| 1. |
- Acharya, B. S., et al.
(author)
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Introducing the CTA concept
- 2013
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In: Astroparticle physics. - : Elsevier BV. - 0927-6505 .- 1873-2852. ; 43, s. 3-18
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Journal article (other academic/artistic)abstract
- The Cherenkov Telescope Array (CTA) is a new observatory for very high-energy (VHE) gamma rays. CTA has ambitions science goals, for which it is necessary to achieve full-sky coverage, to improve the sensitivity by about an order of magnitude, to span about four decades of energy, from a few tens of GeV to above 100 TeV with enhanced angular and energy resolutions over existing VHE gamma-ray observatories. An international collaboration has formed with more than 1000 members from 27 countries in Europe, Asia, Africa and North and South America. In 2010 the CTA Consortium completed a Design Study and started a three-year Preparatory Phase which leads to production readiness of CTA in 2014. In this paper we introduce the science goals and the concept of CTA, and provide an overview of the project. (C) 2013 Elsevier B.V. All rights reserved.
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| 2. |
- Actis, M., et al.
(author)
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Design concepts for the Cherenkov Telescope Array CTA : an advanced facility for ground-based high-energy gamma-ray astronomy
- 2011
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In: Experimental astronomy. - : Springer. - 0922-6435 .- 1572-9508. ; 32:3, s. 193-316
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Journal article (peer-reviewed)abstract
- Ground-based gamma-ray astronomy has had a major breakthrough with the impressive results obtained using systems of imaging atmospheric Cherenkov telescopes. Ground-based gamma-ray astronomy has a huge potential in astrophysics, particle physics and cosmology. CTA is an international initiative to build the next generation instrument, with a factor of 5-10 improvement in sensitivity in the 100 GeV-10 TeV range and the extension to energies well below 100 GeV and above 100 TeV. CTA will consist of two arrays (one in the north, one in the south) for full sky coverage and will be operated as open observatory. The design of CTA is based on currently available technology. This document reports on the status and presents the major design concepts of CTA.
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| 3. |
- Ageron, M., et al.
(author)
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ANTARES : The first undersea neutrino telescope
- 2011
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In: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier. - 0168-9002 .- 1872-9576. ; 656:1, s. 11-38
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Journal article (peer-reviewed)abstract
- The ANTARES Neutrino Telescope was completed in May 2008 and is the first operational Neutrino Telescope in the Mediterranean Sea. The main purpose of the detector is to perform neutrino astronomy and the apparatus also offers facilities for marine and Earth sciences. This paper describes the design, the construction and the installation of the telescope in the deep sea, offshore from Toulon in France. An illustration of the detector performance is given. (C) 2011 Elsevier B.V. All rights reserved.
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| 4. |
- Tremblin, P., et al.
(author)
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Site testing for submillimetre astronomy at Dome C, Antarctica
- 2011
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 535:A112
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Journal article (peer-reviewed)abstract
- Aims. Over the past few years a major effort has been put into the exploration of potential sites for the deployment of submillimetre astronomical facilities. Amongst the most important sites are Dome C and Dome A on the Antarctic Plateau, and the Chajnantor area in Chile. In this context, we report on measurements of the sky opacity at 200 mu m over a period of three years at the French-Italian station, Concordia, at Dome C, Antarctica. We also present some solutions to the challenges of operating in the harsh polar environment.Methods. The 200-mu m atmospheric opacity was measured with a tipper. The forward atmospheric model MOLIERE (Microwave Observation LIne Estimation and REtrieval) was used to calculate the atmospheric transmission and to evaluate the precipitable water vapour content (PWV) from the observed sky opacity. These results have been compared with satellite measurements from the Infrared Atmospheric Sounding Interferometer (IASI) on Metop-A, with balloon humidity sondes and with results obtained by a ground-based microwave radiometer (HAMSTRAD). In addition, a series of experiments has been designed to study frost formation on surfaces, and the temporal and spatial evolution of thermal gradients in the low atmosphere.Results. Dome C offers exceptional conditions in terms of absolute atmospheric transmission and stability for submillimetre astronomy. Over the austral winter the PWV exhibits long periods during which it is stable and at a very low level (0.1 to 0.3 mm). Higher values (0.2 to 0.8 mm) of PWV are observed during the short summer period. Based on observations over three years, a transmission of around 50% at 350 mu m is achieved for 75% of the time. The 200-mu m window opens with a typical transmission of 10% to 15% for 25% of the time.Conclusions. Dome C is one of the best accessible sites on Earth for submillimetre astronomy. Observations at 350 or 450 mu m are possible all year round, and the 200-mu m window opens long enough and with a sufficient transparency to be useful. Although the polar environment severely constrains hardware design, a permanent observatory with appropriate technical capabilities is feasible. Because of the very good astronomical conditions, high angular resolution and time series (multi-year) observations at Dome C with a medium size single dish telescope would enable unique studies to be conducted, some of which are not otherwise feasible even from space.
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| 5. |
- Malbet, F., et al.
(author)
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High precision astrometry mission for the detection and characterization of nearby habitable planetary systems with the Nearby Earth Astrometric Telescope (NEAT)
- 2012
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In: Experimental Astronomy. - : Springer Science and Business Media LLC. - 0922-6435 .- 1572-9508. ; 34:2, s. 385-413
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Journal article (peer-reviewed)abstract
- A complete census of planetary systems around a volume-limited sample of solar-type stars (FGK dwarfs) in the Solar neighborhood (d a parts per thousand currency signaEuro parts per thousand 15 pc) with uniform sensitivity down to Earth-mass planets within their Habitable Zones out to several AUs would be a major milestone in extrasolar planets astrophysics. This fundamental goal can be achieved with a mission concept such as NEAT-the Nearby Earth Astrometric Telescope. NEAT is designed to carry out space-borne extremely-high-precision astrometric measurements at the 0.05 mu as (1 sigma) accuracy level, sufficient to detect dynamical effects due to orbiting planets of mass even lower than Earth's around the nearest stars. Such a survey mission would provide the actual planetary masses and the full orbital geometry for all the components of the detected planetary systems down to the Earth-mass limit. The NEAT performance limits can be achieved by carrying out differential astrometry between the targets and a set of suitable reference stars in the field. The NEAT instrument design consists of an off-axis parabola single-mirror telescope (D = 1 m), a detector with a large field of view located 40 m away from the telescope and made of 8 small movable CCDs located around a fixed central CCD, and an interferometric calibration system monitoring dynamical Young's fringes originating from metrology fibers located at the primary mirror. The mission profile is driven by the fact that the two main modules of the payload, the telescope and the focal plane, must be located 40 m away leading to the choice of a formation flying option as the reference mission, and of a deployable boom option as an alternative choice. The proposed mission architecture relies on the use of two satellites, of about 700 kg each, operating at L2 for 5 years, flying in formation and offering a capability of more than 20,000 reconfigurations. The two satellites will be launched in a stacked configuration using a Soyuz ST launch vehicle. The NEAT primary science program will encompass an astrometric survey of our 200 closest F-, G- and K-type stellar neighbors, with an average of 50 visits each distributed over the nominal mission duration. The main survey operation will use approximately 70% of the mission lifetime. The remaining 30% of NEAT observing time might be allocated, for example, to improve the characterization of the architecture of selected planetary systems around nearby targets of specific interest (low-mass stars, young stars, etc.) discovered by Gaia, ground-based high-precision radial-velocity surveys, and other programs. With its exquisite, surgical astrometric precision, NEAT holds the promise to provide the first thorough census for Earth-mass planets around stars in the immediate vicinity of our Sun.
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| 6. |
- Schneider, N., et al.
(author)
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Atmospheric transmission at Dome C between 0 and 10 THz
- 2010
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In: EAS Publications Series. - : EDP Sciences. - 1633-4760 .- 1638-1963. ; 40, s. 327-332
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Journal article (peer-reviewed)abstract
- We present model calculations of the atmospheric transmission for DOME C in Antarctica for frequencies up to 10THz (30 μm) using the forward model MOLIERE-5. Measurements of precipitable water vapor (pwv), obtained by the SUMMIT radiometer installed at the Concordia station during 2008 and working at a wavelength of 200μm, are translated into atmospheric transmission using MOLIERE. Quartiles of transmission, calculated from 200μm data are extrapolated to 350 μm and compared to the CCAT (Cornell-Caltech Atacama Telescope) site in Chile. It turns out that for 25% of the time at DOME C (CCAT), the transmission is around 20% (5%) at 200μm. This corresponds to a pwv of 0.18mm for DOME C. At 350μm, for 50% of time at DOME C (CCAT) the transmission is around 55% (25%). This corresponds to a pwv of 0.22mm for DOME C. These results show that DOME C is one of the best observing sites on Earth for submm-astronomy with respect to high atmospheric transmission over long time periods
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| 7. |
- Tremblin, P., et al.
(author)
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Dome C: The best accessible site on Earth for submillimetre astronomy
- 2010
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In: EAS Publications Series. - : EDP Sciences. - 1633-4760 .- 1638-1963. ; 40, s. 333-336
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Journal article (peer-reviewed)abstract
- We present preliminary results of the measurements of sky transparency conducted at Dome C during the winter 2008. Using MOLIERE modeling, we estimate a low precipitable water vapour content above Concordia station, which is very promising for future submillimetre wave observations on the Antarctic Plateau.
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| 8. |
- Durand, Y., et al.
(author)
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EUROSERVER: Energy efficient node for European micro-servers
- 2014
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In: 17th Euromicro Conference on Digital System Design, DSD 2014; Verona; Italy; 27 August 2014 through 29 August 2014. ; , s. 206-213
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Conference paper (peer-reviewed)abstract
- EUROSERVER is a collaborative project that aims to dramatically improve data centre energy-efficiency, cost, and software efficiency. It is addressing these important challenges through the coordinated application of several key recent innovations: 64-bit ARM cores, 3D heterogeneous silicon-on-silicon integration, and fully-depleted silicon-on-insulator (FD SOI) process technology, together with new software techniques for efficient resource management, including resource sharing and workload isolation. We are pioneering a system architecture approach that allows specialized silicon devices to be built even for low-volume markets where NRE costs are currently prohibitive. The EUROSERVER device will embed multiple silicon 'chiplets' on an active silicon interposer. Its system architecture is being driven by requirements from three use cases: data centres and cloud computing, telecom infrastructures, and high-end embedded systems. We will build two fully integrated full-system prototypes, based on a common micro-server board, and targeting embedded servers and enterprise servers.
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| 9. |
- Gagliardini, O., et al.
(author)
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Capabilities and performance of Elmer/Ice, a new-generation ice sheet model
- 2013
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In: Geoscientific Model Development. - : Copernicus GmbH. - 1991-959X .- 1991-9603. ; 6:4, s. 1299-1318
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Journal article (peer-reviewed)abstract
- The Fourth IPCC Assessment Report concluded that ice sheet flow models, in their current state, were unable to provide accurate forecast for the increase of polar ice sheet discharge and the associated contribution to sea level rise. Since then, the glaciological community has undertaken a huge effort to develop and improve a new generation of ice flow models, and as a result a significant number of new ice sheet models have emerged. Among them is the parallel finite-element model Elmer/Ice, based on the open-source multi-physics code Elmer. It was one of the first full-Stokes models used to make projections for the evolution of the whole Greenland ice sheet for the coming two centuries. Originally developed to solve local ice flow problems of high mechanical and physical complexity, Elmer/Ice has today reached the maturity to solve larger-scale problems, earning the status of an ice sheet model. Here, we summarise almost 10 yr of development performed by different groups. Elmer/Ice solves the full-Stokes equations, for isotropic but also anisotropic ice rheology, resolves the grounding line dynamics as a contact problem, and contains various basal friction laws. Derived fields, like the age of the ice, the strain rate or stress, can also be computed. Elmer/Ice includes two recently proposed inverse methods to infer badly known parameters. Elmer is a highly parallelised code thanks to recent developments and the implementation of a block preconditioned solver for the Stokes system. In this paper, all these components are presented in detail, as well as the numerical performance of the Stokes solver and developments planned for the future.
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| 10. |
- Hogan, C. J., et al.
(author)
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Fission yeast Iec1-Ino80-mediated nucleosome eviction regulates nucleotide and phosphate metabolism
- 2010
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In: Molecular and Cellular Biology. - 0270-7306 .- 1098-5549. ; 30:3, s. 657-674
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Journal article (peer-reviewed)abstract
- Ino80 is an ATP-dependent nucleosome-remodeling enzyme involved in transcription, replication, and the DNA damage response. Here, we characterize the fission yeast Ino80 and find that it is essential for cell viability. We show that the Ino80 complex from fission yeast mediates ATP-dependent nucleosome remodeling in vitro. The purification of the Ino80-associated complex identified a highly conserved complex and the presence of a novel zinc finger protein with similarities to the mammalian transcriptional regulator Yin Yang 1 (YY1) and other members of the GLI-Krüppel family of proteins. Deletion of this Iec1 protein or the Ino80 complex subunit arp8, ies6, or ies2 causes defects in DNA damage repair, the response to replication stress, and nucleotide metabolism. We show that Iec1 is important for the correct expression of genes involved in nucleotide metabolism, including the ribonucleotide reductase subunit cdc22 and phosphate- and adenineresponsive genes. We find that Ino80 is recruited to a large number of promoter regions on phosphate starvation, including those of phosphate- and adenine-responsive genes that depend on Iec1 for correct expression. Iec1 is required for the binding of Ino80 to target genes and subsequent histone loss at the promoter and throughout the body of these genes on phosphate starvation. This suggests that the Iec1-Ino80 complex promotes transcription through nucleosome eviction.
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| 11. |
- Leblond, Claire S, et al.
(author)
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Meta-analysis of SHANK Mutations in Autism Spectrum Disorders: A Gradient of Severity in Cognitive Impairments.
- 2014
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In: PLoS genetics. - : Public Library of Science (PLoS). - 1553-7404. ; 10:9
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Journal article (peer-reviewed)abstract
- SHANK genes code for scaffold proteins located at the post-synaptic density of glutamatergic synapses. In neurons, SHANK2 and SHANK3 have a positive effect on the induction and maturation of dendritic spines, whereas SHANK1 induces the enlargement of spine heads. Mutations in SHANK genes have been associated with autism spectrum disorders (ASD), but their prevalence and clinical relevance remain to be determined. Here, we performed a new screen and a meta-analysis of SHANK copy-number and coding-sequence variants in ASD. Copy-number variants were analyzed in 5,657 patients and 19,163 controls, coding-sequence variants were ascertained in 760 to 2,147 patients and 492 to 1,090 controls (depending on the gene), and, individuals carrying de novo or truncating SHANK mutations underwent an extensive clinical investigation. Copy-number variants and truncating mutations in SHANK genes were present in ∼1% of patients with ASD: mutations in SHANK1 were rare (0.04%) and present in males with normal IQ and autism; mutations in SHANK2 were present in 0.17% of patients with ASD and mild intellectual disability; mutations in SHANK3 were present in 0.69% of patients with ASD and up to 2.12% of the cases with moderate to profound intellectual disability. In summary, mutations of the SHANK genes were detected in the whole spectrum of autism with a gradient of severity in cognitive impairment. Given the rare frequency of SHANK1 and SHANK2 deleterious mutations, the clinical relevance of these genes remains to be ascertained. In contrast, the frequency and the penetrance of SHANK3 mutations in individuals with ASD and intellectual disability-more than 1 in 50-warrant its consideration for mutation screening in clinical practice.
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| 18. |
- Tremblin, P., et al.
(author)
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A worldwide comparison of the best sites for submillimetre astronomy
- 2012
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In: Proceedings of the International Astronomical Union. - 1743-9213 .- 1743-9221. - 9781107033771 ; 8:S288, s. 29-33
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Conference paper (peer-reviewed)abstract
- Over the past few years a major effort has been put into the exploration of potential sites for the deployment of submillimetre (submm) astronomical facilities. Amongst the most important sites are Dome C and Dome A on the Antarctic Plateau, and the Chajnantor area in Chile. In this context, we report on measurements of the sky opacity at 200 μm over a period of three years at the French-Italian station, Concordia, at Dome C, Antarctica. Based on satellite data, we present a comparison of the atmospheric transmission at 200, 350 μm between the best potential/known sites for submillimetre astronomy all around the world. The precipitable water vapour (PWV) was extracted from satellite measurements of the Infrared Atmospheric Sounding Interferometer (IASI) on the METOP-A satellite, between 2008 and 2010. We computed the atmospheric transmission at 200 μm and 350 μm using the forward atmospheric model MOLIERE (Microwave Observation LIne Estimation and REtrieval). This method allows us to compare known sites all around the world without the calibration biases of multiple in-situ instruments, and to explore the potential of new sites.
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| 19. |
- Tremblin, P., et al.
(author)
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Worldwide site comparison for submillimetre astronomy
- 2012
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 548, s. A65-
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Journal article (peer-reviewed)abstract
- Aims. The most important limitation for ground-based submillimetre (submm) astronomy is the broad-band absorption of the total water vapour in the atmosphere above an observation site, often expressed as the precipitable water vapour (PWV). A long-term statistic on the PWV is thus mandatory to characterize the quality of an existing or potential site for observational submm-astronomy. In this study we present a three-year statistic (2008–2010) of the PWV for ground-based telescope sites all around the world and for stratospheric altitudes relevant for SOFIA (Stratospheric Observatory for Far-Infrared Astronomy). The submm-transmission is calculated for typical PWVs using an atmospheric model.Methods. We used data from IASI (Infrared Atmospheric Sounding Interferometer) on the Metop-A satellite to retrieve water vapour profiles for each site (11 in total, comprising Antarctica, Chile, Mauna Kea, Greenland, Tibet). The use of a single instrument to make the comparison provides unbiased data with a common calibration method. The profiles are integrated above the mountain/stratospheric altitude to get an estimation of the PWV. We then applied the atmospheric model MOLIERE (Microwave Observation and LIne Estimation and REtrieval) to compute the corresponding atmospheric absorption for wavelengths between 150 μm and 3 mm.Results. We present the absolute PWV values for each site sorted by year and time percentage. The PWV corresponding to the first decile (10%) and the quartiles (25%, 50%, 75%) are calculated and transmission curves between 150 μm and 3 mm for these values are shown. The Antarctic and South-American sites present very good conditions for submillimetre astronomy. The 350 μm and 450 μm atmospheric windows are open all year long, whereas the 200 μm atmospheric window opens reasonably for 25% of the time in Antarctica and the extremely high-altitude sites in Chile. Potential interesting new facilities are Macon in Argentina and Summit in Greenland, which show similar conditions to for example, Mauna Kea (Hawaii). For SOFIA, we present transmission curves for different altitudes (11 to 14 km), PWV values, and higher frequencies (up to 5 THz) in more detail. Though the atmosphere at these altitude is generally very transparent, the absorption at very high frequencies becomes more important, partly caused by minor species. The method presented in this paper could identify sites on Earth, with great potential for submillimetre astronomy, and guide future site testing campaigns in situ.
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