The Sensex at the Bombay Stock Exchange fell 33 points, or 0.2 per cent, to 15,841 in opening trade, today, in the absence of buying by foreign funds ahead of the year-end, and amid weak Asian bourses.Later, the Sensex lost considerably more ground, and stood 140 points, or 0.9 per cent in negative territory, at 15,733 in afternoon trade.Other Asian markets in Japan, China, Hong Kong, Singapore, Indonesia, South Korea and Taiwan were down by between 0.2 percent and 1.4 percent, today, amid concerns that economic growth in the region is slowing.The US Dow Jones Industrial Average had ended flat, overnight.