CD23 is a glycan-binding receptor in some mammalian species

CD23, the low affinity IgE receptor found on B lymphocytes and other cells, contains a C-terminal lectin-like domain that resembles C-type carbohydrate-recognition domains (CRDs) found in many glycan-binding receptors. In most mammalian species, the CD23 residues required to form a sugar-binding site are present, although binding of CD23 to IgE does not involve sugars. Solid-phase binding competition assays, glycoprotein blotting experiments and glycan array analysis employing the lectin-like domains of cow and mouse CD23 demonstrate that they bind to mannose, N-acetylglucosamine, glucose, and fucose and to glycoproteins that bear these sugars in nonreducing terminal positions. Crystal structures of the cow CRD in the presence of α-methyl mannoside and GlcNAcβ1-2Man reveal that a range of oligosaccharide ligands can be accommodated in an open binding site in which most interactions are with a single terminal sugar residue. Although mouse CD23 shows a pattern of monosaccharide and glycoprotein binding similar to cow CD23, the binding is weaker. In contrast, no sugar binding was observed in similar experiments with human CD23. The absence of sugar-binding activity correlates with accumulation of mutations in the CD23 gene in the primate lineage leading to humans, resulting in loss of key sugar-binding residues. These results are consistent with a role for CD23 in many species as a receptor for potentially pathogenic micro-organisms as well as IgE. However, the ability of CD23 to bind several different ligands varies between species, suggesting that it has distinct functions in different organisms

WEBSIM-COMPASS: a new generation scientific instrument simulator for the E-ELT

International audienceWe present a new scientific instrument simulator dedicated to the E-ELT named WEBSIM-COMPASS, and developed in the frame of the COMPASS project. This simulator builds on the previous series of WEBSIM simulators developed during the ESO E-ELT Design Reference Mission and Instrument Phase A studies. The WEBSIM-COMPASS observations simulator consists in a web interface coupled to an IDL code, which allows the user to perform end-to-end simulations of all E-ELT optical/NIR imagers and spectrographs foreseen for the future 39m European Extremely Large Telescope, i.e., MICADO, HARMONI, and MOSAIC. The simulation pipeline produces fake simulations in FITS format that mimic the result of a data reduction pipeline with perfectly extracted/reduced data. We give a functional description of this new simulator, emphasizing the new functionalities and current developments, and present science cases simulated used as test cases

Assessment of the GCT Prototypes Optical System Implementation and Other Key Performances for the Cherenkov Telescope Array

International audienceThe Cherenkov Telescope Array (CTA) project, led by an international collaborationof institutes, aims to create the world's largest next generation observatory for Very HighEnergy (VHE) gamma-ray astronomy. It will be devoted to observations in a wide band ofenergy, from a few tens of GeV to a few hundreds of TeV with Large, Medium and Small-sizedtelescopes.The Small-Size Telescopes (SSTs) are dedicated to the highest energy range above afew TeV and up to 300 TeV. GCT is an imaging atmospheric Cherenkov telescope (IACT)proposed for the subarray of about 70 SSTs to be installed on the Southern site of CTA inChile. The Observatory of Paris and the National Institute for Earth Sciences and Astronomy(INSU/CNRS) have developed the mechanical structure, mirrors (aspherical lightweightaluminium segments) and control system of the GCT. The GCT is based on a Schwarzschild-Couder (S-C) dual-mirror optical design which has the advantages, compared to the currentIACTs, to offer a wide field of view (~ 9°) while decreasing the cost and volume (~ 9 m x 4 mx 6 m for ~ 11 tons) of the telescope structure, as well as the camera. The prototype (pGCT)has been installed at the Meudon's site of the Observatory of Paris and was the first S-Ctelescope and the first CTA prototype to record VHE events on-sky in November 2015.After three years of intensive testing, pGCT has now been commissioned. This paperis a status report on the complete GCT telescope optical system and the performance it canprovide for CTA

SST-GATE: an innovative telescope for very high energy astronomy

The Cherenkov Telescope Array (CTA) is an international collaboration that aims to create the world's largest (ever) Very High Energy gamma-ray telescope array, consisting of more than 100 telescopes covering an area of several square kilometers to observe the electromagnetic showers generated by incoming cosmic gamma-rays with very high energies (from a few tens of GeV up to over 100 TeV). Observing such sources requires - amongst many other things - a large FoV (Field of View). In the framework of CTA, SST-GATE (Small Size Telescope - GAmma-ray Telescope Elements) aims to investigate and to build one of the two first CTA prototypes based on the Schwarzschild-Couder (SC) optical design that delivers a FoV close to 10 degrees in diameter. To achieve the required performance per unit cost, many improvements in mirror manufacturing and in other technologies are required. We present in this paper the current status of our project. After a brief introduction of the very high energy context, we present the opto-mechanical design, discuss the technological tradeoffs and explain the electronics philosophy that will ensure the telescopes cost is minimised without limiting its capabilities. We then describe the software nedeed to operate the telescope and conclude by presenting the expected telescope performance and some management considerations

COMPASS: an efficient, scalable and versatile numerical platform for the development of ELT AO systems

International audienceno abstrac

Operating performance of the gamma-ray Cherenkov telescope: An end-to-end Schwarzschild–Couder telescope prototype for the Cherenkov Telescope Array

The Cherenkov Telescope Array (CTA) consortium aims to build the next-generation ground-based very-high-energy gamma-ray observatory. The array will feature different sizes of telescopes allowing it to cover a wide gamma-ray energy band from about 20 GeV to above 100 TeV. The highest energies, above 5 TeV, will be covered by a large number of Small-Sized Telescopes (SSTs) with a field-of-view of around 9°. The Gamma-ray Cherenkov Telescope (GCT), based on Schwarzschild–Couder dual-mirror optics, is one of the three proposed SST designs. The GCT is described in this contribution and the first images of Cherenkov showers obtained using the telescope and its camera are presented. These were obtained in November 2015 in Meudon, rance

Operating performance of the gamma-ray Cherenkov telescope: An end-to-end Schwarzschild–Couder telescope prototype for the Cherenkov Telescope Array

The Cherenkov Telescope Array (CTA) consortium aims to build the next-generation ground-based very-high-energy gamma-ray observatory. The array will feature different sizes of telescopes allowing it to cover a wide gamma-ray energy band from about 20 GeV to above 100 TeV. The highest energies, above 5 TeV, will be covered by a large number of Small-Sized Telescopes (SSTs) with a field-of-view of around 9°. The Gamma-ray Cherenkov Telescope (GCT), based on Schwarzschild–Couder dual-mirror optics, is one of the three proposed SST designs. The GCT is described in this contribution and the first images of Cherenkov showers obtained using the telescope and its camera are presented. These were obtained in November 2015 in Meudon, France