Maintaining the downward trend, the Sensex at the Bombay Stock Exchange was trading 42 points in the negative zone at 17,636 in afternoon trade, a short while ago. After losing 104 points yesterday, the 30-share barometer fell by 14 points in opening trade today, as participants trimmed positions, amid a weak trend in Asia.The Nifty at the National Stock Exchange was trading 18 points in the red at 5,333.