I've never heard of the "nat" until today. So I googled nat and I believe you are referring to the nursing amplitude test. If that is the case, here are a couple of sources to help you study:
http://www.personality-and-aptitude-...ng-career.html
http://abaniko.blogspot.com/2006/04/...e-test_23.html
But like I said before, make sure your school even considers that portion of the test, when evaluating their nursing student applicants. Just because the school has you take all sections of a test, doesn't mean that all sections weigh equally. I had to take all the sections of the NET (including science), but my school only looks at the scores of two sections of the test. So make sure that your school will even recognize your NAT science score. Because if they don't, that just gives you more time to study for the sections that are recognized.