The third edition's major areas are presided over by the following executive board members: Stephen Hawking (astronomy, astrophysics, mathematics); Daniel Goldin and Herbert Friedman (space sciences); Paul Crutzen (atmospheric science); Yuan Lee, George Olah, Elias Corey, and Allen Bard (chemistry); R. A. Mashelkar (chemical engineering); Melvin Schwartz, Ludwig Faddeev and Klaus von Klitzing (physics); Edward Teller (nuclear technology); Frederick Seitz (environment); Benoit Mandelbrot (mathematics); Aaron Klug (molecular biology and biotechnology); Philip Sharp (molecular and cell biology); John Bollinger, Karl Pister, and Gordon Slemon (engineering); Michael Buckland (library sciences); and Jean Carpentier (aerospace sciences). Approximately 200 articles have been deleted from the second edition, 300 added, and 480 updated or rewritten. Areas new to this edition are molecular electronics, nanostructured materials, image-guided surgery, fiber-optic chemical sensors, metabolic engineering, self-organizing systems, tissue engineering, humanoid robots, gravitational wave physics, pharmacokinetics, thermoeconomics, and superstring theory. A thousand authors prepared entries running approximately 17-18 pages each. Each article features a table of contents, glossary, related entries, and a bibliography. A separate reference volume—the Encyclopedia's gateway—provides an alphabetical list of entries, subject index, and a valuable index providing a compendium of entries related to each other.