First whole atmosphere night-time seeing measurements at Dome C, Antarctica

We report site testing results obtained in night-time during the polar autumn and winter at Dome C. These results were collected during the first Concordia winterover by A. Agabi. They are based upon seeing and isoplanatic angle monitoring, as well as in-situ balloon measurements 2 of the refractive index structure constant profiles Cn (h). Atmosphere is divided into two regions: (i) a 36 m high surface layer responsible of 87% of the turbulence and (ii) a very stable free atmosphere above with a median seeing of 0.36+-0.19 arcsec at an elevation of h = 30 m. The median seeing measured with a DIMM placed on top of a 8.5 m high tower is 1.3+-0.8 arcsec.Comment: accepted for publication in PASP (oct 2005

Site testing in summer at Dome C, Antarctica

We present summer site testing results based on DIMM data obtained at Dome C, Antarctica. These data have been collected on the bright star Canopus during two 3-months summer campaigns in 2003-2004 and 2004-2005. We performed continuous monitoring of the seeing a nd the isoplanatic angle in the visible. We found a median seeing of 0.54 \arcsec and a median isoplanatic angle of 6.8 \arcsec. The seeing appears to have a deep minimum around 0.4 \arcsec almost every day in late afternoon

Near-Infrared interferometry of Eta Carinae with high spatial and spectral resolution using the VLTI and the AMBER instrument

We present the first NIR spectro-interferometry of the LBV Eta Carinae. The K band observations were performed with the AMBER instrument of the ESO Very Large Telescope Interferometer using three 8.2m Unit Telescopes with baselines from 42 to 89m. The aim of this work is to study the wavelength dependence of Eta Car's optically thick wind region with a high spatial resolution of 5 mas (11 AU) and high spectral resolution. The medium spectral resolution observations (R=1,500) were performed in the wavelength range around both the HeI 2.059 micron and the Br gamma 2.166 micron emission lines, the high spectral resolution observations (R=12,000) only in the Br gamma line region. In the K-band continuum, a diameter of 4.0 +/-0.2 mas (Gaussian FWHM, fit range 28-89m) was measured for Eta Car's optically thick wind region. If we fit Hillier et al. (2001) model visibilities to the observed AMBER visibilities, we obtain 50 % encircled-energy diameters of 4.2, 6.5 and 9.6mas in the 2.17 micron continuum, the HeI, and the Br gamma emission lines, respectively. In the continuum near the Br gamma line, an elongation along a position angle of 120+/-15 degrees was found, consistent with previous VLTI/VINCI measurements by van Boekel et al. (2003). We compare the measured visibilities with predictions of the radiative transfer model of Hillier et al. (2001), finding good agreement. Furthermore, we discuss the detectability of the hypothetical hot binary companion. For the interpretation of the non-zero differential and closure phases measured within the Br gamma line, we present a simple geometric model of an inclined, latitude-dependent wind zone. Our observations support theoretical models of anisotropic winds from fast-rotating, luminous hot stars with enhanced high-velocity mass loss near the polar regions.Comment: 22 pages, 14 figures, 2 tables; A&A in pres

Spectroscopic Signatures of Convection in the Spectrum of Procyon. Fundamental Parameters and Iron Abundance

We have observed the spectrum of Procyon A (F5IV) from 4559 to 5780 A with a S/N of ~ 1e3 and a resolving power of 2e5. We have measured the line bisectors and relative line shifts of a large number of Fe I and Fe II lines, comparing them to those found in the Sun. A three-dimensional(3D) hydrodynamical model atmosphere has been computed and is tested against observations. The model reproduces in detail most of the features observed, although we identify some room for improvement. At all levels, the comparison of the 3D time-dependent calculations with the observed spectral lines shows a much better agreement than for classical homogeneous models, making it possible to refine previous estimates of the iron abundance, the projected rotational velocity, the limb-darkening, and the systemic velocity of the Procyon binary system. The difference between the iron abundance determined with the 3D model and its 1D counterpart is <~ 0.05 dex. We find consistency between the iron abundance derived from Fe I and Fe II lines, suggesting that departures from LTE in the formation of the studied lines are relatively small. The scatter in the iron abundance determined from different lines still exceeds the expectations from the uncertainties in the atomic data, pointing out that one or more components in the modeling can be refined further.Comment: 30 pages, 19 figures; uses emulateapj.sty (included); to appear in ApJ (Feb 2002

The wide-field, multiplexed, spectroscopic facility WEAVE: Survey design, overview, and simulated implementation

WEAVE, the new wide-field, massively multiplexed spectroscopic survey facility for the William Herschel Telescope, will see first light in late 2022. WEAVE comprises a new 2-degree field-of-view prime-focus corrector system, a nearly 1000-multiplex fibre positioner, 20 individually deployable 'mini' integral field units (IFUs), and a single large IFU. These fibre systems feed a dual-beam spectrograph covering the wavelength range 366$-$959\,nm at $R\sim5000$, or two shorter ranges at $R\sim20\,000$. After summarising the design and implementation of WEAVE and its data systems, we present the organisation, science drivers and design of a five- to seven-year programme of eight individual surveys to: (i) study our Galaxy's origins by completing Gaia's phase-space information, providing metallicities to its limiting magnitude for $\sim$3 million stars and detailed abundances for $\sim1.5$ million brighter field and open-cluster stars; (ii) survey $\sim0.4$ million Galactic-plane OBA stars, young stellar objects and nearby gas to understand the evolution of young stars and their environments; (iii) perform an extensive spectral survey of white dwarfs; (iv) survey $\sim400$ neutral-hydrogen-selected galaxies with the IFUs; (v) study properties and kinematics of stellar populations and ionised gas in $z<0.5$ cluster galaxies; (vi) survey stellar populations and kinematics in $\sim25\,000$ field galaxies at $0.3\lesssim z \lesssim 0.7$; (vii) study the cosmic evolution of accretion and star formation using $>1$ million spectra of LOFAR-selected radio sources; (viii) trace structures using intergalactic/circumgalactic gas at $z>2$. Finally, we describe the WEAVE Operational Rehearsals using the WEAVE Simulator.Comment: 41 pages, 27 figures, accepted for publication by MNRA

The wide-field, multiplexed, spectroscopic facility WEAVE: Survey design, overview, and simulated implementation

WEAVE, the new wide-field, massively multiplexed spectroscopic survey facility for the William Herschel Telescope, will see first light in late 2022. WEAVE comprises a new 2-degree field-of-view prime-focus corrector system, a nearly 1000-multiplex fibre positioner, 20 individually deployable 'mini' integral field units (IFUs), and a single large IFU. These fibre systems feed a dual-beam spectrograph covering the wavelength range 366−959\,nm at R∼5000, or two shorter ranges at R∼20000. After summarising the design and implementation of WEAVE and its data systems, we present the organisation, science drivers and design of a five- to seven-year programme of eight individual surveys to: (i) study our Galaxy's origins by completing Gaia's phase-space information, providing metallicities to its limiting magnitude for ∼3 million stars and detailed abundances for ∼1.5 million brighter field and open-cluster stars; (ii) survey ∼0.4 million Galactic-plane OBA stars, young stellar objects and nearby gas to understand the evolution of young stars and their environments; (iii) perform an extensive spectral survey of white dwarfs; (iv) survey ∼400 neutral-hydrogen-selected galaxies with the IFUs; (v) study properties and kinematics of stellar populations and ionised gas in z1 million spectra of LOFAR-selected radio sources; (viii) trace structures using intergalactic/circumgalactic gas at z>2. Finally, we describe the WEAVE Operational Rehearsals using the WEAVE Simulator

Étude de la thermodynamique et de la coopérativité du repliement des protéines par haute pression

This thesis work focuses on the study of protein though the use of high pressure. There are three main points subject that are being inquired here. The first is the study of cooperativity and folding landscape of a repeat protein (Anp32a) though the use high pressure denaturation at different temperatures. The second concerns the investigation of the determinant of thermal expansivity in the folded state of protein using high pressure NMR, and the well characterized Staphylococcal Nuclease (SNase) and some of its mutants. Finally, a last article on the pressure stability of the model mini protein Tryptophan cage variant Tc5b by a combination of high pressure NMR and full atomic replica exchange simulations.Ce travail de thèse ce concentre sur l’étude des protéines par l’usage de haute pression. Les articles présentés ici sont précéder d’une introduction présentant les différents modèles physiques utilisés pour décrire le repliement des protéines, une introduction posant les bases de la thermodynamique, ainsi que l’origine de la stabilité thermodynamique des protéines dans leur état plies. Il y a trois sujets principaux aborder dans ce mémoire. Le premier est l’étude de la coopérativité du repliement et du paysage de repliement de la protéine à répétition PP32 (Anp32a) a travers l’utilisation de la pression a différentes températures. La seconde étude concerne l’investigation de l’origine de l’expansivité thermique des protéines pliées grâce à l’utilisation de RMN haute pression et de la protéine très bien caractérisée Staphylococcal Nuclease (SNase) et de certaine de ses mutantes. Finalement, un dernier article sur la stabilité sous pression de la variant TC5b de la mini protéine model tryptophan-cage grâce une combinaison de RMN et de simulations moléculaires tout-atomes en « replica exchange »

Study of the thermodynamics and cooperativity of protein folding by high pressure

Ce travail de thèse ce concentre sur l’étude des protéines par l’usage de haute pression. Les articles présentés ici sont précéder d’une introduction présentant les différents modèles physiques utilisés pour décrire le repliement des protéines, une introduction posant les bases de la thermodynamique, ainsi que l’origine de la stabilité thermodynamique des protéines dans leur état plies. Il y a trois sujets principaux aborder dans ce mémoire. Le premier est l’étude de la coopérativité du repliement et du paysage de repliement de la protéine à répétition PP32 (Anp32a) a travers l’utilisation de la pression a différentes températures. La seconde étude concerne l’investigation de l’origine de l’expansivité thermique des protéines pliées grâce à l’utilisation de RMN haute pression et de la protéine très bien caractérisée Staphylococcal Nuclease (SNase) et de certaine de ses mutantes. Finalement, un dernier article sur la stabilité sous pression de la variant TC5b de la mini protéine model tryptophan-cage grâce une combinaison de RMN et de simulations moléculaires tout-atomes en « replica exchange ».This thesis work focuses on the study of protein though the use of high pressure. There are three main points subject that are being inquired here. The first is the study of cooperativity and folding landscape of a repeat protein (Anp32a) though the use high pressure denaturation at different temperatures. The second concerns the investigation of the determinant of thermal expansivity in the folded state of protein using high pressure NMR, and the well characterized Staphylococcal Nuclease (SNase) and some of its mutants. Finally, a last article on the pressure stability of the model mini protein Tryptophan cage variant Tc5b by a combination of high pressure NMR and full atomic replica exchange simulations