Character of magnetic excitations in a quasi-one-dimensional antiferromagnet near the quantum critical points: Impact on magnetoacoustic properties - Chiatti, O; Sytcheva, A; Wosnitza, J; Zherlitsyn, S; Zvyagin, A A; Zapf, V S; Jaime, M; Paduan-Filho, Armando (Physical Review B, 2008)