sentences:  One of Theodorsen's first activities was the invention of an instrument for detecting buried metals and on its first use it located a live bomb.The ensuing years were highly productive ones for Theodorsen in a number of experimental and theoretical areas.Theodorsen improved thin airfoil theory by introducing the angle of best streamlining, developed the now classical and elegant theory of arbitrary wing sections, performed the first in-house noise research, worked on fire prevention in aircraft and on means of icing removal and prevention, contributed to the theory of open, closed and partially open wind-tunnel test sections, developed the basic theory of aircraft flutter and its verification, made early measurements of skin friction at transonic and supersonic speeds, developed the use of freon for experimental aeroelastic work, gave damping properties of structures and expanded general propeller theory.