Influence of uniaxial tensile stress on the mechanical and piezoelectric properties of short-period ferroelectric superlattice

Tetragonal ferroelectric/ferroelectric BaTiO3/PbTiO3 superlattice under uniaxial tensile stress along the c axis is investigated from first principles. We show that the calculated ideal tensile strength is 6.85 GPa and that the superlattice under the loading of uniaxial tensile stress becomes soft along the nonpolar axes. We also find that the appropriately applied uniaxial tensile stress can significantly enhance the piezoelectricity for the superlattice, with piezoelectric coefficient d33 increasing from the ground state value by a factor of about 8, reaching 678.42 pC/N. The underlying mechanism for the enhancement of piezoelectricity is discussed

Life Cycle and Survival of Hyalomma dromedarii (Acari:Ixodidae) Under Laboratory Conditions

The life cycle of Hyalomma dromedarii Koch (Acari:Ixodidae) on rabbits at 25 and 32ºC was compared at 85% R.H. At these temperatures, it behaved as a two-host tick and completed its life cycle in 108-146 and 80-115 days, respectively. The preoviposition, incubation and moulting periods varied significantly and were influenced by temperature. The survival periods of different developmental stages of Hyalomma dromedarii at 25ºC, 32, 38, 43, and 48ºC at 85% R.H. were investigated. The eggs, engorged nymphs and engorged females died at 38ºC, and the unfed larvae died at 43ºC. The longevity of the unfed adults decreased from 90-120 days at 25ºC to7-15 days at 43ºC. They died at 48ºC. These results suggest that the survival periods of eggs, engorged nymphs and engorged females were significantly decreased with an increase in temperature. They were more susceptible to high temperature than unfed adults. The role of unfed adult in the continuity of the life cycle of the tick throughout the year is discussed.

Life Cycle and Survival of Hyalomma dromedarii (Acari:Ixodidae) Under Laboratory Conditions

The life cycle of Hyalomma dromedarii Koch (Acari:Ixodidae) on rabbits at 25 and 32ºC was compared at 85% R.H. At these temperatures, it behaved as a two-host tick and completed its life cycle in 108-146 and 80-115 days, respectively. The preoviposition, incubation and moulting periods varied significantly and were influenced by temperature. The survival periods of different developmental stages of Hyalomma dromedarii at 25ºC, 32, 38, 43, and 48ºC at 85% R.H. were investigated. The eggs, engorged nymphs and engorged females died at 38ºC, and the unfed larvae died at 43ºC. The longevity of the unfed adults decreased from 90-120 days at 25ºC to7-15 days at 43ºC. They died at 48ºC. These results suggest that the survival periods of eggs, engorged nymphs and engorged females were significantly decreased with an increase in temperature. They were more susceptible to high temperature than unfed adults. The role of unfed adult in the continuity of the life cycle of the tick throughout the year is discussed