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This study investigated the chemical composition and antimicrobial activity of propolis collected from two stingless bee species Tetragonula laeviceps and Tetrigona melanoleuca (Hymenoptera: Apidae). Six xanthones, one triterpene and one lignane were isolated from Tetragonula laeviceps propolis. Triterpenes were the main constituents in T. melanoleuca propolis. The ethanol extract and isolated compounds from T. laeviceps propolis showed a higher antibacterial activity than those of T. melanoleuca propolis as the constituent α-mangostin exhibited the strongest activity. Xanthones were found in propolis for the first time; Garcinia mangostana (Mangosteen) was the most probable plant source. In addition, this is the first report on the chemical composition and bioactivity of propolis from T. melanoleuca.

The ternary system of lead nickel niobate Pb(Ni 1/3 Nb 2/3 )O 3 (PNN), lead zinc niobate Pb(Zn 1/3 Nb 2/3 )O 3 (PZN), and lead zirconate titanate Pb(Zr 1/2 Ti 1/2 )O 3 (PZT) was investigated to determine the influence of different solid state processing conditions on dielectric and ferroelectric properties. The ceramic materials were characterized using x-ray diffraction, dielectric measurements, and hysteresis measurements. To stabilize the perovskite phase, the columbite route was utilized with a double crucible technique and excess PbO. The phase-pure perovskite phase of PNN-PZN-PZT ceramics was obtained over a wide compositional range. It was observed that for the ternary system 0.5PNN-(0.5x)PZN-xPZT, the change in the transition temperature (T m ) is approximately linear with respect to the PZT content in the range x [H11505] 0 to 0.5. With an increase in x, T m shifts up to high temperatures. Examination of the remanent polarization (P r ) revealed a significant increase with increasing x. In addition, the relative permittivity ([H9280] r ) increased as a function of x. The highest permittivities ([H9280] r [H11505] 22,000) and the highest remanent polarization (P r [H11505] 25 μC/cm 2 ) were recorded for the binary composition 0.5Pb(Ni 1/3 Nb 2/ 3 )O 3 -0.5Pb(Zr 1/2 Ti 1/2 )O 3 .The ternary system of lead nickel niobate Pb(Ni 1/3 Nb 2/3 )O 3 (PNN), lead zinc niobate Pb(Zn 1/3 Nb 2/3 )O 3 (PZN), and lead zirconate titanate Pb(Zr 1/2 Ti 1/2 )O 3 (PZT) was investigated to determine the influence of different solid state processing conditions on dielectric and ferroelectric properties. The ceramic materials were characterized using x-ray diffraction, dielectric measurements, and hysteresis measurements. To stabilize the perovskite phase, the columbite route was utilized with a double crucible technique and excess PbO. The phase-pure perovskite phase of PNN-PZN-PZT ceramics was obtained over a wide compositional range. It was observed that for the ternary system 0.5PNN-(0.5 − x)PZN-xPZT, the change in the transition temperature (T m ) is approximately linear with respect to the PZT content in the range x ‫ס‬ 0 to 0.5. With an increase in x, T m shifts up to high temperatures. Examination of the remanent polarization (P r ) revealed a significant increase with increasing x. In addition, the relative permittivity (⑀ r ) increased as a function of x. The highest permittivities (⑀ r ‫ס‬ 22,000) and the highest remanent polarization (P r ‫ס‬ 25 C/cm 2 ) were recorded for the binary composition 0.5Pb(Ni 1/3 Nb 2/3 )O 3 -0.5Pb(Zr 1/2 Ti 1/2 )O 3 .