Implications of H.E.S.S. observations of pulsar wind nebulae

In this review paper on pulsar wind nebulae (PWN) we discuss the properties of such nebulae within the context of containment against cross-field diffusion (versus normal advection), the effect of reverse shocks on the evolution of offset ``Vela-like'' PWN, constraints on maximum particle energetics, magnetic field strength estimates based on spectral and spatial properties, and the implication of such field estimates on the composition of the wind. A significant part of the discussion is based on the High Energy Stereoscopic System ({\it H.E.S.S.} or {\it HESS}) detection of the two evolved pulsar wind nebulae Vela X (cocoon) and HESS J1825-137. In the case of Vela X (cocoon) we also review evidence of a hadronic versus a leptonic interpretation, showing that a leptonic interpretation is favored for the {\it HESS} signal. The constraints discussed in this review paper sets a general framework for the interpretation of a number of offset, filled-center nebulae seen by {\it HESS}. These sources are found along the galactic plane with galactic latitudes $|b|\sim 0$, where significant amounts of molecular gas is found. In these regions, we find that the interstellar medium is inhomogeneous, which has an effect on the morphology of supernova shock expansion. One consequence of this effect is the formation of offset pulsar wind nebulae as observed.Comment: to appear in Springer Lecture Notes on Neutron Stars and Pulsars: 40 years after their discovery, eds. W. Becke

The 2014 ALMA Long Baseline Campaign: First Results from High Angular Resolution Observations toward the HL Tau Region

Interstellar matter and star formatio

The 2014 ALMA Long Baseline Campaign: An Overview

Instrumentatio

Microstructural Evolution by Continuous Recrystallization in a Superplastic Al-Mg Alloy

The boundary misorientations in an Al-1OMg-O.1Zr (wt%) alloy, thermomechanically processed by rolling at 573 K (300°C), were determined both in annealed and in superplastically deformed conditions. A high initial dislocation density in as-rolled material, which obscured any underlying structure, rapidly transformed into a well-defined structure containing boundaries. After annealing for 600 s at 573K, boundaries with misorientations of 1–5° were observed. With further annealing (3000 s), misorientations did not change appreciably and were measured to be 2–7°. Such time represents that necessary to equilibrate at 573K prior to tension testing at that temperature. The material exhibits superplasticity from the onset of deformation and after 100% strain, misorientations were observed to increase to 20–30°. It was concluded that boundaries of such initial misorientations can support superplastic deformation mechanisms including grain boundary sliding.U.S. Naval Air Systems CommandUniversity of Illinoi

An EBSP investigation of alternate microstructures for superplasticity in aluminum-magnesium alloys

The article of record as published may be found at http://dx.doi.org/101016/S1359-6462(96)00403-4This study proposes to provide insight into alternative grain boundary structures in two aluminum-magnesium alloys processed to achieve superplastic behavior. A commercially processes superplastic 5083 aluminum alloy, SKY5083, and a laboratory processed, non-commercial superplastic Al-10Mg-0.1Zr alloy have been selected for examination. Although alloy content, processing routes, and deformation conditions vary for each material, a comparison of results may provide evidence that alternate grain structures and boundary misorientation distributions may support superplasticity in the GBS regime, depending on the TMP processing and alloy system chosen

GRAIN REFINEMENT AND SUPERPLASTICITY IN A LITHIUM-CONTAINING Al-Mg ALLOY BY THERMOMECHANICAL PROCESSING

The refined microstructures and superplastic properties resulting from controlled thermomechanical processing of an Al-8Mg-0.5Li-0.23Zr alloy were evaluated. Rolling between the solvus temperatures for Mg and Li in the alloy allowed for grain refinement by precipitation of β (Al8Mg5) during deformation and subsequent precipitation of δ' (Al3Li) on cooling. Increasing the rolling strain enhance the superplastic ductility of the alloy at 573K in the strain-rate regime of 10-3-10-2 S-1. Elongations in excess of 500 pct. , without cavitation, and a corresponding strain-rate sensitivity coefficient of approximately 0.5, were obtained. TEM investigations of the microstructural characteristics responsible for the mechanical behavior revealed that a more uniformly refined grain structure (3-5µm) evolved by continuous recrystallization (CRX) in material experiencing the larger rolling strain

Vanda Country Report

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