You would use "there is no" when you are referring to an object without putting an article (a, an, or the) before the object. For example: There is no way to get around that boulder. You are referring to "way," but you did not put "a," "an," or "the" in front of it. You would use "there is not" when you are referring to an object and you DO put an article before the object. For example: There is not a way to get around that boulder. You are still referring to "way," but you have used the article "a" in front of it. I really hope I was able to help. :)