How to remind a professor about an old email I sent to him?

I have applied to 4 PhD applications in Computer Science and I have sent an introduction email to a professor in each of the schools I have applied to. In this email I first introduced myself and then mentioned one of their papers I'm interested in, and at the end asked them for any time they can give me to meet them in person and talk to them about my future plans. But, I just heard from one professor and the rest have not replied my email after two weeks. How could I write an email to remind them about my old email I sent them? I googled and did not find a concise answer. Any help is appreciated.