The Robotic Multiobject Focal Plane System of the Dark Energy Spectroscopic Instrument (DESI)

A system of 5020 robotic fiber positioners was installed in 2019 on the Mayall Telescope, at Kitt Peak National Observatory. The robots automatically retarget their optical fibers every 10-20 minutes, each to a precision of several microns, with a reconfiguration time of fewer than 2 minutes. Over the next 5 yr, they will enable the newly constructed Dark Energy Spectroscopic Instrument (DESI) to measure the spectra of 35 million galaxies and quasars. DESI will produce the largest 3D map of the universe to date and measure the expansion history of the cosmos. In addition to the 5020 robotic positioners and optical fibers, DESI’s Focal Plane System includes six guide cameras, four wave front cameras, 123 fiducial point sources, and a metrology camera mounted at the primary mirror. The system also includes associated structural, thermal, and electrical systems. In all, it contains over 675,000 individual parts. We discuss the design, construction, quality control, and integration of all these components. We include a summary of the key requirements, the review and acceptance process, on-sky validations of requirements, and lessons learned for future multiobject, fiber-fed spectrographs

Total elbow replacement: outcome of 1,146 arthroplasties from the Scottish Arthroplasty Project

BACKGROUND AND PURPOSE: Total elbow replacement (TER) is used in the treatment of inflammatory arthropathy, osteoarthritis, and posttraumatic arthrosis, or as the primary management for distal humeral fractures. We determined the annual incidence of TER over an 18-year period. We also examined the effect of surgeon volume on implant survivorship and the rate of systemic and joint-specific complications. METHODOLOGY: We examined a national arthroplasty register and used linkage with national hospital episode statistics, and population and mortality data to determine the incidence of complications and implant survivorship. RESULTS: There were 1,146 primary TER procedures (incidence: 1.4 per 10(5) population per year). The peak incidence was seen in the eighth decade and TER was most often performed in females (F:M ratio = 2.9:1). The primary indications for surgery were inflammatory arthropathy (79%), osteoarthritis (9%), and trauma (12%). The incidence of TER fell over the period (r = –0.49; p = 0.037). This may be due to a fall in the number of procedures performed for inflammatory arthropathy (p < 0.001). The overall 10-year survivorship was 90%. Implant survival was better if the surgeon performed more than 10 cases per year. INTERPRETATION: The prevalence of TER has fallen over 18 years, and implant survival rates are better in surgeons who perform more than 10 cases per year. A strong argument can be made for a managed clinic network for total elbow arthroplasty