Observational Search for PeV-EeV Tau Neutrino from GRB081203A

We report the first observational search for tau neutrinos from gamma ray bursts (GRBs) using one of the Ashra light collectors. The earth-skimming tau-neutrino technique of imaging Cherenkov tau showers was applied as a detection method. We set stringent upper limits on the tau-neutrino fluence in PeV-EeV region for 3780 s (between 2.83 and 1.78 hours before) and another 3780 s (between 21.2 and 22.2 hours after) surrounding GRB081203A triggered by the Swift satellite. This first search for PeV-EeV tau neutrino complements other experiments in energy range and methodology, and suggests the prologue of "multi-particle astronomy" with a precise determination of time and location.Comment: 13 pages, 4 figure

Molecular-Dynamics Simulation of Lattice Thermal Conductivity in Pb_<1-x>Sn_xTe and Pb_<1-x>Ge_xTe at High Temperature

The molecular-dynamics studies on lattice thermal conductivity (κ_L) of Pb_Sn_xTe and Pb_Ge_xTe are carried out by employing ion model potential for mutual ion-ion interactions at the average temperatures 300 and 500 K under non-equilibrium condition. Special emphasis of investigation is on the alloying effects on κ_L by changing the alloying content x of Sn and Ge in PbTe. It has been shown that a remarkable reduction of κ_L at finite x is demonstrated in Pb_Sn_xTe and Pb_Ge_xTe without a relying on a phonon scattering description. We have compared our results with ones evaluated by the Abeles' formula of lattice thermal conductivity due to phonon scattering from alloy fluctuations