These rates ranged from 20 to 400 "old lei" for 1 "new" leu. There have been two series of Moldovan leu banknotes. It replaced the temporary cupon currency at a rate of 1 leu = 1000 cupon. The Romanian leu has a history of instability. The most famous poet of the "trobar leu" was Bernart de Ventadorn. An internal investigation led to Bank Leu. Animals have the highest density of Leu. The bank acquired Bank Leu, known as Switzerland's oldest bank, in 1990. Half of the stock was bought by Bank Leu. On 28 January 1952, another new leu was introduced. For example, a local hydrophobicity maximum occurs in the vicinity of the invariant Leu residue. HIFAR completed conversion to low enriched uranium fuel (LEU) in 2006. The IAEA report also stated that Tehran continues to produce LEU.