had been introduced by G. Feher for the study of donors in silicon, to the liquid phase, to unordered solids, to flavoproteins and to copper proteins. He introduced the technique of electron-electron double resonance (ELDOR) for the study of spectral connectivity in fluids.[9] He discovered a way to measure very slow rotational diffusion of proteins, and also introduced the EPR pulse technique known as saturation recovery for the measurement of electron spin lattice relaxation times of free radicals and spin labels in the fluid phase. At MCW, a key advance was a novel sample-containing structure which became known as the loop-gap resonator (LGR). It was an enabling structure for the extension of EPR spectroscopy to a range of microwave frequencies from 500 MHz to 140 GHz. In addition, the technique of saturation recovery was further developed across most of this range of microwave frequencies, which led to an extensive body of work on transport and cellular consumption of oxygen.Pulse experiments on oxygen transport at 90 GHz are particularly notable because of the small sample volume, about 20 nL.