A simple example of a set which is dense-in-itself but not closed (and hence not a perfect set) is the subset of irrational numbers. This set is dense-in-itself because every neighborhood of an irrational number contains at least one other irrational number . On the other hand, this set of irrationals is not closed because every rational number lies in its closure. For similar reasons, the set of rational numbers is also dense-in-itself but not closed.
Scientists at University of Western Australia, Center for Child Health Research publish new data on life sciences in children.
Apr 06, 2009; Investigators publish new data in the report 'Need to establish a national diagnostic capacity for foetal alcohol spectrum...