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Gamma-ray bursts (GRBs) are the most intense explosions in the Universe. GRBs with extended emission (GRBs EE) constitute a small subclass of GRBs. GRBs EE are divided into EE-I GRBs and EE-II GRBs, according to the Amati empirical relationship rather than duration. We test here if these two types of GRB have different origins based on their luminosity function (and formation rate). Therefore, we use Lynden-Bell's c − method to investigate the luminosity function and formation rate of GRBs with EE without any assumption. We calculate the formation rate of two types of GRBs. For EE-I GRBs, the fitting function can be written as ρ(z) ∝ (1 + z)−0.34 ± 0.04 for z < 2.39 and ρ(z) ∝ (1 + z)−2.34 ± 0.24 for z > 2.39. The formation rate of EE-II can describe as ρ(z) ∝ (1 + z)−1.05 ± 1.10 for z < 0.43 and ρ(z) ∝ (1 + z)−8.44 ± 1.10 for z > 0.43. The local formation rate is |$\rho (0) = 0.03\, {\rm Gpc}^{-3} \, {\rm yr}^{-1}$| for some EE-I GRBs and |$\rho (0) = 0.32 \, {\rm Gpc}^{-3} \, {\rm yr}^{-1}$| for EE-II GRBs. Based on these results, we provide new evidence that the origins of EE-I GRBs are different from EE-II GRBs from the perspective of event rate. The EE-I GRB could be produced from the death of the massive star, but EE-II GRB may come from other processes that are unrelated to the star formation rate. Our findings indicate that the GRBs with EE could have multiple production channels. [ABSTRACT FROM AUTHOR]

The perovskite multiferroic bismuth ferrite (BiFeO3) particles were synthesized by hydrothermal method under external magnetic fields with respective intensities of 0 T, 4 T, 8 T, and 12 T. High magnetic field greatly affected the growth behavior and magnetic property of BiFeO3. The morphology of BiFeO3 changed from regular cube to irregular sphere, and finally became a chain-like structure. Meanwhile, the magnetization of the as-prepared BiFeO3 particles measured under a 1.8 T magnetic field was enhanced from 0.1003 emu/g (0 T) to 0.2067 emu/g (12 T). The possible mechanisms of crystal growth and magnetic property were also discussed. [ABSTRACT FROM AUTHOR]

The plasma generated by 1064 nm Nd:YAG laser irradiation of aluminum alloy in air at atmospheric pressure was studied spectroscopically. The electron density inferred by measuring the Stark-broadened line profile of Si(I) 288.16 nm decreases with increasing distance from the target surface. The electron temperature was determined using the Boltzmann plot method with nine strong neutral aluminum lines. Due to the thermal conduction towards the solid target and radiative cooling of the plasma as well as conversion of thermal energy into kinetic energy, the electron temperature decreases both at the plasma edge and close to the target surface. Electron density and electron temperature were also studied as functions of laser power density. At the same time, the validity of the assumption of local thermodynamic equilibrium and the effect of selfabsorption were discussed in light of the results obtained. [ABSTRACT FROM AUTHOR]