Polonium initiator was classified until the 1960s. The Atomic Energy Commission and the Manhattan Project funded human experiments using polonium on five people at the University of Rochester between 1943 and 1947. The people were administered between of polonium to study its excretion. Polonium is a very rare element in nature because of the short half-life of all its isotopes. Po, Po, and Po appear in the decay chain of U; thus polonium can be found in uranium ores at about 0.1 mg per metric ton (1 part in 10), which is approximately 0.2% of the abundance of radium. The amounts
Discover Card card was used. A 1989 study found that Discover had strong consumer adoption in the U.S.; the number of households with Discover cards increased by 2.1 million, or 14 percent, in 1989. Discover was also noteworthy for being the only credit card accepted by the U.S. Customs Service to pay customs duty, effective Feb. 19, 1987. Since it did not charge a percentage fee to retailers, unlike Visa, MasterCard, and American Express, Discover was also the only credit card accepted at Sam's Club; the retailer has since started to accept MasterCard and American Express (see below). The plan to create