An on-chip circuit for defect testing with the ability to maintain a substrate voltage at a level more positive or more negative than a normal negative operating voltage level of the substrate. Adjusting the position of the balance weight inside the threaded sleeve can change the center of gravity of the putter head to meet different player’s requirements to obtain an optimum hitting stability and ball moving direction, and increase the success rate in sending the golf ball into the hole. The mail item to be stacked meets the preceding, already stacked item at an acute angle. The invention further provides a bone xenograft for implantation into a human including a portion of a bone from a nonhuman animal, wherein the portion has substantially no surface carbohydrate moieties which are susceptible to glycosidase digestion. In some embodiments, the luminescent material structure is between about 15 and about 100 microns thick. A biasing agent such as a spring presses the pulleys toward the drum by urging the yoke toward the pulley.