Searching Signals in Chinese Ancient Records for the 14^{14}C Increases in AD 774-775 and in AD 992-993

According to the analysis of the $^{14}$C content of two Japanese trees over a period of approximately 3000 years at high time resolution, Miyake (2012) found a rapid increase at AD 774-775 and later on at AD 992-993 (Miyake 2013). This corresponds to a high-energy event happened within one year that input $\gamma$-ray energy about 7$\times{}$10$^{24}$erg to the Earth, leaving the origin a mystery. Such strong event should have an unusual optical counterpart, and have been recorded in historical literature. We searched Chinese historical materials around AD 744-775 and AD 992-993, but no remarkable event was found except a violent thunderstorm in AD 775. However, the possibility of a thunderstorm containing so much energy is still unlikely. We conclude the event caused the $^{14}$C increase is still unclear. This event most probably has no optical counterpart, and short gamma-ray burst, giant flare of a soft gamma-ray repeater and terrestrial $\gamma$-ray flash may all be the candidates.Comment: 8 pages, 3 figure

Constraining the Mass of the Photon with Gamma-Ray Bursts

One of the cornerstones of modern physics is Einstein's special relativity, with its constant speed of light and zero photon mass assumptions. Constraint on the rest mass m_{\gamma} of photons is a fundamental way to test Einstein's theory, as well as other essential electromagnetic and particle theories. Since non-zero photon mass can give rise to frequency-(or energy-) dependent dispersions, measuring the time delay of photons with different frequencies emitted from explosive astrophysical events is an important and model-independent method to put such a constraint. The cosmological gamma-ray bursts (GRBs), with short time scales, high redshifts as well as broadband prompt and afterglow emissions, provide an ideal testbed for m_{\gamma} constraints. In this paper we calculate the upper limits of the photon mass with GRB early time radio afterglow observations as well as multi-band radio peaks, thus improve the results of Schaefer (1999) by nearly half an order of magnitude.Comment: 25 pages, 2 tables, Accepted by Journal of High Energy Astrophysic

A Rational Self-Sacrificing Template Route to LiMn

Single-crystalline LiMn2O4 nanotubes and nanowires have been synthesized via a low-temperature molten salt synthesis method, using the prepared β-MnO2 nanotubes and α-MnO2 nanowires as the precursors and self-sacrificing template. The materials were investigated by a variety of techniques, including X-ray powder diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), and high-resolution transmission electron microscopy (HRTEM). The results indicate that the prepared LiMn2O4 nanotube and nanowire samples are both spinel phase, have lengths up to several micrometers and diameters of hundreds and tens of nanometers, respectively