YEAR Volume 58 (LVIII) 2013 MONTH JUNE ISSUE 1 S T U D I A UNIVERSITATIS BABE Ş –BOLYAI PHYSICA 1 Desktop Editing Office: 51 st B.P. Hasdeu, Cluj-Napoca, Romania, Phone + 40 264-40.53.52 CUPRINS – CONTENT – SOMMAIRE – INHALT B. BIRÓ, L. DĂRĂBAN, V. SIMON, Monitoring of Thermal Neutron Flux of Isotopic Sources by Activation Method ......................................................... 5 B R. DUDRIC, M. SEVER, E. DOROLTI, R. TETEAN, Preparation by High Energy Ball Milling and Magnetic Properties of Nanocrystalline La 1.4 Ca 1.6 Mn 2 O 7 Perovskite .................................................................................................... 13 A. HAPCA, L. DARABAN, Radiometric Determination of Potassium-40 in Soils by  Radiation Measurements ..................................................................... 21 I. RITI, A. VULPOI, A. URECHE, V. SIMON, Microstructural Properties of Sol- Gel Derived Bioglasses Conventionally Stabilized by Calcination Versus Repeated Immersion in Volatile Solvent ..................................................... 27 V. SIMON, D. TRANDAFIR, G. GOLLER, Synthesis and Characterization of a Novel Copper Doped SiO 2 –P 2 O 5 –B 2 O 3 -CaO–Na 2 O Glass Ceramic ................ 33