Search

Despite the popularity of the Evidence-Based Policy Making paradigm, scholarly evidence often fails to have an impact in emotional or value-laden policy debates. Consequently, changes to Canada’s gun control laws in recent years have often failed to incorporate scholarly research. This is problematic given that the forces of path dependence impose costs on policy makers who seek to reverse established policies, even if they are dysfunctional. This article lays the theoretical foundations for a Firearms Policy Evaluation Framework, which can be used by scholars, policy makers, advocates, and the public to conduct preliminary evaluations of proposed firearms policies before they become law. The utility of the framework is then demonstrated with an evaluation of the 2020 assault-style weapons ban in Canada, which includes a systematic scoping review of the literature on the impact of assault-weapons bans.

International audience; The next generation of Extremely Large Telescope (24 to 39m diameter) will suffer from the so-called "pupil fragmentation" problem. Due to their pupil shape complexity (segmentation, large spiders ...), some differential pistons may appear between some isolated part of the full pupil during the observations. Although classical AO system will be able to correct for turbulence effects, they will be blind to this specific telescope induced perturbations. Hence, such differential piston, a.k.a petal modes, will prevent to reach the diffraction limit of the telescope and ultimately will represent the main limitation of AO-assisted observation with an ELT. In this work we analyse the spatial structure of these petal modes and how it affects the ability of a Pyramid Wavefront sensor to sense them. Then we propose a variation around the classical Pyramid concept for increasing the WFS sensitivity to this particular modes. Nevertheless, We show that one single WFS can not accurately and simultaneously measure turbulence and petal modes. We propose a double path wavefront sensor scheme to solve this problem. We show that such a scheme,associated to a spatial filtering of residual turbulence in the second WFS path dedicated to petal mode sensing, allows to fully measure and correct for both turbulence and fragmentation effects and will eventually restore the full capability and spatial resolution of the future ELT.; La prochaine génération de Télescope Extrêmement Large (de 24 a 39m de diamètre) souffrira du problème de fragmentation de la pupille. Du a la complexité de la pupille de ces télescopes (segmentation, grande araignée, ...) des différences de piston peuvent apparaître entre les fragments de la pupille. Les systèmes d'Optique adaptative (OA) censées corrigés l'effet de turbulence seront aveugles a ces perturbations induites par la structure du télescope. Ces effets de piston différentiels souvent nommés mode pétale nous empêcheront d'atteindre la limite de diffraction du télescope et peut représenter la limite des observations assistés par Optique Adaptatives. Dans ce travail nous étudions la structure spatial de ces modes pétales et comment cela affecte la capacité du senseur pyramide a le mesurer. Ensuite nous proposons une modification du senseur pyramide pour améliorer la sensibilité au mode pétale. Néanmoins, nous avons montré qu'un seul ne peut pas être efficace pour mesurer en même temps la turbulence et les modes pétales. Nous proposons un senseur a deux voies pour résoudre ce problème. Nous montrons aussi qu'un tel schéma, associé a un filtrage spatial des résidus de turbulence permet de mesurer plus complétement et corriger la turbulence et les effets de fragmentation et finalement permet de restaurer la capacité et résolution compléte des futurs ELT.

For space-based Earth Observations and solar system observations, obtaining both high revisit rates (using a constellation of small platforms) and high angular resolution (using large optics and therefore a large platform) is an asset for many applications. Unfortunately, they prevent the occurrence of each other. A deployable satellite concept has been suggested that could grant both assets by producing jointly high revisit rates and high angular resolution of roughly 1 meter on the ground. This concept relies however on the capacity to maintain the phasing of the segments at a sufficient precision (a few tens of nanometers at visible wavelengths), while undergoing strong and dynamic thermal gradients. In the constrained volume environment of a CubeSat, the system must reuse the scientific images to measure the phasing errors. We address in this paper the key issue of focal-plane wave-front sensing for a segmented pupil using a single image with deep learning. We show a first demonstration of measurement on a point source. The neural network is able to identify properly the phase piston-tip-tilt coefficients below the limit of 15nm per petal., Pour les observations spatiales de la Terre et du système solaire, l'obtention à la fois de taux de revisite élevés (en utilisant une constellation de petites plates-formes) et une haute résolution angulaire (en utilisant de grandes optiques et donc une grande plate-forme) est un atout pour de nombreuses applications. Malheureusement, elles s'excluent l'une et de l'autre. Un concept de satellite déployable a été suggéré, qui pourrait garantir ces deux atouts en produisant conjointement des taux de revisite élevés et une haute résolution angulaire d'environ 1 mètre au sol.Ce concept repose cependant sur la capacité à maintenir le phasage des segments à une précision suffisante (quelques dizaines de nanomètres aux longueurs d'onde visibles), tout en subissant des gradients thermiques forts et dynamiques. Dans l'environnement volumique contraint d'un CubeSat, le système doit réutiliser les images scientifiques pour mesurer leserreurs de phasage.Nous abordons dans cet article le problème clé de la détection du front d'onde du plan focal pour une pupille segmentée en utilisant une seule image avec l'apprentissage profond. Nous montrons une première démonstration de mesure sur une source ponctuelle.Le réseau neuronal est capable d'identifier correctement les coefficients de phase piston-pointe-inclinaison en dessous de la limite de 15nm par pétale.

This account of practice details an ongoing approach to entrepreneurship education currently being implemented at a large urban university in Toronto, Canada. The Music Den is an entrepreneurship incubator focusing on the music industry that collaborates with start-up businesses, music projects, industry, local communities and postsecondary students. The incubator deploys a pedagogical model that promotes self-direction and mentorship by way of adaptable curricular programming. The program design utilizes social constructivist principles to deliver a novel entrepreneurship education curriculum.

International audience; This paper describes the outcomes of a study funded by the European Space Agency aimed at identifying the technical challenges and trade-offs at the system level, performing preliminary designs of an active correction loop for large deployable telescopes, and defining technological roadmaps for the development of the active correction loop for the selected designs. This study has targeted two very different application cases, one for High Resolution Earth Observation from Geostationary orbit (called GeoHR, with a 4m diameter entrance pupil) and one for Science missions requiring very large telescopes (with a up to 18 m diameter entrance pupil) with high-contrast imaging capabilities for exo-Earth observations and characterization. For both application cases, this paper first summarizes the mission objectives and constraints that have influence on the telescope designs. It then presents the high-level trade-offs that have been led and the optical and mechanical design that have been developed, including the deployable aspects. Finally, the performance assessment is presented, and is the basis for the justification of an active optics correction chain, with a preliminary set of requirements for typical components of the system. The presentation is concluded with proposed technological roadmaps that aim to allow the development of the building blocks on which the next generation instruments will be able to rely on.

Combining high-contrast imaging with medium-resolution spectroscopy has been shown to significantly boost the direct detection of exoplanets. HARMONI, one of the first-light instruments to be mounted on ESO's ELT, will be equipped with a single-conjugated adaptive optics system to reach the diffraction limit of the ELT in H and K bands, a high-contrast module dedicated to exoplanet imaging, and a medium-resolution (up to R = 17 000) optical and near-infrared integral field spectrograph. Combined together, these systems will provide unprecedented contrast limits at separations between 50 and 400 mas. In this paper, we estimate the capabilities of the HARMONI high-contrast module for the direct detection of young giant exoplanets. We use an end-to-end model of the instrument to simulate observations based on realistic observing scenarios and conditions. We analyze these data with the so-called "molecule mapping" technique combined to a matched-filter approach, in order to disentangle the companions from the host star and tellurics, and increase the S/N of the planetary signal. We detect planets above 5-sigma at contrasts up to 16 mag and separations down to 75 mas in several spectral configurations of the instrument. We show that molecule mapping allows the detection of companions up to 2.5 mag fainter compared to state-of-the-art high-contrast imaging techniques based on angular differential imaging. We also demonstrate that the performance is not strongly affected by the spectral type of the host star, and that we reach close sensitivities for the best three quartiles of observing conditions at Armazones, which means that HARMONI could be used in near-critical observations during 60 to 70% of telescope time at the ELT. Finally, we simulate planets from population synthesis models to further explore the parameter space that HARMONI and its high-contrast module will soon open., Accepted for publication in A&A (14 pages, 9 figures)

International audience; The volume available on-board small satellites limit the optical aperture to a few centimetres, which limits the Ground-Sampling Distance (GSD) in the visible to approximately 3 m at 500 km. We present the latest development of a laboratory demonstrator for a deployable telescope that will triple the achievable ground resolution and quadruple the photometric capability from a CubeSat imager. In this paper, we present the overall opto-mechanical design of a Cassegrain telescope with a segmented primary mirror with a 30 cm baseline. The segments are folded for launch and unfold in space. To enable diffraction-limited imaging, piston, tip, and tilt (PTT) on each of the mirror segments should be below 12 nm RMS. The key challenge is to ensure phasing, and this precision level will require an active phasing stage. We present laboratory results of deployment and active phasing of the primary mirror segments. The initial deployment is performed using shaped memory alloy that deploy mirror segments. We demonstrate a repeatability below ±4.5 µm, enabling the four PSFs (one for each mirror segment) to be imaged on the detector simultaneously. An alignment step using compact and calibrated capacitive sensors allows for a control of the mirror positions in PTT below the wavelength. Finally, we investigate the sensitivity of misalignments of a deployable secondary mirror and show that it is well within reach of the technology developed in this study.

International audience; The volume available on-board small satellites limit the optical aperture to a few centimetres, which limits the Ground- Sampling Distance (GSD) in the visible to approximately 3 m at 500 km. We present a performance analysis of the concept of a deployable CubeSat telescope. This payload will allow a tripling of the ground resolution achievable from a CubeSat imager, hence allowing very high resolution imaging from Low Earth Orbit (LEO). The project combines precision opto-mechanical deployment and cophasing of the mirrors segments using active optics. The payload has the potential of becoming a new off-the-shelf standardised system to be proposed for all high angular resolution imaging missions using CubeSats or similar nanosats. Ultimately, this technology will develop new instrumentation and technology for small satellite platforms with a primary mirror size equal or larger than 30 cm. In this paper, we present the breakdown of the different error sources that may affect the final optical quality and propose cophasing strategies. We show that the piston, tip and tilt aberrations may need to be as small as 15 nm RMS to allow for diffraction-limited imaging. By taking a co-conception approach, i.e. by taking into account the post-processing capability such as deconvolution, we believe these constraints may be somewhat released. Finally, we show numerical simulation of different solutions allowing the aberrations of the primary mirror segments.; Le volume disponible à bord d'un CubeSat limite la taille de l'ouverture optique à quelques centimètres tout au plus, ce qui limite la résolution au sol atteignable à quelques 3m depuis une orbite basse de 500km. Nous présentons une analyse de performance d'un concept de télescope déployable pour CubeSat. Cette charge utile permettra de tripler la résolution au sol atteignable par un imageur CubeSat, délivrant ainsi une imagerie à très haute résolution depuis une Orbite basse (LEO). Le projet combine le déploiement à grande précision du miroir primaire ainsi que le cophasage de ses pétales en utilisant l'optique active. La charge utile a le potentiel de devenir un nouveau composant sur étagère standardisé, proposé par les concepteurs de CubeSat, pour toutes les missions d'imagerie utilisant les CubeSat ou nanosat. In fine, cette technologie permettra de développer une instrumentation et technologie nouvelles pour les petites plate-formes spatiales, avec un télescope de 30cm. Dans ce papier, nous présentons les spécifications et les différents contributeurs du budget d'erreur qui assurent la performance optique finale. Nous montrons que les erreurs de cophasage en piston, tip et tilt doivent être de l'ordre de quelques dizaines de nanomètres pour assurer la plus haute qualité possible. En utilisant une approche de co-conception, c'est à dire en prenant en compte le post-traitement comme la déconvolution, nous montrons que ces contraintes peuvent être relâchées. Finalement, nous montrons par des simulations numériques les méthodes permettant de mesurer les aberrations du miroir primaire.

International audience; Context. Extremely Large Telescopes have chosen the Pyramid wavefront sensor (PyWFS) over the more widely used Shack-Hartmann WaveFront Sensor (SHWFS) to perform their Single Conjugate Adaptive Optics (SCAO) mode. The PyWFS is a Fourier-filtering based sensor, which has proven to be strongly efficient for astronomical purposes. However, it shows non-linearity behaviors that lead to a reduction of its sensitivity when working around a non-null phase. This effect, called Optical Gains (OG), degrades the performance of the closed loop and prevents accurate correction of Non-Common-Path Aberrations (NCPA). Aims. We aim at computing these so-called OG with a fast and agile technique in order to control the PyWFS measurements for adaptive optics closed-loop systems. Methods. Thanks to a new theoretical description of the PyFWS, which uses a convolutional model to describe the sensor, we analytically predict the behavior of the PyWFS in closed-loop operation. This model allows us to explore the impact of residual phases on the properties of the PyFWS measurements in terms of sensitivity, and associated OG. The proposed method relies on the knowledge of the residual phase statistics and allows to automatically estimate the current OG. End-to-End numerical simulations are used to validate our predictions and test the relevance of our approach. Results. We show that an accurate estimation of the OGs is possible by only using the AO telemetry data to derive statistical information of the turbulence. The method is then fully non-invasive. We further show that by only having an estimation of the current Fried parameter r 0 and the basic system characteristics, OGs can be estimated within 10% accuracy. The proposed method applies to Pyramid WFS, but also to any Fourier-Filtering WFS suffering from OG variations.; Le contexte. Les télescopes extrêmement grands ont choisi le capteur de front d'onde Pyramid (PyWFS) plutôt que le capteur Shack-HartmannWaveFront (SHWFS) plus largement utilisé pour effectuer leur mode SCAO (Single Conjugate Adaptive Optics). Le PyWFS est un capteur basé sur un filtrage de Fourier, qui s'est avéré très efficace à des fins astronomiques. Cependant, il montre des comportements de non-linéarité qui conduisent à une réduction de sa sensibilité lors du travail autour d'une phase non nulle. Cet effet, appelé Gains optiques (OG), dégrade les performances de la boucle fermée et empêche la correction précise des aberrations non communes (NCPA). Objectifs. Nous visons à calculer ces soi-disant OG avec une technique rapide et agile afin de contrôler les mesures PyWFS pour les systèmes en boucle fermée d'optique adaptative. Méthodes. Grâce à une nouvelle description théorique du PyFWS, qui utilise un modèle convolutionnel pour décrire le capteur, nous prédisons analytiquement le comportement du PyWFS en fonctionnement en boucle fermée. Ce modèle nous permet d'explorer l'impact des phases résiduelles sur les propriétés des mesures PyFWS en termes de sensibilité et OG associées. La méthode proposée s'appuie sur la connaissance des statistiques de phase résiduelle et permet d'estimer automatiquement l'OG actuel. Des simulations numériques de bout en bout sont utilisées pour valider nos prédictions et tester la pertinence de nos approches. Résultats. Nous montrons qu'une estimation précise des OG est possible en utilisant uniquement les données de télémétrie AO pour dériver des informations statistiques de la turbulence. La méthode est alors totalement non invasive. Nous montrons en outre qu'en n'ayant qu'une estimation du paramètre de Fried r0 actuel et des caractéristiques de base du système, les OG peuvent être estimés avec une précision de 10%. La méthode proposée s'applique à Pyramid WFS, mais également à tout WFS à filtrage de Fourier subissant des variations OG.

International audience; As already noticed in other telescopes, the presence of large telescope spiders and of a segmented deformable mirror in an Adaptive Optics system leads to pupil fragmentation and may create phase discontinuities. On the ELT telescope, a typical effect is the differential piston, where all disconnected areas of the pupil create their own piston, unseen locally but drastically degrading the final image quality. The poor sensitivity of the Pyramid WFS to differential piston will lead to these modes been badly seen and therefore badly controlled by the adaptive optics (AO) loop. In close loop operation, differential pistons between segments will start to appear and settle around integer values of the average sensing wavelength. These additional differential pistons are artificially injected by the adaptive optics control loop but do not have any real physical origin, contrary to the Low Wind Effect. In an attempt to reduce the impact of unwanted differential pistons that are injected by the AO loop, we propose a novel approach based on the pair-wise coupling of the actuators sitting on the edges of the deformable mirror segments. In this paper, we present the correction principle, its performance in nominal seeing condition, and its robustness relative to changing seeing conditions, wind speed and natural guide star magnitude. We show that the edge actuator coupling is a simple and robust solution and that the additional quadratic error relative to the reference case (i.e. no spiders) is of only 40 nm RMS, well within the requirements for HARMONI.

The next generation of Extremely Large Telescopes (ELTs) for astronomy will rely heavily on the performance of their adaptive optics (AO) systems. Real-time control is at the heart of the critical technologies that will enable telescopes to deliver the best possible science and will require a very significant extrapolation from current AO hardware existing for 4–10 m telescopes. Investigating novel real-time computing architectures and testing their eligibility against anticipated challenges is one of the main priorities of technology development for the ELTs. This paper investigates the suitability of the Intel Xeon Phi, which is a commercial off-the-shelf hardware accelerator. We focus on wavefront reconstruction performance, implementing a straightforward matrix–vector multiplication (MVM) algorithm. We present benchmarking results of the Xeon Phi on a real-time Linux platform, both as a standalone processor and integrated into an existing real-time controller (RTC). Performance of single and multiple Xeon Phis are investigated. We show that this technology has the potential of greatly reducing the mean latency and variations in execution time (jitter) of large AO systems. We present both a detailed performance analysis of the Xeon Phi for a typical E-ELT first-light instrument along with a more general approach that enables us to extend to any AO system size. We show that systematic and detailed performance analysis is an essential part of testing novel real-time control hardware to guarantee optimal science results.

The segmentation of the telescope pupil (by spiders & the segmented M4) create areas of phase isolated by the width of the spiders on the wavefront sensor (WFS), breaking the spatial continuity of the wavefront. The poor sensitivity of the Pyramid WFS (PWFS) to differential piston leads to badly seen and therefore uncontrollable differential pistons. In close loop operation, differential pistons between segments will settle around integer values of the average sensing wavelength. The differential pistons typically range from one to ten times the sensing wavelength and vary rapidly over time, leading to extremely poor performance. In addition, aberrations created by atmospheric turbulence will contain large amounts of differential piston between the segments. Removing piston contribution over each of the DM segments leads to poor performance. In an attempt to reduce the impact of unwanted differential pistons that are injected by the AO correction, we compare three different approaches. We first limit ourselves to only use the information measured by the PWFS, in particular by reducing the modulation. We show that using this information sensibly is important but will not be sufficient. We discuss possible ways of improvement by using prior information. A second approach is based on phase closure of the DM commands and assumes the continuity of the correction wavefront over the entire unsegmented pupil. The last approach is based on the pair-wise slaving of edge actuators and shows the best results. We compare the performance of these methods using realistic end-to-end simulations. We find that pair-wise slaving leads to a small increase of the total wavefront error, only adding between 20-45 nm RMS in quadrature for seeing conditions between 0.45-0.85 arcsec. Finally, we discuss the possibility of combining the different proposed solutions to increase robustness., 12 pages, 15 figures, AO4ELT5 Proceedings, Adaptive Optics for Extremely Large Telescopes 5, Conference Proceeding, Tenerife, Canary Islands, Spain, June 25-30, 2017

Trabajo presentado en SPIE Astronomical Telescopes, celebrado en San Diego (California), del 26 de junio al 1 de julio de 2016, HARMONI is the E-ELT's first light visible and near-infrared integral field spectrograph. It will provide four different spatial scales, ranging from coarse spaxels of 60 × 30 mas best suited for seeing limited observations, to 4 mas spaxels that Nyquist sample the diffraction limited point spread function of the E-ELT at near-infrared wavelengths. Each spaxel scale may be combined with eleven spectral settings, that provide a range of spectral resolving powers (R 3500, 7500 and 20000) and instantaneous wavelength coverage spanning the 0.5 - 2.4 ¿m wavelength range of the instrument. In autumn 2015, the HARMONI project started the Preliminary Design Phase, following signature of the contract to design, build, test and commission the instrument, signed between the European Southern Observatory and the UK Science and Technology Facilities Council. Crucially, the contract also includes the preliminary design of the HARMONI Laser Tomographic Adaptive Optics system. The instrument's technical specifications were finalized in the period leading up to contract signature. In this paper, we report on the first activity carried out during preliminary design, defining the baseline architecture for the system, and the trade-off studies leading up to the choice of baseline.

Study objectives Sleep disordered breathing (SDB) is a highly prevalent condition in high-income countries, with major consequences for cardiopulmonary health, public safety, healthcare utilization, and mortality. However, its prevalence and effect in low- and middle-income countries are less well known. We sought to determine the prevalence, risk factors, and comorbidities of SDB symptoms in four resource-limited settings. Design Cross-sectional analysis of the CRONICAS Cohort, a population-based age- and sex-stratified sample. Setting Four resource-limited settings in Peru varying in altitude, urbanization, and air pollution. Participants There were 2,682 adults aged 35 to 92 y. Measurements and results Self-reported SDB symptoms (habitual snoring, observed apneas, Epworth Sleepiness Scale), sociodemographics, medical history, anthropometrics, spirometry, blood biomarkers were reported. We found a high prevalence of habitual snoring (30.2%, 95% confidence interval [CI] 28.5-32.0%), observed apneas (20.9%, 95% CI 19.4-22.5%) and excessive daytime sleepiness (18.6%, 95% CI 17.1-20.1%). SDB symptoms varied across sites; prevalence and adjusted odds for habitual snoring were greatest at sea level, whereas those for observed apneas were greatest at high altitude. In multivariable analysis, habitual snoring was associated with older age, male sex, body mass index (BMI), and higher socioeconomic status; observed apneas were associated with BMI; and excessive daytime sleepiness was associated with older age, female sex, and medium socioeconomic status. Adjusted odds of cardiovascular disease, depression, and hypertension and total chronic disease burden increased progressively with the number of SDB symptoms. A threefold increase in the odds of having an additional chronic comorbid disease (adjusted odds ratio 3.57, 95% CI 2.18-5.84) was observed in those with all three versus no SDB symptoms. Conclusions Sleep disordered breathing symptoms were highly prevalent, varied widely across four resource-limited settings in Peru, and exhibited strong independent associations with chronic diseases.

Over the past two decades, state and federal education policies have tried to hold schools more accountable for educating students by tying rewards and sanctions to test scores and other measurable outcomes. A common criticism of these policies is that they may induce schools to "game the system" along with — or instead of — making genuine educational improvements. One such strategic response may be to classify low-performing students into categories that are excluded from grade computation in an effort to artificially inflate scores. This article analyzes school responses to an influential accountability-tied voucher program in Florida. The authors find evidence of increased classification into "excluded" categories in failing schools following the program’s inception. Their findings have important implications for New York City’s Progress Reports program and New York’s implementation of the federal No Child Left Behind Act. While these policies were modeled after the Florida program, they contain important design differences that are likely to discourage this type of gaming, although they may encourage other strategic classifications.

Optical aberrations degrade image quality in fluorescence microscopy, including for single-molecule based techniques. These depend on post-processing to localize individual molecules in an image series. Using simulated data, we show the impact of optical aberrations on localization success, accuracy and precision. The peak intensity and the proportion of successful localizations strongly reduces when the aberration strength is greater than 1.0 rad RMS, while the precision of each of those localisations is halved. The number of false-positive localisations exceeded 10% of the number of true-positive localisations at an aberration strength of only ~0.6 rad RMS when using the ThunderSTORM package, but at greater than 1.0 rad RMS with the Radial Symmetry package. In the presence of coma, the localization error reaches 100 nm at ~0.6 rad RMS of aberration strength. The impact of noise and of astigmatism for axial resolution are also considered. Understanding the effect of aberrations is crucial when deciding whether the addition of adaptive optics to a single-molecule microscope could significantly increase the information obtainable from an image series.