Radio emission from Supernova Remnants

The explosion of a supernova releases almost instantaneously about 10^51 ergs of mechanic energy, changing irreversibly the physical and chemical properties of large regions in the galaxies. The stellar ejecta, the nebula resulting from the powerful shock waves, and sometimes a compact stellar remnant, constitute a supernova remnant (SNR). They can radiate their energy across the whole electromagnetic spectrum, but the great majority are radio sources. Almost 70 years after the first detection of radio emission coming from a SNR, great progress has been achieved in the comprehension of their physical characteristics and evolution. We review the present knowledge of different aspects of radio remnants, focusing on sources of the Milky Way and the Magellanic Clouds, where the SNRs can be spatially resolved. We present a brief overview of theoretical background, analyze morphology and polarization properties, and review and critical discuss different methods applied to determine the radio spectrum and distances. The consequences of the interaction between the SNR shocks and the surrounding medium are examined, including the question of whether SNRs can trigger the formation of new stars. Cases of multispectral comparison are presented. A section is devoted to reviewing recent results of radio SNRs in the Magellanic Clouds, with particular emphasis on the radio properties of SN 1987A, an ideal laboratory to investigate dynamical evolution of an SNR in near real time. The review concludes with a summary of issues on radio SNRs that deserve further study, and analyzing the prospects for future research with the latest generation radio telescopes.Comment: Revised version. 48 pages, 15 figure

Controlling surface chemistry and mechanical properties of metal ionogels through Lewis acidity and basicity

Ionogels are emerging as soft materials with remarkable physical properties that can be tuned to suit application requirements. The liquid component—ionic liquids—are effectively involatile, which provides new opportunities to explore gel surfaces with UHV based analytical techniques. Here, we exploit the highly solvating nature of ionic liquids to fabricate poly(ethylene glycol) based ionogels with high concentrations of zinc, and then investigate their surfaces to show that tunability extends beyond the bulk to the interface. A unique relationship between Lewis acidity and basicity and the surface concentration of metal was revealed. Chemical state analysis and molecular dynamics showed that Lewis acidic metals templated polymers to give new architectures reduced brittleness and increased flexibility, while Lewis basic metals improved polymer uniformity and strengthened gels. Therefore, bulk structure, surface composition, and metal speciation were all found to be intimately related and dependent upon the coordination strengths of ionic liquid anions. Importantly, the highly controllable surface and structural properties of metal ionogels allow fine-tuning across a broad design space, which presents new opportunities for gel based applications

Thermally robust solvent-free biofluids of M13 bacteriophage engineered for high compatibility with anhydrous ionic liquids

Here, we demonstrate a chemical modification strategy to create biomaterials of the M13 bacteriophage with extraordinary thermal stability, and high compatibility with non-aqueous ionic liquids. The results provide a blueprint for developing soft materials with well-defined architectures that may find broad applicability in the next generation of flexible devices

Non-aqueous homogenous biocatalytic conversion of polysaccharides in ionic liquids using chemically modified glucosidase

The increasing requirement to produce platform chemicals and fuels from renewable sources means advances in biocatalysis are rapidly becoming a necessity. Biomass is widely used in nature as a source of energy and as chemical building blocks. However, recalcitrance towards traditional chemical processes and solvents provides a significant barrier to widespread utility. Here, by optimizing enzyme solubility in ionic liquids, we have discovered solvent-induced substrate promiscuity of glucosidase, demonstrating an unprecedented example of homogeneous enzyme bioprocessing of cellulose. Specifically, chemical modification of glucosidase for solubilization in ionic liquids can increase thermal stability to up to 137 °C, allowing for enzymatic activity 30 times greater than is possible in aqueous media. These results establish that through a synergistic combination of chemical biology (enzyme modification) and reaction engineering (solvent choice), the biocatalytic capability of enzymes can be intensified: a key step towards the full-scale deployment of industrial biocatalysis

Expanding the design space of gel materials through ionic liquid mediated mechanical and structural tuneability

Ionogels are an emerging class of soft material with exceptional properties stemming from high ionic liquid content. In contrast to other gel systems, the ionic liquid component provides an extra level of design. However, this highly modular nature has yet to be fully explored and the role ionic liquids play in the structural properties of gel-based materials is poorly understood. Here, methodical small angle neutron scattering and X-ray photoelectron spectroscopy studies reveal the relationship between bulk structure and surface composition of a soft material for the first time. Furthermore, we show how ionic liquid design dictates polymer structure, which in turn can be harnessed to fine tune the mechanical properties of ionogels. With a level of control over gel structure beyond what is possible using molecular solvents, our systematic study thus provides insight into how ionic liquids can expand the design space for gel development for a broad range of applications