An apparatus and method that effects selectable width of a roller track conveyance system having multiple roller tracks with asymmetric wall heights. The catalyst becomes spent as deposits from the reaction clog up pores on the catalyst surface. When using supertwist nematic or twisted nematic liquid crystals, a reflector can be used that comprises a selective color reflector. Whether the patient is currently experiencing or anticipated to experience gait freeze caused by their neurological disorder, such as Parkinson’s disease, may also be determined. The tool carriages are spaced from each other providing non-machining access durations wherein the workpiece may be loaded or unloaded from its rotating support spindles.