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

Supplementation of Cattle with Rock Phosphate and Urea Treated Straw to Improve Manure Quality and Crop Yields in the Sahel Zone of Senegal

Mineral deficiencies are a major constraint in improving animal production and crop yield in the Sahel zone (Cissé et al., 1996). Millet (Pennisetum glaucum) and groundnut (Arachis hypogaea,) are two major food and cash crops in this zone. The purpose of this study was to assess effects of supplementing grazing cattle with rock phosphate and nitrogen enriched diets on animal performances, and the effects of the application of their manure on crop yield in a pearl millet-groundnut rotational system located in N Senegal

Ultrasound-assisted adsorption of Methyl Parathion using commercial Granular Activated Carbon from aqueous solution

The removal of Methyl parathion (MP) by ultrasound-assisted adsorption using commercial Granular Activated Carbon (GAC) was studied. The effect of sonicate time on the adsorption were studied using the batch technique. The adsorption kinetic data were analyzed using the Pseudo First Order (PFO) and Pseudo Second Order (PSO) models. For kinetic study, the adsorption process fitted the PSO model. Three adsorption isotherms namely the Langmuir, Freundlich and Redlich–Peterson isotherms in their non-linear forms were applied to the adsorption equilibrium data. Both the Langmuir and Redlich–Peterson models were found to fit the adsorption isotherm data well, but the Redlich– Peterson model was better. The monolayer adsorption capacity, qm, was found to be 20.20 mg g-1. It can be concluded that the commercial GAC is an efficient adsorbent for the removal of MP from aqueous solution via ultrasound-assisted adsorption. Attempt to explain the reactivity of MP on GAC by theoretical calculations was made

No effect of subthalamic deep brain stimulation on metacognition in Parkinson’s disease

Deep brain stimulation of the subthalamic nucleus (STN-DBS) is a powerful treatment in Parkinson’s disease (PD), which provides a positive effect on motor symptoms although the way it operates on high cognitive processes such as metacognition remains unclear. To address this issue, we recorded electroencephalogram (EEG) of PD patients treated with STN-DBS that performed a reversal learning (RL) paradigm endowed with metacognitive self-assessment. We considered two stimulation conditions, namely DBS-ON (stimulation on) and DBS-OFF (stimulation off), and focused our EEG-analysis on the frontal brain region due to its involvement on high cognitive processes. We found a trend towards a significant difference in RL ability between stimulation conditions. STN-DBS showed no effect on metacognition, although a significant association between accuracy and decision confidence level held for DBS OFF, but not in the case of DBS ON. In summary, our study revealed no significant effect of STN-DBS on RL or metacognition

Oxidation of graphene on metals

We use low-energy electron microscopy to investigate how graphene is removed from Ru(0001) and Ir(111) by reaction with oxygen. We find two mechanisms on Ru(0001). At short times, oxygen reacts with carbon monomers on the surrounding Ru surface, decreasing their concentration below the equilibrium value. This undersaturation causes a flux of carbon from graphene to the monomer gas. In this initial mechanism, graphene is etched at a rate that is given precisely by the same non-linear dependence on carbon monomer concentration that governs growth. Thus, during both growth and etching, carbon attaches and detaches to graphene as clusters of several carbon atoms. At later times, etching accelerates. We present evidence that this process involves intercalated oxygen, which destabilizes graphene. On Ir, this mechanism creates observable holes. It also occurs mostly quickly near wrinkles in the graphene islands, depends on the orientation of the graphene with respect to the Ir substrate, and, in contrast to the first mechanism, can increase the density of carbon monomers. We also observe that both layers of bilayer graphene islands on Ir etch together, not sequentially.Comment: 15 pages, 10 figures. Manuscript revised to improve discussion, following referee comments. Accepted for publication in Journal of Physical Chemistry C, Feb. 11, 201

Comportement des dromadaires sur patures Sahelien et Subhumide au Mali : 2. Especes vegetales et quantites de fourrage ingerees

Trois expériences ont été conduites entre 2014 et 2015 sur 12 dromadaires mâles adultes à Niono et 12 à Sotuba pour identifier les espèces broutées et la quantité de matière sèche ingérée correspondante en zones sahélienne et subhumide. Les données ont été collectées par suivi quotidien de 4 dromadaires porteurs de sac de collecte de fèces choisis au hasard, conduits avec le reste du troupeau durant 12 jours. A Niono, 32 espèces végétales ont été broutées et 71 espèces à Sotuba. A Niono, les espèces les plus broutées ont été Acacia seyal (19 %), Acacia senegal 14,8%), Balanites aegyptiaca (12,6 %) pour les ligneux et Zornia glochidiata (12,6 %) et Schoenefeldia gracilis (6,1 %) pour les graminées. A Sotuba, ce sont Ziziphus mauritiana (14,9 %), Vitellaria paradoxum (10,5 %) et les graminées Cassia tora (7,4 %) et Hiptis suaveolens (6,2 %). Dans le menu figuraient les feuilles, les rameaux, les fleurs et les fruits des espèces végétales consommées. Le taux moyen de protéines de l’ingéré a été de 13,3 % à Niono contre 8,7 % à Sotuba. La digestibilité de la matière sèche a été de 47,9 % à Niono contre 41,2 % à Sotuba. La teneur en protéines digestibles a été de 66,8 ± 0,8 g/kg MS à Niono contre 62,0 ± 0,7 g/kg MS à Sotuba. La quantité de matière sèche ingérée a été de 5,6 ± 0,2 kg à Niono et 5,1 ± kg à Sotuba. La connaissance de ces informations permettra de mieux organiser la complémentation alimentaire des dromadaires afin d’optimiser  leurs productions en zones sahélienne et subhumide du Mali. Mots clés : dromadaires, ingestion pâturage, sahel, subhumide, Mali English Title: Dromedary behaviour on Sahelian and subhumid pasture of Mali: 2. Plant species and feed intake Three experiments were conducted on 30 adult male camels to identify species grazed and the amount of dry matter ingested in the Sahelian (Niono) and sub-humid (Sotuba), zones during the rainy, cold dry and hot dry, seasons. Data were collected by monitoring 4 camels carrying faeces collection bags conducted with the rest of the herd. In Niono, 32 plant species were grazed and 71 species in Sotuba. The menu included leaves, twigs, flowers and fruits of consumed plant species. The average protein level of ingest was 13.3% in Niono and 8.7% in Sotuba. The digestibility of the material was 47.9% in Niono and 41.2% in Sotuba. The digestible protein content was 66.8 ± 0.8 g / kg of dry matter (DM) at Niono and 62.0 ± 0.7 g / kg DM at Sotuba. The amount of dry matter ingested was 5.6 ± 0.2 kg at Niono and 5.1 ± kg at Sotuba. Knowledge of this information is a key element to better organize animal feed supplementation in order to optimize camel production in the sahelian and sub-humid zones of Mali. Keywords: camels, grazing ingestion, Sahel, subhumid, Mal

ORAL LESIONS OF HIV-INFECTED CHILDREN IN WEST AFRICA IN THE ERA OF ANTIRETROVIRAL TREATMENTS

Oral Communication presented at the "Forum des Jeunes Chercheurs", Brest (France) 2011

Fermi surfaces of single layer dielectrics on transition metals

Single sheets of hexagonal boron nitride on transition metals provide a model system for single layer dielectrics. The progress in the understanding of h-BN layers on transition metals of the last 10 years are shortly reviewed. Particular emphasis lies on the boron nitride nanomesh on Rh(111), which is a corrugated single sheet of h-BN, where the corrugation imposes strong lateral electric fields. Fermi surface maps of h-BN/Rh(111) and Rh(111) are compared. A h-BN layer on Rh(111) introduces no new bands at the Fermi energy, which is expected for an insulator. The lateral electric fields of h-BN nanomesh violate the conservation law for parallel momentum in photoemission and smear out the momentum distribution curves on the Fermi surface.Comment: 14 pages, 6 figures, 1 table, 1 equation, Accepted for publication in the Special Surface Science issue in honor of Gerhard Ertl's Nobel Priz

Water Absorption of Poly(methyl methacrylate) Measured by Vertical Interference Microscopy

PMMA (poly(methyl methacrylate)) is widely used to prepare orthopedic cements. They are in direct contact with cells and body fluids. PMMA, despite its hydrophobic nature, can absorb ?2% w/w water. We have evaluated by vertical interference microscopy if water absorption can produce a significant swelling in different types of PMMA blocks: pure, with a plasticizer, with a cross-linker, and in two types of commercial bone cements. Graphite rods which do not swell in water were used as internal standard. Hardness, indentation modulus, plastic, and elastic works were determined by nanoindentation under a 25mN fixed force. Vertical interference microscopy was used to image the polymer in the dry state and hydrated states (after 24 h in distilled water). On the surface of the polished polymers (before and after hydration), we measured roughness by the fractal dimension, the swelling in the vertical and the lateral directions. For each polymer block, four images were obtained and values were averaged. Comparison and standardization of the images in the dry and hydrated states were done with Matlab software. The average value measured on the graphite rod between the two images (dried and hydrated) was used for standardization of the images which were visualized in 3D. After grinding, a small retraction was noticeable between the surface of the rod and the polymers. A retraction ring was also visible around the graphite rod. After hydration, only the pure PMMA and bone cements had a significant swelling in the vertical direction. The presence of polymer beads in the cements limited the swelling in the lateral direction. Swelling parameters correlated with the nanoindentation data. PMMA can swell by absorbing a small amount of water and this induces a swelling that varies with the polymer composition and particle inclusions

Effects of proton versus photon irradiation on (lymph) angiogenic, inflammatory, proliferative and anti-tumor immune responses in head and neck squamous cell carcinoma

International audienceThe proximity of organs at risk makes the treatment of head and neck squamous cell carcinoma (HNSCC) challenging by standard radiotherapy. The higher precision in tumor targeting of proton (P) therapy could promote it as the treatment of choice for HNSCC. Besides the physical advantage in dose deposition, few is known about the biological impact of P versus photons (X) in this setting. To investigate the comparative biological effects of P versus X radiation in HNSCC cells, we assessed the relative biological effectiveness (RBE), viability, proliferation and mRNA levels for genes involved in (lymph)angiogenesis, inflammation, proliferation and anti-tumor immunity. These parameters, particularly VEGF-C protein levels and regulations, were documented in freshly irradiated and/or long-term surviving cells receiving low/high-dose, single (SI)/multiple (MI) irradiations with P/X. The RBE was found to be 1.1 Key (lymph)angiogenesis and inflammation genes were downregulated (except for vegf-c) after P and upregulated after X irradiation in MI surviving cells, demonstrating a more favorable profile after P irradiation. Both irradiation types stimulated vegf-c promoter activity in a NF-κB-dependent transcriptional regulation manner, but at a lesser extent after P, as compared to X irradiation, which correlated with mRNA and protein levels. The cells surviving to MI by P or X generated tumors with higher volume, anarchic architecture and increased density of blood vessels. Increased lymphangiogenesis and a transcriptomic analysis in favor of a more aggressive phenotype were observed in tumors generated with X-irradiated cells. Increased detection of lymphatic vessels in relapsed tumors from patients receiving X radiotherapy was consistent with these findings. This study provides new data about the biological advantage of P, as compared to X irradiation. In addition to its physical advantage in dose deposition, P irradiation may help to improve treatment approaches for HNSCC