Abstract: Devices and methods for node traversal for ray tracing are provided, which comprise casting a first ray in a space comprising objects represented by geometric shapes, traversing, for the first ray, at least one first node of an accelerated hierarchy structure representing an approximate volume of a group of the geometric shapes and a second node representing a volume of one of the geometric shapes, casting a second ray in the space, selecting, for the second ray, a starting node of traversal based on locations of intersection of the first ray and the second ray and an identifier which identifies one or more nodes intersected by the first ray and traversing, for the second ray, the accelerated hierarchy structure beginning at the starting node of traversal.

Abstract: The compound 6-.beta.-chloropenicillanic acid can be prepared in substantially pure form and is a .beta.-lactamase inhibitor which may be used to enhance the effectiveness of penicillins acid cephalosporins against .beta.-lactamase producing lacteria.The process comprises the reaction of a compound of the formula: ##STR1## wherein R.sup.X is hydrogen or a carboxyl-blocking group and R is an aryl group, with a trialkyl tin hydride or a triaryl tin hydride or a dialkyl tin dihydride and optionally removing any carboxyl-blocking group R.sup.X, and/or oxidizing the atoms to an SO or SO.sub.2 ; and/or esterifying a salt of the acid to yield an in-vivo hydrolysable ester.