High energy blazars spectroscopy with X-Shooter on the VLT

We present results of observations in the UV to near-IR range for eight blazars, three of which have been recently discovered at Very High Energies (VHE) and five appearing as interesting candidates for VHE {\gamma}-ray detection. We focus in this paper on the search for their redshifts, which are unknown or considered as uncertain.Comment: 4 pages, 8 figures, to appear in the proceedings of the 5th International Symposium on High-Energy Gamma-Ray Astronomy (Gamma2012), July 9-13, 2012, Heidelberg, German

Earth rotation prevents exact solid-body rotation of fluids in the laboratory

International audience–We report direct evidence of a secondary flow excited by the Earth rotation in a water-filled spherical container spinning at constant rotation rate. This so-called tilt-over flow essentially consists in a rotation around an axis which is slightly tilted with respect to the rotation axis of the sphere. In the astrophysical context, it corresponds to the flow in the liquid cores of planets forced by precession of the planet rotation axis, and it has been proposed to contribute to the generation of planetary magnetic fields. We detect this weak secondary flow using a particle image velocimetry system mounted in the rotating frame. This secondary flow consists in a weak rotation, thousand times smaller than the sphere rotation, around a horizontal axis which is stationary in the laboratory frame. Its amplitude and orientation are in quantitative agreement with the theory of the tilt-over flow excited by precession. These results show that setting a fluid in a perfect solid body rotation in a laboratory experiment is impossible — unless tilting the rotation axis of the experiment parallel to the Earth rotation axis. Introduction. – There are few examples of fluid mechanics experiments at the laboratory scale in which the Earth's Coriolis force has a measurable influence. Such experiments may be considered as fluid analogues to the Foucault pendulum. The most popular instance is certainly the drain of a bathtube vortex [1]. Although this is the subject of common misconception, it is actually possible to detect the influence of the Earth's rotation on the vortex, but only under extremely careful experimental conditions, far from the everyday experience [2]. Thermal convection is another example, in which a slow drift of the large-scale flow due to the Earth rotation has been detected in very controlled systems [3, 4]. In this letter we describe an experiment which may be considered as the most simple fluid Foucault pendulum: it consists in a volume of water enclosed in a spherical container spinning at constant rotation rate Ω 0 (fig. 1). After a transient known as spin-up, the water is expected to rotate as a solid body at the same rate Ω 0 [5]. The (a

Modélisation de Scènes Naturelles à Partir de Séquences Vidéos Multi-vue plus Profondeur (MVD)

National audienceDans cet article, un schéma de modélisation de séquences Multi-vues Vidéo plus profondeur (MVD) est présenté. Le but est de réduire la redondance de profondeur et de texture présentes dans les séquences MVD. Pour ce faire, la fusion de cartes de profondeurs utilisant une représentation volumétrique est proposée. Les voxels sont "carvés" itérativement pour chaque vue en utilisant la technique de traçage de rayons (ray tracing). La surface fusionnée est extraite à partir de cette représentation en utilisant l'algorithme de Marching Cubes. Finalement, le problème de plaquage des textures sur cette surface résultante est abordé. L'algorithme proposé sélectionne parmi toutes les textures le meilleur candidat pour texturer un triangle de la surface résultante. Ce choix est fait en utilisant une métrique dite de photocohérence. Les tests et les résultats sont fournis pour des images fixes en utilisant les séquences MVD usuelles

MULTI-TEXTURING 3D MODELS: HOW TO CHOOSE THE BEST TEXTURE?

International audienceIn this article, the impact of 2D based approaches for multi-texturing 3D models using real images is studied. While conventional 3D based approaches assign the best texture for each mesh triangle according to geometric criteria such as triangle orientation or triangle area, 2D based approaches tend to minimize the distortion between the rendered views and the original ones. Evaluation of the two strategies is performed on real scenes for two image sequences and results are provided using the PSNR metric. Moreover, an improvement of the image-based approach is proposed for texturing partially visible triangles

Space Carving MVD Sequences for Modeling Natural 3D Scenes

International audienceThis paper presents a 3D modeling system designed for Multi-view Video plus Depth (MVD) sequences. The aim is to remove redundancy in both texture and depth information present in the MVD data. To this end, a volumetric framework is employed in order to merge the input depth maps. Hereby a variant of the Space Carving algorithm is proposed. Voxels are iteratively carved by ray-casting from each view, until the 3D model be geometrically consistent with every input depth map. A surface mesh is then extracted from this volumetric representation thanks to the Marching Cubes algorithm. Subsequently, to address the issue of texture modeling, a new algorithm for multi-texturing the resulting surface is presented. This algorithm selects from the set of input images the best texture candidate to map a given mesh triangle. The best texture is chosen according to a photoconsistency metric. Tests and results are provided using still images from usual MVD test-sequences

Spectroscopy of High Energy BL Lac Objects with X-shooter on the VLT

Context. The study of BL Lac objects (BLL) detected in gamma-rays gives insights on the acceleration mechanisms in play in such systems and is also a valuable tool to constrain the density of the extragalactic background light. As their spectra are dominated by the non-thermal emission of the jet and the spectral features are weak and narrow in the optical domain, measuring their redshift is challenging. However such a measure is fundamental as it allows a firm determination of the distance and luminosity of the source, and therefore a consistent model of its emission. Aims. Measurement of the redshift of BLL detected in gamma-rays and determination of global properties of their host galaxies. Methods. We observed a sample of eight BLL (KUV 00311-1938, PKS 0447-439, PKS 0301-243, BZB J0238-3116, BZB J0543-5532, BZB J0505+0415, BZB J0816-1311 and RBS 334) with the X-shooter spectrograph installed at the ESO Very Large Telescope in order to take advantage of its unprecedented wavelength coverage and of its resolution about 5 times higher than generally used in such studies. We extracted UVB to NIR spectra that we then corrected for telluric absorption and calibrated in flux. We systematically searched for spectral features. When possible, we determined the contribution of the host galaxy to the overall emission. Results. Of the eight BLL, we measured the redshift of five of them and determined lower limits for two through the detection of intervening systems. All seven of these objects have redshifts greater than 0.2. In two cases, we refuted redshift values reported in other publications. Through careful modelling, we determined the magnitude of the host galaxies. In two cases, the detection of emission lines allowed to provide hints on the overall properties of the gas in the host galaxies.Comment: 19 pages, 10 figures, 7 tables, in press on A&

A preliminary study of phosphodiesterases and adenylyl cyclase signaling pathway on red blood cell deformability of sickle cell patients

Sickle cell disease (SCD) is an inherited hemoglobinopathy characterized by chronic anemia, intravascular hemolysis, and the occurrence of vaso-occlusive crises due to the mechanical obstruction of the microcirculation by poorly deformable red blood cells (RBCs). RBC deformability is a key factor in the pathogenesis of SCD, and is affected by various factors. In this study, we investigated the effects of adenylyl cyclase (AC) signaling pathway modulation and different phosphodiesterase (PDE) modulatory molecules on the deformability and mechanical stress responses of RBC from SCD patients (HbSS genotype) by applying 5 Pa shear stress with an ektacytometer (LORRCA). We evaluated RBC deformability before and after the application of shear stress. AC stimulation with Forskolin had distinct effects on RBC deformability depending on the application of 5 Pa shear stress. RBC deformability was increased by Forskolin before shear stress application but decreased after 5 Pa shear stress. AC inhibition with SQ22536 and protein kinase A (PKA) inhibition with H89 increased RBC deformability before and after the shear stress application. Non-selective PDE inhibition with Pentoxifylline increased RBC deformability. However, modulation of the different PDE types had distinct effects on RBC deformability, with PDE1 inhibition by Vinpocetine increasing deformability while PDE4 inhibition by Rolipram decreased RBC deformability after the shear stress application. The effects of the drugs varied greatly between patients suggesting some could benefit from one drug while others not. Developing drugs targeting the AC signaling pathway could have clinical applications for SCD, but more researches with larger patient cohorts are needed to identify the differences in the responses of sickle RBCs

Experimental Observation of Spatially Localized Dynamo Magnetic Fields

International audienceWe report the first experimental observation of a spatially localized dynamo magnetic field, a common feature of astrophysical dynamos and convective dynamo simulations. When the two propellers of the von Ka ́rma ́n sodium experiment are driven at frequencies that differ by 15%, the mean magnetic field's energy measured close to the slower disk is nearly 10 times larger than the one close to the faster one. This strong localization of the magnetic field when a symmetry of the forcing is broken is in good agreement with a prediction based on the interaction between a dipolar and a quadrupolar magnetic mode

Support clubs for children and youth in Haiti living with HIV: A case study

In Haiti, where an estimated 3,000 children and youth are receiving antiretroviral therapy (ART), Caris Foundation, with funding from the United States President’s Emergency Plan for AIDS Relief (PEPFAR) through the United States Agency for International Development (USAID), provides hospital-linked psychosocial support groups, known as Kids Clubs, for young people ages nine and older. The clubs are intended to help ensure that HIV-positive children and adolescents stay in contact with health services, and serve as a conduit for delivery of other services, including health messages and health products. In 2019, Project SOAR conducted a study to describe the Kids Club program and better understand its impact, as detailed in this report. The study’s findings are intended to contribute to the broader evidence base on support groups for young people living with HIV, fill knowledge gaps on how to operationalize and improve this approach, and guide decisions on scale-up and resource allocation in Haiti and globally

Oxygen gradient ektacytometry-derived biomarkers are associated with acute complications in sickle cell disease

We investigated the potential of the point of sickling (PoS; the pO2 tension at which red cells start to sickle), determined by oxygen gradient ektacytometry to serve as a biomarker associated with the incidence of acute sickle cell disease-related complications in 177 children and 50 adults. In the pediatric cohort, for every 10 mmHg increase in PoS reflecting a greater likelihood of sickling, the likelihood of an individual experiencing >1 type of acute complication increased; the adjusted odds ratio (aOR) was 1.65. For every 0.1 increase in minimum elongation index (EImin; reflecting improved red blood cell deformability at hypoxia), the aOR was 0.50. In the adult cohort, for every 10 mmHg increase in PoS, we found an aOR of 3.00, although this was not significant after correcting for multiple testing. There was a trend for an association between higher PoS and greater likelihood of vaso-occlusive episodes (VOEs; children aOR, 1.35; adults aOR, 2.22). In children, only EImin was associated with VOEs (aOR, 0.68). When data of both cohorts were pooled, significant associations with PoS and/or EImin were found for all acute complications, independently and when >1 type of acute complication was assessed. These findings indicate that oxygen gradient ektacytometry generates novel biomarkers and provides a rationale for further development of these biomarkers in the assessment of clinical severity, evaluation of novel therapies, and as surrogate clinical trial end points. These biomarkers may be useful in assessing efficacy of novel therapies like pyruvate kinase activators, voxelotor, and L-glutamine