Ceyx, a developer of laser control systems for optical communications networks, has moved its corporate headquarters to 3645 Ruffin Road, Ste. 101, San Diego, CA 92123. The company also said it has raised $4.5 million in venture funding. Ceyx unveiled its SLC real-time ER and OMA control system at the Optical Fiber Conference last month in Anaheim.    . . .   JP Sercel Associates (JPSA) announced it has appointed BUA International Ltd. to represent its line of ultraviolet (UV) laser processing systems and job shop services in Ireland. Eddie Hawkins is BUA's respresentative there. JPSA, of Hollis, N.H., makes laser micromachining and laser beam delivery systems and provides UV laser materials processing development, optical damage testing and excimer laser refurbishment services. BUA International is based in Meath, Ireland.    . . .   Nonlinear Dynamics Ltd., a UK-based provider of analysis and data mining tools for bioinformatic applications, including ellectrophoresis gels and microarrays, has announced an OEM partnership with PerkinElmer Inc., a Wellesley, Mass., provider of drug discovery, life science research and analytical solutions. PerkinElmer will distribute Nonlinear's 1-D, 2-D and array software, and Nonlinear will be PerkinElmer's principal software partner for all proteomics applications.    . . .    Siemens Medical Solutions, based in Malvern, Mass., collaborated with Massachusetts General Hospital (MGH) to develop a prototype area-detector-based, volume computed tomography (CT) system. The system was developed on a Siemens Somatom Sensation CT gantry and uses 2-D digital flat-panel detector technology. Potential applications of volumetric CT scanning are being evaluated at MGH with the prototype system, which could offer a unique window on human anatomy and physiology, Siemens said. For example, using volume CT, a medical professional could directly visualize the trabecular structure of bone, dynamic contrast uptake of tumor tissue, composition of atherosclerotic plaque in the vascular system and coronary arteries and microcirculation of the cardiac muscle. The prototype was designed for in-vitro imaging of specimens as well as in-vivo imaging of large animals and eventually human research.