Usd/maj. - Janet Yellen, President of the San Francisco Fed, said the recent sharp rise in U.S. Treasury yields wud be 'disconcerting' if it is driven by worries that the Federal Reserve will not be able to prevent a jump in inflation. Yellen warned that more volatility could lie ahead of U.S. and global economies now that a long period of relative stability, often termed the 'Great Moderation', seened to have passed.