looping through authors

Two questions:
1: What is the correct way of looping through authors where they
published or not published articles in a particular section/rubrique,
and list the name if authors. For example, I want to list authors who
have not published articles in section/rubrique 2.
2: How do I sort authors who have published more than for example 10
articles, and list their names?
Thank you

PS: I read the following article, but it doesn't help me.