Abstract: A method for marking thin walled tubes, using a laser. To prevent warping and to maintain the structural integrity of the tube, coolant is injected into the tube while it is being marked. To further prevent warping and to maintain the structural integrity of the tube, each mark is composed of a set of relatively thin marks, each separated by an unmarked space, and the tube and the laser are moved relative to one another so that the series of marks can be generated.

Abstract: An apparatus for use in bracing or exercising a knee joint in a manner that allows bending of the joint only along a predetermined path which approximates the natural bending of the joint. On one side of the joint are upper and lower struts that run along and are attached to the upper and lower leg and are attached to one another near the joint by a connecting mechanism which includes a set of linkage arms and telescoping elements that allow the struts to pivot relative to one another along the prescribed pivot line. On the other side of the joint are other upper and lower struts that run along and are attached to the upper and lower leg and are attached to one another near the joint by a ball and socket connector. The apparatus may be used as a brace or, alternatively, may be used with a cycling mechanism to cyclically flex and extend the joint or with a force-applying mechanism to apply a constant force urging the extension or flexing of the joint.