Self-coherent camera as a focal plane wavefront sensor: simulations

Direct detection of exoplanets requires high dynamic range imaging. Coronagraphs could be the solution, but their performance in space is limited by wavefront errors (manufacturing errors on optics, temperature variations, etc.), which create quasi-static stellar speckles in the final image. Several solutions have been suggested for tackling this speckle noise. Differential imaging techniques substract a reference image to the coronagraphic residue in a post-processing imaging. Other techniques attempt to actively correct wavefront errors using a deformable mirror. In that case, wavefront aberrations have to be measured in the science image to extremely high accuracy. We propose the self-coherent camera sequentially used as a focal-plane wavefront sensor for active correction and differential imaging. For both uses, stellar speckles are spatially encoded in the science image so that differential aberrations are strongly minimized. The encoding is based on the principle of light incoherence between the hosting star and its environment. In this paper, we first discuss one intrinsic limitation of deformable mirrors. Then, several parameters of the self-coherent camera are studied in detail. We also propose an easy and robust design to associate the self-coherent camera with a coronagraph that uses a Lyot stop. Finally, we discuss the case of the association with a four-quadrant phase mask and numerically demonstrate that such a device enables the detection of Earth-like planets under realistic conditions. The parametric study of the technique lets us believe it can be implemented quite easily in future instruments dedicated to direct imaging of exoplanets.Comment: 15 pages, 14 figures, accepted in A&A (here is the final version

Les marchés du travail dans la crise

Principale conséquence de la crise économique que nous traversons, la situation du marché du travail s’est fortement dégradée dans l’ensemble des grands pays développés. À l’exception de l’Allemagne, le rythme de hausse du chômage au cours de cet épisode récessif a été deux fois plus violent que celui observé au cours des « petites » crises précédentes. Ce fort impact sur le chômage masque pourtant une relative résistance face à un choc de production d’une ampleur sans précédent depuis les années 1930. Cette résistance du chômage tient d’abord à l’impact encore faible et inachevé de la crise sur l’emploi. Elle s’explique aussi par les comportements d’activité qui amortissent traditionnellement les chocs d’emploi du fait du découragement induit d’une partie de la population active. Nous détaillons la réaction des marchés du travail dans sept grands pays : Allemagne, France, Italie, Espagne, Royaume-Uni, États-Unis et Japon. Dans un premier temps, nous montrons qu’à l’exception de l’Espagne et des États-Unis, l’ajustement de l’emploi n’y est pas achevé. Puis, nous montrons que les écarts d’ajustement de l’emploi s’expliquent en partie par le recours à la flexibilité interne des entreprises (modification du temps de travail et des coûts salariaux). Enfin, nous analysons l’impact de la dégradation du marché de l’emploi sur le chômage en étudiant les comportements d’activité. Il convient toutefois de garder à l’esprit que la crise est loin d’être terminée, et que les chiffres disponibles sont encore provisoires. Ce n’est qu’à la fin du cycle que l’on saura si les marchés du travail ont réagi différemment à la crise actuelle.As a consequence of the economic crisis, the labor market situation has deteriorated sharply in major developed countries. However, the increase in unemployment masks a relative resistance to an outstanding production shock. This resistance is primarily due to the low and incomplete adjustment of employment. It is also related to changes in activity rates that traditionally absorb employment shocks because of workers discouragement. We detail labor market reaction in seven major countries. We first show that, except for Spain and the United States, the employment adjustment is not finished yet. Then, we show that differences in employment adjustment can be partly explained by internal flexibility (changes in working time and labor costs). Finally, we analyze how the deterioration of labor market impacts unemployment by studying activity behaviors

An evaluation of word usage practice lessons

Thesis (M.A.)--Boston Universit

Spatial Patterns of Iron- and Methane-Oxidizing Bacterial Communities in an Irregularly Flooded, Riparian Wetland

Iron- and methane-cycling are important processes in wetlands with one connected to plant growth and the other to greenhouse gas emission, respectively. In contrast to acidic habitats, there is scarce information on the ecology of microbes oxidizing ferrous iron at circumneutral pH. The latter is mainly due to the lack of isolated representatives and molecular detection techniques. Recently, we developed PCR–DGGE and qPCR assays to detect and enumerate Gallionella-related neutrophilic iron-oxidizers (Ga-FeOB) enabling the assessment of controlling physical as well as biological factors in various ecosystems. In this study, we investigated the spatial distribution of Ga-FeOB in co-occurrence with methane-oxidizing bacteria (MOB) in a riparian wetland. Soil samples were collected at different spatial scales (ranging from meters to centimeters) representing a hydrological gradient. The diversity of Ga-FeOB was assessed using PCR–DGGE and the abundance of both Ga-FeOB and MOB by qPCR. Geostatistical methods were applied to visualize the spatial distribution of both groups. Spatial distribution as well as abundance of Ga-FeOB and MOB was clearly correlated to the hydrological gradient as expressed in moisture content of the soil. Ga-FeOB outnumbered the MOB subgroups suggesting their competitiveness or the prevalence of Fe2+ over CH4 oxidation in this floodplain

Change in Right Inferior Longitudinal Fasciculus Integrity Is Associated With Naming Recovery in Subacute Poststroke Aphasia

Background. Despite progress made in understanding functional reorganization patterns underlying recovery in subacute aphasia, the relation between recovery and changes in white matter structure remains unclear. Objective. To investigate changes in dorsal and ventral language white matter tract integrity in relation to naming recovery in subacute poststroke aphasia. Methods. Ten participants with aphasia after left-hemisphere stroke underwent language testing and diffusion tensor imaging twice within 3 months post onset, with a 1-month interval between sessions. Deterministic tractography was used to bilaterally reconstruct the superior longitudinal fasciculus (SLF), inferior fronto-occipital fasciculus (IFOF), inferior longitudinal fasciculus (ILF), middle longitudinal fasciculus (MdLF), and uncinate fasciculus (UF). Per tract, the mean fractional anisotropy (FA) was extracted as a measure of microstructural integrity. Naming accuracy was assessed with the Boston Naming Test (BNT). Correlational analyses were performed to investigate the relationship between changes in FA values and change in BNT score. Results. A strong positive correlation was found between FA change in the right ILF within the ventral stream and change on the BNT (r = 0.91, P <.001). An increase in FA in the right ILF was associated with considerable improvement of naming accuracy (range BNT change score: 12-14), a reduction with limited improvement or slight deterioration. No significant correlations were found between change in naming accuracy and FA change in any of the other right or left ventral and dorsal language tracts. Conclusions. Naming recovery in subacute aphasia is associated with change in the integrity of the right ILF

Indice Generale

Melt viscosity is a key indicator of product quality in polymer extrusion processes. However, real time monitoring and control of viscosity is difficult to achieve. In this article, a novel “soft sensor” approach based on dynamic gray-box modeling is proposed. The soft sensor involves a nonlinear finite impulse response model with adaptable linear parameters for real-time prediction of the melt viscosity based on the process inputs; the model output is then used as an input of a model with a simple-fixed structure to predict the barrel pressure which can be measured online. Finally, the predicted pressure is compared to the measured value and the corresponding error is used as a feedback signal to correct the viscosity estimate. This novel feedback structure enables the online adaptability of the viscosity model in response to modeling errors and disturbances, hence producing a reliable viscosity estimate. The experimental results on different material/die/extruder confirm the effectiveness of the proposed “soft sensor” method based on dynamic gray-box modeling for real-time monitoring and control of polymer extrusion processes

Interventions to enhance adherence to medications in patients with heart failure: a systematic review

First paragraph: Prognosis remains poor for patients with chronic heart failure (CHF), despite improvements in the prevention and treatment of heart failure over the last 25 years. Recent estimates indicate that the median survival after a first episode of heart failure is 2.3 years for men and 1.8 years for women. It is suggested that the improvements in outcomes that have been achieved can be partly explained by increases in prescribing rates of medications such as angiotensin-converting enzyme inhibitors, &beta;-blockers, and spironolactone over this period. Although the evidence on medication efficacy for certain subgroups of patients with CHF is clear, there are also compelling data showing that many of these patients do not take their medications as prescribed by health care providers. This "nonadherence" to medication therefore remains a significant barrier to enhancing the effectiveness of existing treatments