Joshua Ladell (1923-2000)
J. Ladell passed away in Jerusalem, Israel, on Jan. 28, 2000. He pursued graduate studies in Physics at the Polytechnic Inst. of Brooklyn, where he received the M.S. degree in 1951 and a PhD in 1954. His dissertation was completed under I. Fankuchen. Josh was the first to attempt a least squares crystal structure refinement using the computation facilities at the IBM Watson Lab. He was awarded a Lipsky exchange fellowship to spend 1954-1956 with Gerhardt Schmidt at the Weizmann Inst. of Science in Rehovot, Israel. W. Parrish recruited him to join Philips Labs in New York. His work included studies of the geometrical optics of single crystal diffractometers, applications of crystallography to fluorescence analysis instrumentation, the theory of instrumental diffraction profiles, the development of the PAILRED automated single crystal diffractometer system, the use of dedicated microprocessors to control X-ray diffraction instruments, and the use of forbidden reflections to solve the phase problem. He developed a generalized powder diffractometer, and with co-workers published two seminal papers on the determination of surface state electronic density in thermally oxidized silicon. Josh was a dedicated scientist, crystallographer, friend and colleague.