Proper Motions of H-alpha filaments in the Supernova Remnant RCW 86

We present a proper motion study of the eastern shock-region of the supernova remnant RCW 86 (MSH 14-63, G315.4-2.3), based on optical observations carried out with VLT/FORS2 in 2007 and 2010. For both the northeastern and southeastern regions, we measure an average proper motion of H-alpha filaments of 0.10 +/- 0.02 arcsec/yr, corresponding to 1200 +/- 200 km/s at 2.5kpc. There is substantial variation in the derived proper motions, indicating shock velocities ranging from just below 700 km/s to above 2200 km/s. The optical proper motion is lower than the previously measured X-ray proper motion of northeastern region. The new measurements are consistent with the previously measured proton temperature of 2.3 +/- 0.3 keV, assuming no cosmic-ray acceleration. However, within the uncertainties, moderately efficient (< 27 per cent) shock acceleration is still possible. The combination of optical proper motion and proton temperature rule out the possibility that RCW 86 has a distance less than 1.5kpc. The similarity of the proper motions in the northeast and southeast is peculiar, given the different densities and X-ray emission properties of the regions. The northeastern region has lower densities and the X-ray emission is synchrotron dominated, suggesting that the shock velocities should be higher than in the southeastern, thermal X-ray dominated, region. A possible solution is that the H-alpha emitting filaments are biased toward denser regions, with lower shock velocities. Alternatively, in the northeast the shock velocity may have decreased rapidly during the past 200yr, and the X-ray synchrotron emission is an afterglow from a period when the shock velocity was higher.Comment: Accepted for publication in MNRA

Measuring the cosmic ray acceleration efficiency of a supernova remnant

Cosmic rays are the most energetic particles arriving at earth. Although most of them are thought to be accelerated by supernova remnants, the details of the acceleration process and its efficiency are not well determined. Here we show that the pressure induced by cosmic rays exceeds the thermal pressure behind the northeast shock of the supernova remnant RCW 86, where the X-ray emission is dominated by synchrotron radiation from ultra-relativistic electrons. We determined the cosmic-ray content from the thermal Doppler broadening measured with optical spectroscopy, combined with a proper-motion study in X- rays. The measured post-shock proton temperature in combination with the shock velocity does not agree with standard shock heating, implying that >50% of the post-shock pressure is produced by cosmic rays.Comment: Published in Science express, 10 pages, 5 figures and 2 table

Chandra observations of SN 1987A: the soft X-ray light curve revisited

We report on the present stage of SN 1987A as observed by the Chandra X-ray Observatory. We reanalyze published Chandra observations and add three more epochs of Chandra data to get a consistent picture of the evolution of the X-ray fluxes in several energy bands. We discuss the implications of several calibration issues for Chandra data. Using the most recent Chandra calibration files, we find that the 0.5-2.0 keV band fluxes of SN 1987A have increased by ~6 x 10 ^-13 erg s^-1 cm^-2 per year since 2009. This is in contrast with our previous result that the 0.5-2.0 keV light curve showed a sudden flattening in 2009. Based on our new analysis, we conclude that the forward shock is still in full interaction with the equatorial ring.Comment: Accepted for publication by ApJ, 7 pages, 5 figure

Extrusion of poly(vinylidene fluoride) recycled filaments : effect of the processing cycles on the degree of crystallinity and electroactive phase content

This study analyses the possibility of reprocessing used poly(vinylidene fluoride), PVDF, maintaining the main properties critical for its use in piezoelectric sensor/actuator applications. The influence of multiple reprocessing cycles of PVDF on crystallinity and ß-phase content fundamental for its electroactive behaviour, was studied. Nine reprocessing cycles were completed and it was found that the material preserved the characteristics required for its use as piezoelectric polymer without significant degradation.The authors thank the Portuguese Foundation for Science and Technology (FCT) (gs1) for financial support under Project Piezotex - PTDC (PTDC/CTM/108801/2008) and in the framework of the Strategic Project PEst-C/FIS/ UI607/20112011, PEst-C/CTM/LA0025/2011 and PEst-C/CTM/UI0264/2011. MPS thanks the FCT for financial support under grant SFRH/BD/70303/2010

Production of polymer filament-shaped piezoelectric sensors for e-textiles applications

This work aims at the development of piezoelectric materials for flexible sensors produced with various geometries, at low cost and high production rates, adequate for the industrial scale. In particular the filament form, appropriate for integration into textiles, is described, but other geometries, such as tape, are also being studied. The filaments are produced by co-extrusion of multiple layers with piezoelectric and electrically conductive polymer composites.Fundação para a Ciência e a Tecnologia (FCT) - PTDC/CTM/108801/200

Piezoelectric filaments produced by coextrusion

Considering the significant interest of both the academic and industrial communities in the fields of i/e-textiles (interactive/electronic textiles), the number of developed applications is far below the expected. This fact is mainly related to the difficulties on the development of production methodologies adequate to industrial scale processes. In this areas the integration of piezoelectric materials, that possess sensing/actuating capabilities, such as poly(vinylidene fluoride), PVDF, and can be processed using conventional processing techniques, is very promising and has encouraged a large number of research works. However, until now, most of the developed production methodologies are difficult to adapt to the industrial scale. This work reports recent developments achieved, in the framework of a research project, on the production of piezoelectric filament by coextrusion of PVDF and electrical conductive layers. The developed production methodology involves a conventional coextrusion line, for which a coextrusion die was designed to produce a multilayer filament. This filament comprises an inner layer of an electrically conductive Polypropylene grade and a middle layer of PVDF and is coated with an electrical conductive ink. The piezoelectric response of the produced filaments will be also presentedFundação para a Ciência e a Tecnologia (FCT)- FCT PTDC/CTM/108801/200

Extrusion of piezoelectric filaments

The application of electroactive materials in textile products has a huge potential. However, the difficulties related to the integration in textile products of materials that possess those characteristics have limited the development of practical applications that fully exploit their capabilities. This works describes the development of a technology, which pursues the production of electroactive materials easy to integrate in textile products. For this purpose, multilayer piezoelectric filaments were produced by filament coextrusion. Poly(vinylidene fluoride) (PVDF) was used as the piezoelectric material and an electrical conductive thermoplastic grade, comprising a PP matrix, was used as the electrical conductive inner layer to produce a two-layer filament with coaxial layers. The samples were produced in a monofilament coextrusion line, and were stretched to ratios up to 6 at temperatures of 80ºC to 120ºC, to obtain the PVDF in -phase, the most electroactive phase of that material. The filaments were subsequently covered with a conductive ink and the PVDF layer was poled using high voltage applied between the inner conductive layer and the conductive ink. The piezoelectric properties of the produced filaments were evaluated in a test setup, designed to stimulate the filament mechanically by bending it periodically. A charge amplifier was used to condition the output signal. The results obtained confirm the piezoelectric property of the produced coextruded filaments, opening a new field of research and development directed to mechanical sensors/actuators in filament form.Fundação para a Ciência e a Tecnologia (FCT) - PTDC/CTM/108801/200

Effect of the processing conditions on the mechanical and electrical properties of extruded conductive PP tape and filament

Polypropylene (PP) shows a number of desirable properties that make it a versatile material among thermoplastic polymers. Due to its low cost and density, it is an excellent resin for conductive polymer composites (CPCs).[1] CPCs mainly consist on a polymer matrix with incorporated carbonaceous fillers. These multifunctional materials are routinely employed in various commercial applications due to their good electrical conductivity, corrosion resistance, light weight and enhanced mechanical properties. [2] The filler content is the crucial aspect in conductive polymer composites fabrication: due to mechanical behaviour it must be as low as possible but enough to allow fulfilling the electrical requirements.[2] In this work commercial conductive master batch PP was extruded in the form of tape and filament using different processing conditions, namely different draw ratios and temperatures. In order to tailor the mechanical performance of the material, different several amounts of PP homopolymer were added to the commercial conductive resin. The results show that the amount of homopolymer directly influences mechanical and electrical performance of the material. Increasing homopolymer content yields a more stretchable, and mechanically resistant, material but, on the other hand, reduces its electrical conductivity. This study focuses on the optimization of the processing conditions and composition in order to tailor the mechanical and electrical properties of the material for specific applicationsFundação para a Ciência e a Tecnologia (FCT) - PTDC/CTM/108801/2008, POCI 2010, Pluriannual program

Characterizing the non-thermal emission of Cas A

We report on our analysis of the 1 Ms Chandra observation of the supernova remnant Cas A in order to localize, characterize and quantify its non-thermal X-ray emission. More specifically, we investigated whether the X-ray synchrotron emission from the inside of the remnant is from the outward shock, but projected toward the inner ring, or from the inner shell. We tackle this problem by employing a Lucy-Richardson deconvolution technique and measuring spectral indices in the 4.2-6 keV band. We show that most of the continuum emission is coming from an inner ring that coincides with the location of the reverse shock. This inner ring includes filaments, whose X-ray emission has been found to be dominated by X-ray synchrotron emission. The X-ray emission from these filaments, both at the forward shock and from the inner ring, have relatively hard spectra with spectral index > -3.1. The regions emitting hard X-ray continuum contribute about 54% of the total X-ray emission in the 4.2-6 keV. This is lower than suggested by extrapolating the hard X-ray spectrum as measured by BeppoSAX-PDS and INTEGRAL. This can be reconciled by assuming a gradual steepening of the spectrum toward higher energies. We argue that the X-ray synchrotron emission is mainly coming from the Western part of the reverse shock. The reverse shock in the West is almost at rest in our observation frame, corresponding to a relatively high reverse shock velocity of ~6000 km/s in the frame of the freely expanding ejecta.Comment: Accepted for publication in ApJ, high resolution figures will appear in the official pape