Let and be commutative rings with unity, a ring homomorphism and an ideal of . Then the subring and of is called the amalgamation of with along with respect to . In this paper, we determine when is a (generalized) filter ring.
We characterize the postulation character of arithmetically Gorenstein curves in P4. We give conditions under which the curve can be realized in the form mH - K on some ACM surface. Finally, we complement a theorem by Watanabe by showing that any general arithmetically Gorenstein curve in P4 with arbitrary fixed postulation character can be obtained from a line by a series of ascending complete-intersection biliaisons.