In this paper we
will (1) establish a relationship between the Turán inequalities and the
Laguerre inequalities, (2) provide a complete characterization of functions in the
Laguerre-Pólya class in terms of the Turán inequalities involving the Jensen
polynomials and (3) show that certain Hankel determinants of functions in the
Laguerre-Pólya class are nonpositive.