fluorescence chemical sensors for the highly sensitive and selective determination of pb2+ , hg2+, co2+ and fe3+ ions in aqueous solutions are described. the ion sensing system was prepared by incorporating lipophilic ligand (l) as a neutral ion-selective fluoroionophore in the plasticized pvc membrane containing sodium tetraphenylborate or potasium tetrakis (p-chlorophenyl) borate as a liphoph...

While technical efficiencies of firms that are estimated with respect to a given frontier are comparable, this is not normally valid the case among firms that operate under different technologies. Such problem arises when comparisons of firms from different regions of country are involved. This study uses the concept of the metafrontier function to investigate regional differences in milk produ...