3 to 12 millimetre studies of dense gas towards the western rim of supernova remnant RX J1713.7-3946

The young X-ray and gamma-ray-bright supernova remnant RXJ1713.7-3946 (SNR G347.3-0.5) is believed to be associated with molecular cores that lie within regions of the most intense TeV emission. Using the Mopra telescope, four of the densest cores were observed using high-critical density tracers such as CS(J=1-0,J=2-1) and its isotopologue counterparts, NH3(1,1) and (2,2) inversion transitions and N2H+(J=1-0) emission, confirming the presence of dense gas >10^4cm^-3 in the region. The mass estimates for Core C range from 40M_{\odot} (from CS(J=1-0)) to 80M_{\odot} (from NH3 and N2H+), an order of magnitude smaller than published mass estimates from CO(J=1-0) observations. We also modelled the energy-dependent diffusion of cosmic-ray protons accelerated by RXJ1713.7-3946 into Core C, approximating the core with average density and magnetic field values. We find that for considerably suppressed diffusion coefficients (factors \chi=10^{-3} down to 10^{-5} the galactic average), low energy cosmic-rays can be prevented from entering the inner core region. Such an effect could lead to characteristic spectral behaviour in the GeV to TeV gamma-ray and multi-keV X-ray fluxes across the core. These features may be measurable with future gamma-ray and multi-keV telescopes offering arcminute or better angular resolution, and can be a novel way to understand the level of cosmic-ray acceleration in RXJ1713.7-3946 and the transport properties of cosmic-rays in the dense molecular cores.Comment: 17 pages, 13 figures and 5 tables. Accepted for publication in MNRAS 2012 February 1

Flexible, Flame-Resistant, and Dendrite-Impermeable Gel-Polymer Electrolyte for Li�O<inf>2</inf>/Air Batteries Workable Under Hurdle Conditions

© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Gel-polymer electrolytes are considered as a promising candidate for replacing the liquid electrolytes to address the safety concerns in Li–O2/air batteries. In this work, by taking advantage of the hydrogen bond between thermoplastic polyurethane and aerogel SiO2in gel polymer, a highly crosslinked quasi-solid electrolyte (FST-GPE) with multifeatures of high ionic conductivity, high mechanical flexibility, favorable flame resistance, and excellent Li dendrite impermeability is developed. The resulting gel-polymer Li–O2/air batteries possess high reaction kinetics and stabilities due to the unique electrode–electrolyte interface and fast O2diffusion in cathode, which can achieve up to 250 discharge–charge cycles (over 1000 h) in oxygen gas. Under ambient air atmosphere, excellent performances are observed for coin-type cells over 20 days and for prototype cells working under extreme bending conditions. Moreover, the FST-GPE electrolyte also exhibits durability to protect against fire, dendritic Li, and H2O attack, demonstrating great potential for the design of practical Li–O2/air batteries

The Imaging X-Ray Polarimetry Explorer (IXPE): Pre-Launch

International audienceLaunched on 2021 December 9, the Imaging X-ray Polarimetry Explorer (IXPE) is a NASA Small Explorer Mission in collaboration with the Italian Space Agency (ASI). The mission will open a new window of investigation—imaging x-ray polarimetry. The observatory features three identical telescopes, each consisting of a mirror module assembly with a polarization-sensitive imaging x-ray detector at the focus. A coilable boom, deployed on orbit, provides the necessary 4-m focal length. The observatory utilizes a three-axis-stabilized spacecraft, which provides services such as power, attitude determination and control, commanding, and telemetry to the ground. During its 2-year baseline mission, IXPE will conduct precise polarimetry for samples of multiple categories of x-ray sources, with follow-on observations of selected targets