New style emergency exits

After spending about 10 hour in the exit rows of aluminum tubes over the
last week I noticed something new. They 737-800 has a different design
than the older style overwing hatches. This is more door like. It has
hinges and opens outward. You no longer have to bring the door in and
throw it out of the hole you just created.

Two thoughts: First: for purposes of getting out of the airplane this is
better. If you have people piled up behind you getting the hatch into
the airplane would be more difficult. Problem solved.

Second: What is keeping a nut from trying to open the door in flight?
How does this system work? Do they have an evacuate button in the
cockpit that releases any locks on the overwing exit? Ok so what powers
it if you loose all generating capacity? or is there a pressure
sensitive lock on the door?

Just wondering.....
Michelle