Apodization in high-contrast long-slit spectroscopy. Closer, deeper, fainter, cooler

The spectroscopy of faint planetary-mass companions to nearby stars is one of the main challenges that new-generation high-contrast spectro-imagers are going to face. In a previous work we presented a long slit coronagraph (LSC), for which the presence of a slit in the coronagraphic focal plane induces a complex distribution of energy in the Lyot pupil-plane that cannot be easily masked with a binary Lyot stop. To alleviate this concern, we propose to use a pupil apodization to suppress diffraction, creating an apodized long slit coronagraph (ALSC). After describing how the apodization is optimized, we demonstrate its advantages with respect to the CLC in the context of SPHERE/IRDIS long slit spectroscopy (LSS) mode at low-resolution with a 0.12" slit and 0.18" coronagraphic mask. We perform different sets of simulations with and without aberrations, and with and without a slit to demonstrate that the apodization is a more appropriate concept for LSS, at the expense of a significantly reduced throughput (37%) compared to the LSC. Then we perform detailed end-to-end simulations of the LSC and the ALSC that include realistic levels of aberrations to obtain datasets representing 1h of integration time on stars of spectral types A0 to M0 located at 10 pc. We insert spectra of planetary companions at different effective temperatures (Teff) and surface gravities (log g) into the data at angular separations of 0.3" to 1.5" and with contrast ratios from 6 to 18 mag. Using the SD method to subtract the speckles, we show that the ALSC brings a gain in sensitivity of up to 3 mag at 0.3" with respect to the LSC, which leads to a much better spectral extraction below 0.5". In terms of Teff, we demonstrate that at small angular separations the limit with the ALSC is always lower by at least 100K, inducing an increase of sensitivity of a factor up to 1.8 in objects' masses at young ages. [Abridged]Comment: 15 pages, 17 figures. Accepted for publication in A&

Calibration of quasi-static aberrations in exoplanet direct-imaging instruments with a Zernike phase-mask sensor

Context. Several exoplanet direct imaging instruments will soon be in operation. They use an extreme adaptive optics (XAO) system to correct the atmospheric turbulence and provide a highly-corrected beam to a near-infrared (NIR) coronagraph for starlight suppression. The performance of the coronagraph is however limited by the non-common path aberrations (NCPA) due to the differential wavefront errors existing between the visible XAO sensing path and the NIR science path, leading to residual speckles in the coronagraphic image. Aims. Several approaches have been developed in the past few years to accurately calibrate the NCPA, correct the quasi-static speckles and allow the observation of exoplanets at least 1e6 fainter than their host star. We propose an approach based on the Zernike phase-contrast method for the measurements of the NCPA between the optical path seen by the visible XAO wavefront sensor and that seen by the near-IR coronagraph. Methods. This approach uses a focal plane phase mask of size {\lambda}/D, where {\lambda} and D denote the wavelength and the telescope aperture diameter, respectively, to measure the quasi-static aberrations in the upstream pupil plane by encoding them into intensity variations in the downstream pupil image. We develop a rigorous formalism, leading to highly accurate measurement of the NCPA, in a quasi-linear way during the observation. Results. For a static phase map of standard deviation 44 nm rms at {\lambda} = 1.625 {\mu}m (0.026 {\lambda}), we estimate a possible reduction of the chromatic NCPA by a factor ranging from 3 to 10 in the presence of AO residuals compared with the expected performance of a typical current-generation system. This would allow a reduction of the level of quasi-static speckles in the detected images by a factor 10 to 100 hence, correspondingly improving the capacity to observe exoplanets.Comment: 11 pages, 14 figures, A&A accepted, 2nd version after language-editor correction

In situ observation of stress relaxation in epitaxial graphene

Upon cooling, branched line defects develop in epitaxial graphene grown at high temperature on Pt(111) and Ir(111). Using atomically resolved scanning tunneling microscopy we demonstrate that these defects are wrinkles in the graphene layer, i.e. stripes of partially delaminated graphene. With low energy electron microscopy (LEEM) we investigate the wrinkling phenomenon in situ. Upon temperature cycling we observe hysteresis in the appearance and disappearance of the wrinkles. Simultaneously with wrinkle formation a change in bright field imaging intensity of adjacent areas and a shift in the moire spot positions for micro diffraction of such areas takes place. The stress relieved by wrinkle formation results from the mismatch in thermal expansion coefficients of graphene and the substrate. A simple one-dimensional model taking into account the energies related to strain, delamination and bending of graphene is in qualitative agreement with our observations.Comment: Supplementary information: S1: Photo electron emission microscopy and LEEM measurements of rotational domains, STM data of a delaminated bulge around a dislocation. S2: Movie with increasing brightness upon wrinkle formation as in figure 4. v2: Major revision including new experimental dat

Construction of an integrated consensus map of the Apple genome based on four mapping populations

An integrated consensus genetic map for apple was constructed on the basis of segregation data from four genetically connected crosses (C1¿=¿Discovery × TN10-8, C2¿=¿Fiesta × Discovery, C3¿=¿Discovery × Prima, C4¿=¿Durello di Forli × Fiesta) with a total of 676 individuals using CarthaGene® software. First, integrated female¿male maps were built for each population using common female¿male simple sequence repeat markers (SSRs). Then, common SSRs over populations were used for the consensus map integration. The integrated consensus map consists of 1,046 markers, of which 159 are SSR markers, distributed over 17 linkage groups reflecting the basic chromosome number of apple. The total length of the integrated consensus map was 1,032 cM with a mean distance between adjacent loci of 1.1 cM. Markers were proportionally distributed over the 17 linkage groups (¿ 2¿=¿16.53, df¿=¿16, p¿=¿0.41). A non-uniform marker distribution was observed within all of the linkage groups (LGs). Clustering of markers at the same position (within a 1-cM window) was observed throughout LGs and consisted predominantly of only two to three linked markers. The four integrated female¿male maps showed a very good colinearity in marker order for their common markers, except for only two (CH01h01, CH05g03) and three (CH05a02z, NZ02b01, Lap-1) markers on LG17 and LG15, respectively. This integrated consensus map provides a framework for performing quantitative trait locus (QTL) detection in a multi-population design and evaluating the genetic background effect on QTL expression

Laboratory validation of the dual-zone phase mask coronagraph in broadband light at the high-contrast imaging THD-testbed

Specific high contrast imaging instruments are mandatory to characterize circumstellar disks and exoplanets around nearby stars. Coronagraphs are commonly used in these facilities to reject the diffracted light of an observed star and enable the direct imaging and spectroscopy of its circumstellar environment. One important property of the coronagraph is to be able to work in broadband light. Among several proposed coronagraphs, the dual-zone phase mask coronagraph is a promising solution for starlight rejection in broadband light. In this paper, we perform the first validation of this concept in laboratory. First, we recall the principle of the dual-zone phase mask coronagraph. Then, we describe the high-contrast imaging THD testbed, the manufacturing of the components and the quality-control procedures. Finally, we study the sensitivity of our coronagraph to low-order aberrations (inner working angle and defocus) and estimate its contrast performance. Our experimental broadband light results are compared with numerical simulations to check agreement with the performance predictions. With the manufactured prototype and using a dark hole technique based on the self-coherent camera, we obtain contrast levels down to $2\,10^{-8}$ between 5 and 17$\,\lambda_0/D$ in monochromatic light (640 nm). We also reach contrast levels of $4\,10^{-8}$ between 7 and 17$\lambda_0/D$ in broadband ($\lambda_0=675$ nm, $\Delta\lambda=250$ nm and $\Delta\lambda / \lambda_0 = 40$ %), which demonstrates the excellent chromatic performance of the dual-zone phase mask coronagraph. The performance reached by the dual-zone phase mask coronagraph is promising for future high-contrast imaging instruments that aim at detecting and spectrally characterizing old or light gaseous planets.Comment: 9 pages, 16 figure

Effet du système de production sur l'âge au premier vêlage chez la vache Borgou au Bénin. – Etude rétrospective

Effect of Production Systems on Age at First Calving on Borgou Cow in Benin. -Retrospective Study. Data collected from "Monastère de l'Etoile" in department of Borgou in Benin, were used to evaluate the age at first calving of Borgou cow under two different production systems, i.e., extensive and semi-intensive. Production systems significantly affect age at first calving (p< 0.01): cow represented in the extensive system had a higher age at first calving than those presented in the semi-intensive system

Errors recruit both cognitive and emotional monitoring systems: Simultaneous intracranial recordings in the dorsal anterior cingulate gyrus and amygdala combined with fMRI

We studied error monitoring in a human patient with unique implantation of depth electrodes in both the left dorsal cingulate gyrus and medial temporal lobe prior to surgery. The patient performed a speeded go/nogo task and made a substantial number of commission errors (false alarms). As predicted, intracranial Local Field Potentials (iLFPs) in dorsal anterior cingulate indexed the detection of errors, showing an early differential activity around motor execution for false alarms, relative to correct responses (either hits or correct inhibitions). More surprisingly, we found that the left amygdala also participated to error monitoring (although no emotional stimuli were used), but with a very different neurophysiological profile as compared with the dorsal cingulate cortex. Amygdala iLFPs showed a precise and reproducible temporal unfolding, characterized by an early monophasic response for correct hits around motor execution, which was delayed by approximately 300ms for errors (even though actual RTs were almost identical in these two conditions). Moreover, time-frequency analyses demonstrated a reliable and transient coupling in the theta band around motor execution between these two distant regions. Additional fMRI investigation in the same patient confirmed a differential involvement of the dorsal cingulate cortex vs. amygdala in error monitoring during this go/nogo task. Finally, these intracranial results for the left amygdala were replicated in a second patient with intracranial electrodes in the right amygdala. Altogether, these results suggest that the amygdala may register the motivational significance of motor actions on a trial-by-trial basis, while the dorsal anterior cingulate cortex may provide signals concerning failures of cognitive control and behavioral adjustment. More generally, these data shed new light on neural mechanisms underlying self-monitoring by showing that even "simple" motor actions recruit not only executive cognitive processes (in dorsal cingulate) but also affective processes (in amygdala)

Interface-engineered hole doping in Sr2IrO4/LaNiO3 heterostructure

The relativistic Mott insulator Sr2IrO4 driven by large spin-orbit interaction is known for the Jeff = 1/2 antiferromagnetic state which closely resembles the electronic structure of parent compounds of superconducting cuprates. Here, we report the realization of hole-doped Sr2IrO4 by means of interfacial charge transfer in Sr2IrO4/LaNiO3 heterostructures. X-ray photoelectron spectroscopy on Ir 4f edge along with the X-ray absorption spectroscopy at Ni L2 edge confirmed that 5d electrons from Ir sites are transferred onto Ni sites, leading to markedly electronic reconstruction at the interface. Although the Sr2IrO4/LaNiO3 heterostructure remains non-metallic, we reveal that the transport behavior is no longer described by the Mott variable range hopping mode, but by the Efros-Shklovskii model. These findings highlight a powerful utility of interfaces to realize emerging electronic states of the Ruddlesden-Popper phases of Ir-based oxides.Comment: 9 pages including 3 figures and reference