1. NITROGEN ISOTOPE EXCHANGE BETWEEN NITRIC OXIDE AND NITRIC ACID. Authors: D. AXENTE.2. ASPECTS REGARDING COMPUTER CONTROL OF 15N SEPARATION PLANT. Authors: M. KAUCSÁR, V. COSMA, D. AXENTE, A. BÂLDEA, H. BENDEA, V. BUNEA.3. SYNTHESIS OF [1, 3 - 15N2] URACIL. Authors: D. AXENTE, MARIA CHIRIAC.