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See detailDevelopment of an ELT XAO testbed using a self referenced Mach-Zehnder wavefront sensor
Delacroix, Christian ULiege; Loupias, Magali; Langlois, Maud et al

in Proceedings of the conference held 25-30 October, 2015 at UCLA (2015)

Extreme adaptive optics (XAO) has severe difficulties meeting the high speed (>1kHz), accuracy and photon efficiency requirements for future extremely large telescopes. An innovative high order adaptive ... [more ▼]

Extreme adaptive optics (XAO) has severe difficulties meeting the high speed (>1kHz), accuracy and photon efficiency requirements for future extremely large telescopes. An innovative high order adaptive optics system using a self-referenced Mach-Zehnder wavefront sensor (MZWFS) allows counteracting these limitations. In addition to its very high accuracy, this WFS is the most robust alternative to segments gaps and telescope spiders which can result in strong wavefront artifacts. In particular in XAO systems when the size of these gaps in the wavefront measurement is comparable to the sub aperture size, loss in performance can be very high. The MZWFS estimates the wavefront phase by measuring intensity differences between two outputs, with a λ/4 path length difference between its two legs, but is limited in dynamic range. During the past few years, such an XAO system has been studied by our team in the framework of 8-meter class telescopes. In this paper, we report on our latest results with the XAO testbed recently installed in CRAL laboratory, and dedicated to high contrast imaging with 30m-class telescopes (such as the E-ELT or the TMT). A woofer-tweeter architecture is used in order to deliver the required high Strehl ratio (>95%). It consists of a 12x12 deformable mirror (DM) and a 512x512 Spatial Light Modulator (SLM) characterized both using monochromatic and polychromatic light. We present our latest experimental results, including components characterization, close loop performances and sensitivity to calibration errors. This work is carried out in synergy with the validation of fast iterative wavefront reconstruction algorithms and the optimal treatment of phase ambiguities in order to mitigate the dynamical range limitation of such a wavefront sensor. [less ▲]

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See detailA Practical tool to assess the cross cutting nature of child injury prevention as a basis for policy making at the local level
Scholtes, Béatrice ULiege; Schröder-Bäck, Peter; Mackay, Morag et al

in South Eastern European Journal of Public Health (2014), 1(1),

Aim: Risk factors for child injury are multi-faceted. Social, environmental and economic factors place responsibility for prevention upon many stakeholders across traditional sectors such as health ... [more ▼]

Aim: Risk factors for child injury are multi-faceted. Social, environmental and economic factors place responsibility for prevention upon many stakeholders across traditional sectors such as health, justice, environment and education. Multi-sectoral collaboration for injury prevention is thus essential. In addition, co-benefits due to injury prevention initiatives exist. However, multi-sectoral collaboration is often difficult to establish and maintain. We present an applied approach for practitioners and policy makers at the local level to use to explore and address the multi-sectoral nature of child injury. Methods: We combined elements of the Haddon Matrix and the Lens and Telescope model, to develop a new approach for practitioners and policy makers at the local level. Results: The approach offers the opportunity for diverse sectors at the local level to work together to identify their role in child injury prevention. Based on ecological injury prevention and life-course epidemiology it encourages multi-disciplinary team building from the outset. The process has three phases: first, visualising the multi-sectoral responsibilities for child injury prevention in the local area; second, demonstrating the need for multi-sectoral collaboration and helping plan prevention activities together; and third, visualising potential co-benefits to other sectors and age groups that may arise from child injury prevention initiatives. Conclusion: The approach and process encourages inter-sectoral collaboration for child injury prevention at the local level. It is a useful addition for child injury prevention at the local level, however testing the practicality of the approach in a real-world setting, and refinement of the process would improve it further. [less ▲]

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See detailProjective vs. interpretational properties of nuclear accents and the phonology of contrastive focus in Greek
Georgakopoulos, Athanasios ULiege; Skopeteas, Stavros

in The Linguistic Review (2010), 27

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See detailMicrolensing variability in the gravitationally lensed quasar QSO 2237+0305 = the Einstein Cross . I. Spectrophotometric monitoring with the VLT
Eigenbrod, Alexander; Courbin, Frederic; Sluse, Dominique ULiege et al

in Astronomy and Astrophysics (2008), 480

We present the results of the first long-term (2.2 years) spectroscopic monitoring of a gravitationally lensed quasar, namely the Einstein Cross QSO 2237+0305. The goal of this paper is to present the ... [more ▼]

We present the results of the first long-term (2.2 years) spectroscopic monitoring of a gravitationally lensed quasar, namely the Einstein Cross QSO 2237+0305. The goal of this paper is to present the observational facts to be compared in follow-up papers with theoretical models to constrain the inner structure of the source quasar. We spatially deconvolve deep VLT/FORS1 spectra to accurately separate the spectrum of the lensing galaxy from the spectra of the quasar images. Accurate cross-calibration of the 58 observations at 31-epoch from October 2004 to December 2006 is carried out with non-variable foreground stars observed simultaneously with the quasar. The quasar spectra are further decomposed into a continuum component and several broad emission lines to infer the variations of these spectral components. We find prominent microlensing events in the quasar images A and B, while images C and D are almost quiescent on a timescale of a few months. The strongest variations are observed in the continuum of image A. Their amplitude is larger in the blue (0.7 mag) than in the red (0.5 mag), consistent with microlensing of an accretion disk. Variations in the intensity and profile of the broad emission lines are also reported, most prominently in the wings of the C III and center of the C IV emission lines. During a strong microlensing episode observed in June 2006 in quasar image A, the broad component of the C III is more highly magnified than the narrow component. In addition, the emission lines with higher ionization potentials are more magnified than the lines with lower ionization potentials, consistent with the results obtained with reverberation mapping. Finally, we find that the V-band differential extinction by the lens, between the quasar images, is in the range 0.1-0.3 mag. [less ▲]

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See detailPaires de quasars et mirages gravitationnels : Etudes observationnelles et implications astrophysiques
Sluse, Dominique ULiege

Doctoral thesis (2005)

The present work deals with the gravitational lensing phenomenon through the study of three pairs of quasars with different redshifts separated by a few arcseconds on the sky as well as through the study ... [more ▼]

The present work deals with the gravitational lensing phenomenon through the study of three pairs of quasars with different redshifts separated by a few arcseconds on the sky as well as through the study of a new gravitationnally lensed system that we had the chance to serendipitously discover during our thesis. In the first part, we investigate the possibility of measuring the mass of the foreground quasar using the latter as a potential cosmic lens that deviates the light from the background quasar. For this purpose, we have observed with the Hubble Space Telescope (HST) the known close quasar pairs with discrepant redshifts in order to unveil secondary images of the background quasar in the vicinity of the foreground one. Among the three known quasar pairs, Q1009-0252 possesses one of its two components lensed by a foreground galaxy. Because of the lack of a spectrum of the lensing galaxy, we have combined various data sets obtained for this system in order to determine its type and its redshift as well as the causes of the observed chromatic differences in the flux ratios between the two lensed images. Finally, motivated by the results of Burbidge et al. (1997) ,we have re-examined the expected number of quasar pairs (with different redshifts) that should have been discovered. The second part is dedicated to the study of the complex gravitationally lensed system RXS J113155.4-123155. First, we expose the results related to the discovery of this system and discuss its properties (i.e. number of images, their relative positions, their brightnesses, redshifts of the source and of the lensing galaxy). Next, we present the results obtained from the multi-colour and multi-epoch follow-up imaging of this sytem. These results include the level of differential extinction affecting the lensed images, the confirmation of an important level of intrinsic variability of the source, the evidence of a microlensing event affecting one of the lensed image as well as a modeling of the lensing galaxy. This analysis enabled us to understand the possible phenomena responsible for the observed flux ratios. [less ▲]

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