Tactics

In less than a month after my first tournament there, I came back to Washington Dulles International Airport to play a second one, the 5th Continental Class Championships.  
Looking at my games after the tournament, I found that I wasn't very tactically alert.  I missed two winning opportunities in round 4 and 5.  Can you spot the winning moves here?

Black to move

White to move

Answers: 
1. Nc5 attacks the White Queen. When the Queen moves, Nb3 will win an exchange.
​2. White wins the exchange or the bishop: 1. Nb6 Rc7 2. Nd5 Rc6 3. Ne7+ Kf7 4. Nxc6 Bxc6
​or 1. Nb6 Rd8 2. Rd1