Tin sources and trade in ancient times Bantu culture of Zimbabwe are known to have actively mined, smelted and traded tin between the 11th and 15th centuries AD . Tin deposits exist in many parts of South America, with minor deposits in southern Peru, Colombia, Brazil, and northwestern Argentina, and major deposits of exploitable cassiterite in northern Bolivia. These deposits were exploited as early as 1000 AD in the manufacture of tin bronze by Andean cultures, including the later Inca Empire, which considered tin bronze the "imperial alloy". In North America, the only known exploitable source of tin during ancient times is located in the Zacatecas tin
Antimicrobial copper-alloy touch surfaces contract, which is ongoing, will also evaluate the effectiveness of copper alloy touch surfaces to prevent the transfer of microbes to patients and the transfer of microbes from patients to touch surfaces, as well as the potential efficiency of copper-alloy based components to improve indoor air quality. The latest results from the studies at the three institutions will be developed into a manuscript for publication. In a separate initiative not funded by the U.S. Department of Defense, clinical trials at an infectious disease outpatient ward consisting of patients with HIV and other infectious diseases are being conducted at North Shore