A newly synthesized alkyl phosphinic acid resin (APAR) was used for on-line preconcentration of trace rare earth elements (REES, lanthanides including yttrium) and then determined by inductively coupled plasma mass spectrometry. REEs in seawater could be on-line concentrated on the APAR packed column (4.6mm i.d.x50mm in length), and eluted from the column with 0.5mL 0.1molL(-1) nitric acid with...

In this paper we provide several new results concerning word and matrix semigroup problems using counter automaton models. As a main result, we prove a new version of Post’s correspondence problem to be undecidable and show its application to matrix semigroup problems, such as Any Diagonal Matrix Problem and Recurrent Matrix Problem. We also use infinite periodic traces in counter automaton mod...