Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Colors code the three discriminability levels: red, green and blue for 
and 
pixel(s) difference respectively. Symbols denote data (see text for details) and solid curves denote the delayed exponential fit.
