Neutrino emission from a GRB afterglow shock during an inner supernova shock breakout

The observations of a nearby low-luminosity gamma-ray burst (GRB) 060218 associated with supernova SN 2006aj may imply an interesting astronomical picture where a supernova shock breakout locates behind a relativistic GRB jet. Based on this picture, we study neutrino emission for early afterglows of GRB 060218-like GRBs, where neutrinos are expected to be produced from photopion interactions in a GRB blast wave that propagates into a dense wind. Relativistic protons for the interactions are accelerated by an external shock, while target photons are basically provided by the incoming thermal emission from the shock breakout and its inverse-Compton scattered component. Because of a high estimated event rate of low-luminosity GRBs, we would have more opportunities to detect afterglow neutrinos from a single nearby GRB event of this type by IceCube. Such a possible detection could provide evidence for the picture described above.Comment: 6 pages, 2 figures, accepted for publication in MNRA

Effects of lattice mismatch on interfacial structures of liquid and solidified Al in contact with hetero-phase substrates: MD simulations

Published under licence in IOP Conference Series: Material Science and Engineering by IOP Publishing Ltd. Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.In this study, the effects of the misfit on in-plane structures of liquid Al and interfacial structure of solidified Al in contact with the heterophase substrates have been investigated, using molecular dynamics (MD) simulations. The MD simulations were conducted for Al/fcc (111) substrates with varied misfits. The order parameter and atomic arrangement indicated that the in-plane ordering of the liquid at the interface decreases significantly with an increase of the misfit, i.e., solid-like for small misfit and liquid-like for large misfit. Further, our MD simulation results revealed that a perfect orientation relationship forms at the interface between the substrate and the solidified Al for a misfit of less than -3% and the boundary is coherent. With an increase in the misfit, Shockley partial and extended dislocations form at the interface, and the boundary becomes a semi-coherent or low-angle twist boundary.EPSR

Diffusion of a liquid nanoparticle on a disordered substrate

We perform molecular dynamic simulations of liquid nanoparticles deposited on a disordered substrate. The motion of the nanoparticle is characterised by a 'stick and roll' diffusive process. Long simulation times ($\simeq \mu s$), analysis of mean square displacements and stacking time distribution functions demonstrate that the nanoparticle undergoes a normal diffusion in spite of long sticking times. We propose a phenomenological model for the size and temperature dependence of the diffusion coefficient in which the activation energy scales as $N^{1/3}$.Comment: Accepted for publication in Phys. Rev.

The X-ray Spectral Properties and Variability of Luminous High-Redshift Active Galactic Nuclei

We perform a detailed investigation of moderate-to-high quality X-ray spectra of ten of the most luminous active galactic nuclei (AGNs) known at z>4 (up to z~6.28). This study includes five new XMM observations and five archived X-ray observations (four by XMM and one by Chandra). We find that the X-ray power-law photon indices of our sample, composed of eight radio-quiet sources and two that are moderately radio loud, are not significantly different from those of lower redshift AGNs. The upper limits obtained on intrinsic neutral hydrogen column densities, N_H<~10^{22}-10^{23} cm^{-2}, indicate that these AGNs are not significantly absorbed. A joint fit performed on our eight radio-quiet sources, with a total of ~7000 photons, constrains the mean photon index of z>4 radio-quiet AGNs to Gamma=1.97^{+0.06}_{-0.04}, with no detectable intrinsic dispersion from source to source. We also obtain a strong constraint on the mean intrinsic column density, N_H<~3x10^{21} cm^{-2}, showing that optically selected radio-quiet AGNs at z>4 are, on average, not more absorbed than their lower-redshift counterparts. All this suggests that the X-ray production mechanism and the central environment in radio-quiet AGNs have not significantly evolved over cosmic time. The mean equivalent width of a putative neutral narrow Fe Ka line is constrained to be <~190 eV, and similarly we place constraints on the mean Compton reflection component (R<~1.2). None of the AGNs varied on short (~1 hr) timescales, but on longer timescales (months-to-years) strong variability is observed in four of the sources. In particular, the X-ray flux of the z=5.41 radio-quiet AGN SDSS 0231-0728 dropped by a factor of ~4 over a rest-frame period of 73 d. This is the most extreme X-ray variation observed in a luminous z>4 radio-quiet AGN.Comment: 10 pages (emulateapj), 5 figures. Accepted by Ap

A change of IL-2 and IL-4 production in patients with Helicobactor pylori infection

Hellcobacter pylori is the most common cause of gastroduodenal inflammation. However, the exact immune pathogenesis is not fully understood. To look for evidence of the immunological mechanism in H. pylori associated disease, we measured cytokine interleukin-2 (IL-2) and IL-4 levels produced by peripheral blood lymphocytes (PBL) and gastric biopsies in 20 subjects with or without H. pylori infection. H. pylori can stimulate IL-2 and IL-4 production from PBL in H. pylori negative as well as H. pylori positive individuals. The spontaneous IL-2 production by PBL and gastric biopsies was greater (p < 0.0025, <0.001)in H. pylori negative individuals than that in H. pylori infected patients. Increased IL-4 levels from PBL in H. pylori infected patients were found in the presence of H. pylori (p < 0.0025). An increased spontaneous production of IL-4 from gastric biopsies was also observed in H. pylori infected patients (p < 0.025). In conclusion, an enhanced type 2 cytokine production was observed in H. pylori infected patients, which may be responsible for H. pylori chronic infection