A method of operation within a data processing system that includes a plurality of processing nodes each having access to a set of shared resources. The apparatus includes a light source to produce a beam of light transmitted to a tissue via a two-way fiber optic bundle which, in one embodiment, is passed through a conventional endoscope. The control valve drives and controls the valve unit 310 by an electromagnetic force thereby adjusting an opening degree of the valve body 304. The attachment assembly permits selective positioning of the accessory assembly with respect to the vehicle whereby the accessory assembly is usable by a user. The mean radius of the tubular may be computed from multiple water path measurements around the circumference relative to a known fixture. Each of second-stage and subsequent-stage gas passages has connected to the center thereof connection holes which are provided on both ends of the previous-stage gas passages so as to be in communication with the previous-stage gas passages.