I'm a bit too tired to offer a substantive report on the goings-on at the FIDE Grand Prix in Zug, Switzerland; so I'll confine myself to "just the facts" comments and a few links. The last two rounds have been something of a bloodbath with three decisive games (of six) in round nine and four of six in round 10. This is at least partially due to a pretty fair number of blunders.
The most important decisive games in round 9 were Kamsky-Caruana (a well-played win for Caruana [send him back!] in a Closed Ruy and Nakamura-Morozevich (in which Morozevich self-destructed, going from much better to worse to dead lost and resigning in a game of just 34 moves; that was his third consecutive loss). After the round Topalov (who drew with Mamedyarov) still led, but by just half a point over Caruana; Ponomariov, Karjakin and Nakamura were a further half a point behind. (For further, fuller reports on the round there are plenty of options including the official site and TWIC.)
So what pairing headlined the tenth round? Caruana-Topalov, naturally. The played a Byrne Attack Najdorf that saw Topalov eschew the eponymous Topalov Variation (8...h5) with one featuring an eventual ...a5. That's not the most common approach in the Byrne Attack, and the players agreed afterwards that White had some advantage. (Though they seemed to differ about how large the advantage one - Caruana seemed more sanguine.) Topalov played the second half of the game much more accurately and incisively than Caruana, however, and managed to grind out the full point. He thus increased his lead over the field, but only to a full point rather than a point and a half. That's because Nakamura won his second straight game, and even more quickly than in round 9. Nakamura defeated Mamedyarov in just 22 moves. (There is some feeling that Mamedyarov may have resigned prematurely, but his position was clearly inferior in any case.)
Standings After Round 10:
1. Topalov 7
2. Nakamura 6
3-4. Ponomariov, Caruana 5.5
5-7. Kamsky, Karjakin, Morozevich 5
8-9. Giri, Leko 4.5
10-12. Radjabov, Mamedyarov, Kasimdzhanov 4
Final Round Pairings: