This study details the isolation, identification, and characterization of ambroxol's unknown impurity. One unknown impurity of ambroxol was formed in the formulated drug under stress conditions [40°C /75% relative humidity (RH) for 6 months] with the relative retention time (RRT) 0.68 in RP-HPLC. The impurity was enriched by exposing it to heat and it was isolated by using preparative HPLC. The...

Let K be a multivalued map from the interval [0, 1] to R. On its graph, denoted by Gr(K), another multivalued map F is defined. Its values are closed subsets of R. The map F , called an orientor field, gives rise to a differential inclusion ẋ(t) ∈ F (t, x(t)). The inclusion is called viable, if for every (t0, x0) ∈ Gr(K) there is a global absolutely continuous forward trajectory x : [t0, 1] → R...

In this article, using generalized differential quadrature (GDQ) methods, free vibration of a thin annular plate coupled with two open circuit piezoelectric layers, is numerically studied based on the classical plate theory. The governing differential equations with respective boundary conditions are derived and transformed into a set of algebraic equations by implementing the GDQ rule, then so...