I'm a bit new to cycles shaders, so I'm going about this a bit blindly.
I've tried mixing a few shaders, and it works in the rendered viewport, but not in the full render.
I'm trying to make spaceship thrusters. It should start emitting brightly, and then gradually fade to transparent. I've tried both particles, and volumes, but neither worked well for me.
This is my material:
And here is the (expected) 3D View rendered result (left) and the actual (incorrect) rendered result (right):
EDIT: I was able to get it to work by switching to CPU from GPU.