11.   Atrial fibrillation occurs when the upper chambers of the heart quiver or beat ineffectively, instead of in a normal rhythm.

12.   Besides, the great personal power enjoyed by Democratic and Republican senators alike gives partisanship a mellower tone in the upper chamber.

13.   All children are born with a small opening between the upper chambers of their hearts.

14.   But down by only two seats in the state Senate, many Republicans say the upper chamber is their best chance at gaining a rare majority.

15.   But if the upper chamber is retained and democratically elected, how should its members be chosen?

16.   But it may be weeks or months before the upper chamber gets around to debating it.

17.   But one California congressman has not yet shut the door on a bid for the upper chamber.

18.   But now that California has sent two Democrats to the upper chamber, the Senate passed the bill in April.

19.   Compared with the House, the upper chamber should percolate as smoothly as a well-warmed coffee pot.

20.   Daschle and his party will drive legislation in the upper chamber and can sharply tilt the national agenda.