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International audience; Introduction et but de l’étudeL'objectif de cette étude est d'évaluer la capacité d’un mélange protéique végétal à maintenir la masse maigre, la masse musculaire et sa fonctionnalité chez des rats âgés, par comparaison à la référence des protéines de lait, dans le cadre d'un régime prudent ou occidental.Matériel et MéthodesLe mélange protéique végétal qui a été ici étudié chez le rat a été conçu spécifiquement pour la personne âgée à risque sarcopénique et cardiométabolique, par optimisation de sa composition en ingrédients protéiques sources. Les critères d’optimisation portaient sur l'équilibre en acides aminés indispensables et les teneurs en leucine, arginine et cystéine, pour favoriser théoriquement l’augmentation de la synthèse protéique musculaire et la réduction du stress oxydant de façon synergique. Le mélange protéique optimisé contient des isolats protéiques de lupin, pomme de terre, riz, zéine et albumine de colza. Des rats Wistar mâles âgés, modèle animal de sarcopénie, ont été répartis aléatoirement en quatre groupes de régimes différents selon la source des protéines – laitière (PA) ou végétale (PV) – et la teneur énergétique (standard, avec amidon, ou élevée, avec graisses saturées et saccharose), pendant 4 mois (n = 96, 18 - 22 mois). La glycémie et l'insulinémie ainsi que la composition corporelle (par écho IRM) ont été mesurées tous les deux mois. La fonctionnalité musculaire (selon le système Catwalk XT) a été évaluée avant et après le régime expérimental. Enfin, après 4 mois de régime, les vitesses de synthèse protéique dans le muscle gastrocnémien ont été mesurées par la technique de la surcharge en 13C-valine.Résultats et Analyses statistiquesSur l'ensemble de la période, l'ingéré protéique moyen était similaire dans tous les groupes. Le poids des animaux a augmenté dans tous les groupes au cours de l'expérience (P = 0,001) ; la nature des protéines toutes choses égales par ailleurs n’a pas affecté cette prise de poids. Le régime riche en graisse et en saccharose a augmenté la graisse corporelle (et donc le poids), mais a eu peu d'impact sur la sensibilité à l'insuline et les métabolismes connexes, ne permettant donc pas d’évaluer comme prévu les effets du mélange protéique végétal dans des situations de résistance à l'insuline. En revanche, à la fin de l'expérience, l'insulinémie à jeun était significativement plus faible chez les rats PV que chez les rats PA (P < 0.05).Il n'y a pas de différences significatives de masse maigre ou de masse musculaireentre les groupes quelle que soit la nature des protéines.Globalement, la prise alimentaire a provoqué une augmentation de la vitesse de synthèse protéique (ASR, g/h) dans le muscle gastrocnémien (+13% par rapport àl’état postabsorptif). La nature des protéines et le niveau d’énergie n’ont pas affecté les ASR et leur variation postprandiale. En ajoutant la masse musculaire en covariable, un taux de synthèse protéique (FSR, %/h) plus élevé est mis en évidence chez les rats PV (7,6 ± 0,2 %/h vs 6,5 ± 0,2 %/h pour les rats PA). La masse musculaire n'ayant pas été différemment affectée par la nature des protéines, ces résultats suggèrent une augmentation dans les mêmes proportions de la protéolyse musculaire, et donc un taux de renouvellement plus élevé avec le mélange PV. À notre connaissance, un tel résultat n'a pas été rapporté dans lalittérature.Les résultats de l’analyse de la locomotion des animaux ne permettent pas de conclure à un effet direct du vieillissement ou de la source des protéines avec deseffets divergents des protéines végétales sur la durée de la course et la vitesse moyenne par exemple.ConclusionDans ce modèle de rat âgé, sur le long terme, nous avons montré qu'un mélangeapproprié de protéines végétales peut remplacer de manière satisfaisante les protéines du lait. En effet, il n'entraîne aucune différence sur la réponse de la synthèse des protéines musculaires à l'alimentation ; et sur l'évolution de la masse maigre et de la masse musculaire au cours du vieillissement. Ces résultats offrent une preuve de concept innovante d'un point de vue nutritionnel : des mélanges de protéines végétales bien conçus peuvent avoir une valeur nutritionnelle élevée même dans des situations exigeantes telles que le métabolisme protéique vieillissant.

Context. The inner few au region of planet-forming disks is a complex environment. High angular resolution observations have a key role in understanding the disk structure and the dynamical processes at work. Aims. In this study we aim to characterize the mid-infrared brightness distribution of the inner disk of the young intermediate-mass star HD 163296, from VLTI/MATISSE observations. Methods. We use geometric models to fit the data. Our models include a smoothed ring, a flat disk with inner cavity, and a 2D Gaussian. The models can account for disk inclination and for azimuthal asymmetries as well. We also perform numerical hydro-dynamical simulations of the inner edge of the disk. Results. Our modeling reveals a significant brightness asymmetry in the L-band disk emission. The brightness maximum of the asymmetry is located at the NW part of the disk image, nearly at the position angle of the semimajor axis. The surface brightness ratio in the azimuthal variation is $3.5 \pm 0.2$. Comparing our result on the location of the asymmetry with other interferometric measurements, we confirm that the morphology of the $r, accepted for publication in A&A

The nature of circumstellar envelopes (CSE) around Cepheids is still a matter of debate. The physical origin of their infrared (IR) excess could be either a shell of ionized gas, or a dust envelope, or both. This study aims at constraining the geometry and the IR excess of the environment of the long-period Cepheid $\ell$ Car (P=35.5 days) at mid-IR wavelengths to understand its physical nature. We first use photometric observations in various bands and Spitzer Space Telescope spectroscopy to constrain the IR excess of $\ell$ Car. Then, we analyze the VLTI/MATISSE measurements at a specific phase of observation, in order to determine the flux contribution, the size and shape of the environment of the star in the L band. We finally test the hypothesis of a shell of ionized gas in order to model the IR excess. We report the first detection in the L band of a centro-symmetric extended emission around l Car, of about 1.7$R_\star$ in FWHM, producing an excess of about 7.0\% in this band. In the N band, there is no clear evidence for dust emission from VLTI/MATISSE correlated flux and Spitzer data. On the other side, the modeled shell of ionized gas implies a more compact CSE ($1.13\pm0.02\,R_\star$) and fainter (IR excess of 1\% in the L band). We provide new evidences for a compact CSE of $\ell$ Car and we demonstrate the capabilities of VLTI/MATISSE for determining common properties of CSEs. While the compact CSE of $\ell$ Car is probably of gaseous nature, the tested model of a shell of ionized gas is not able to simultaneously reproduce the IR excess and the interferometric observations. Further Galactic Cepheids observations with VLTI/MATISSE are necessary for determining the properties of CSEs, which may also depend on both the pulsation period and the evolutionary state of the stars., Comment: 13 pages, 8 figures, accepted in Astronomy and Astrophysics

Context. Protoplanetary disks show large diversity regarding their morphology and dust composition. With mid-infrared interferometry the thermal emission of disks can be spatially resolved, and the distribution and properties of the dust within can be studied. Aims. Our aim is to perform a statistical analysis on a large sample of 82 disks around low- and intermediate-mass young stars, based on mid-infrared interferometric observations. We intend to study the distribution of disk sizes, variability, and the silicate dust mineralogy. Methods. Archival mid-infrared interferometric data from the MIDI instrument on the VLTI are homogeneously reduced and calibrated. Geometric disk models are used to fit the observations to get spatial information about the disks. An automatic spectral decomposition pipeline is applied to analyze the shape of the silicate feature. Results. We present the resulting data products in the form of an atlas, containing N band correlated and total spectra, visibilities, and differential phases. The majority of our data can be well fitted with a continuous disk model, except for a few objects, where a gapped model gives a better match. From the mid-infrared size--luminosity relation we find that disks around T Tauri stars are generally colder and more extended with respect to the stellar luminosity than disks around Herbig Ae stars. We find that in the innermost part of the disks ($r \lesssim 1$~au) the silicate feature is generally weaker than in the outer parts, suggesting that in the inner parts the dust is substantially more processed. We analyze stellar multiplicity and find that in two systems (AB Aur and HD 72106) data suggest a new companion or asymmetric inner disk structure. We make predictions for the observability of our objects with the upcoming MATISSE instrument, supporting the practical preparations of future MATISSE observations of T Tauri stars., Comment: 54 pages, 14 figures, 6 tables, accepted for publication in A&A

Context. DG Tau is a low-mass pre-main sequence star, whose strongly accreting protoplanetary disk exhibits a so-far enigmatic behavior: its mid-infrared thermal emission is strongly time-variable, even turning the 10 $��$m silicate feature from emission to absorption temporarily. Aims. We look for the reason for the spectral variability at high spatial resolution and at multiple epochs. Methods. We study the temporal variability of the mid-infrared interferometric signal, observed with the VLTI/MIDI instrument at six epochs between 2011 and 2014. We fit a geometric disk model to the observed interferometric signal to obtain spatial information about the disk. We also model the mid-infrared spectra by template fitting to characterize the profile and time dependence of the silicate emission. We use physically motivated radiative transfer modeling to interpret the mid-infrared interferometric spectra. Results. The inner disk (r1-3 au) spectra show a crystalline silicate feature in emission, similar to the spectra of comet Hale-Bopp. The striking difference between the inner and outer disk spectral feature is highly unusual among T Tauri stars. The mid-infrared variability is dominated by the outer disk. The strength of the silicate feature changed by more than a factor of two. Between 2011 and 2014 the half-light radius of the mid-infrared-emitting region decreased from 1.15 to 0.7 au. Conclusions. For the origin of the absorption we discuss four possible explanations: a cold obscuring envelope, an accretion heated inner disk, a temperature inversion on the disk surface and a misaligned inner geometry. The silicate emission in the outer disk can be explained by dusty material high above the disk plane, whose mass can change with time, possibly due to turbulence in the disk., 16 pages, 13 figures

The signatures of dust processing and grain growth – related to the formation of rocky planets – are easily seen in midinfrared spectral features. One important diagnostic tool in this context is the silicate feature in the spectra of young stellar objects (YSO). The low-mass YSO, DG Tau shows unique temporal variations in its silicate feature. We conducted multi-epoch observations of DG Tau with the MID-Infrared Interferometric instrument of the Very Large Telescope Interferometer to obtain the spectra of the inner and outer disk regions in order to investigate where the previously reported variations of the silicate feature originate from. Here we present the preliminary results of the first two epochs of observations. We found that on a time-scale of two months, the source showed significant brightening. At the same time the mid-infrared emitting region expanded. While the identification of the silicate feature is difficult, our results qualitatively agree with the scenario explaining the varying silicate feature with dust lifted up above the disk. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We briefly introduce radio interferometry and review the image reconstruction methods developed for radio interferometers in the past half a century. We also summarise the similarities and the main differences between radio and optical/infrared interferometry.

We describe a mathematical formalism for the teaching optical interferometer concept developed by P. Lawson. In this experiment, the co-addition of several interferometric fringe patterns obtained for different baselines between individual telescopes is the image of the source, for the simple reason that the fringe patterns build up the image of the observed source through a convolution product. This basic principle is of interest since it allows one to tackle the image reconstruction for optical long-baseline interferometry through an approach which is complementary to the use of the Fourier plane. Thus, image reconstruction can be thought of in the fringe plane. It allows a better understanding of the fundamental limits of the image dynamical range.

In February 1997, the Japanese radio astronomy satellite HALCA was launched to provide the space-bourne element for the VLBI Space Observatory Programme (VSOP) mission. Approximately twenty-five percent of the mission time was dedicated to the VSOP Survey of bright compact Active Galactic Nuclei (AGN) at 5 GHz. This paper, the fifth in the series, presents images and models for the remaining 140 sources not included in Paper III, which contained 102 sources. For most sources, the plots of the uv-coverage, the visibility amplitude versus uv-distance, and the high resolution image are presented. Model fit parameters to the major radio components are determined, and the brightness temperature of the core component for each source is calculated. The brightness temperature distributions for all of the sources in the VSOP AGN survey are discussed., Comment: Accepted ApJS

We present our approach of visibility modeling of disks around low-mass (< 2 M⊙) young stellar objects (YSOs). We compiled an atlas based on mid-infrared interferometric observations from the MIDI instrument at the VLTI. We use three different models to fit the data. These models allow us to determine overall sizes (and the extent of the inner gaps) of the modeled circumstellar disks.

We observed SDSS J0836+0054, the most distant radio-loud quasar known at present (z=5.774) with the European Very Long Baseline Interferometry (VLBI) Network at the 5 GHz frequency on 2003 November 4. The source is compact at the milli-arcsecond (mas) angular scale with a flux density of 0.34 mJy. The observations with the Very Large Array (VLA) made on the consecutive day support a conclusion that the radio emission from SDSS J0836+0054 is essentially confined within the central 40 pc. Based on our phase-referenced VLBI observation, we obtained the astrometric position of the source accurate to ~2 mas., 4 pages, 4 figures, accepted as Letter for A&A

We present a high resolution radio image of SDSS 0836+0054 identified recently as the most distant radio-detected quasar at a redshift of z = 5.82. The observation was carried out with ten antennas of the European VLBI Network, spread from Europe to China and South Africa, at 1.6 GHz frequency on 2002 June 8. The source is detected with a total flux density of 1.1 mJy, equal to its flux density measured in the VLA FIRST sur vey. We found no indication of multiple images produced by gravitational lensing. The radio structure of the quasar at � 10-mas angular resolution appears somewhat resolved. It resembles the radio structure typical for lower redshift radio-loud active galactic nuclei. We ob tained so far the best astrometric position of the source with an accuracy better than 8 mas, limited mainly by the structural effects in the phase-reference calibrator source.

MATISSE is the mid-infrared spectrograph and imager for the Very Large Telescope Interferometer (VLTI) at Paranal. This second generation interferometry instrument will open new avenues in the exploration of our Universe. Mid-infrared interferometry with MATISSE will allow significant advances in various fundamental research fields: studies of disks around young stellar objects where planets form and evolve, surface structures and mass loss of stars in late evolutionary stages, and the environments of black holes in active galactic nuclei. MATISSE is a unique instrument. As a first breakthrough it will enlarge the spectral domain used by optical interferometry by offering the L & M bands in addition to the N band, opening a wide wavelength domain, ranging from 2.8 to 13 μm on angular scales of 3 mas (L/M band) / 10 mas (N band). As a second breakthrough, it will allow mid-infrared imaging – closure-phase aperture-synthesis imaging – with up to four Unit Telescopes (UT) or Auxiliary Telescopes (AT) of the VLTI. MATISSE will offer various ranges of spectral resolution between R~30 to ~5000. In this article, we present some of the main science objectives that have driven the instrument design. We introduce the physical concept of MATISSE including a description of the signal on the detectors and an evaluation of the expected performance and discuss the project status. The operations concept will be detailed in a more specific future article, illustrating the observing templates operating the instrument, the data reduction and analysis, and the image reconstruction software.

The advent of extremely large telescopes will bring unprecedented light-collecting power and spatial resolution, but it will also lead to a significant increase in the size and complexity of focal-plane instruments. The use of freeform mirrors could drastically reduce the number of components in optical systems. Currently, manufacturing issues limit the common use of freeform mirrors at short wavelengths. This article outlines the use of freeform mirrors in astronomical instruments with a description of two efficient freeform optical systems. A new manufacturing method is presented which seeks to overcome the manufacturing issues through hydroforming of thin polished substrates. A specific design of an active array is detailed, which will compensate for residual manufacturing errors, thermoelastic deformation, and gravity-induced errors during observations. The combined hydroformed mirror and the active array comprise the Freeform Active Mirror Experiment, which will produce an accurate, compact, and stable freeform optics dedicated to visible and near-infrared observations., Comment: 11 pages, 12 figures

We investigate the structure of the innermost region of three circumstellar disks around pre-main sequence stars HD 142666, AS 205 N, and AS 205 S. We determine the inner radii of the dust disks and, in particular, search for transition objects where dust has been depleted and inner disk gaps have formed at radii of a few tenths of AU up to several AU. We performed interferometric observations with IOTA, AMBER, and MIDI in the infrared wavelength ranges 1.6-2.5um and 8-13um with projected baseline lengths between 25m and 102m. The data analysis was based on radiative transfer simulations in 3D models of young stellar objects (YSOs) to reproduce the spectral energy distribution and the interferometric visibilities simultaneously. Accretion effects and disk gaps could be considered in the modeling approach. Results from previous studies restricted the parameter space. The objects of this study were spatially resolved in the infrared wavelength range using the interferometers. Based on these observations, a disk gap could be found for the source HD 142666 that classifies it as transition object. There is a disk hole up to a radius of R_in=0.30AU and a (dust-free) ring between 0.35AU and 0.80AU in the disk of HD 142666. The classification of AS 205 as a system of classical T Tauri stars could be confirmed using the canonical model approach, i. e., there are no hints of disk gaps in our observations., Comment: accepted by Astronomy & Astrophysics

MATISSE is a mid-infrared spectro-interferometer combining the beams of up to four Unit Telescopes or Auxiliary Telescopes of the Very Large Telescope Interferometer (VLTI) of the European Southern Observatory. MATISSE will constitute an evolution of the two-beam interferometric instrument MIDI. New characteristics present in MATISSE will give access to the mapping and the distribution of the material, the gas and essentially the dust, in the circumstellar environments by using the mid-infrared band coverage extended to L, M and N spectral bands. The four beam combination of MATISSE provides an efficient uv-coverage: 6 visibility points are measured in one set and 4 closure phase relations which can provide aperture synthesis images in the mid-infrared spectral regime. We give an overview of the instrument including the expected performances and a view of the Science Case. We present how the instrument would be operated. The project involves the collaborations of several agencies and institutes: the Observatoire de la Cote d’Azur of Nice and the INSU-CNRS in Paris, the Max Planck Institut fur Astronomie of Heidelberg; the University of Leiden and the NOVA-ASTRON Institute of Dwingeloo, the Max Planck Institut fur Radioastronomie of Bonn, the Institut fur Theoretische Physik und Astrophysik of Kiel, the Vienna University and the Konkoly Observatory.

The Astrophysical Journal 728.1 (2011):5 reproduced by permission of the AAS, We report monitoring observations of the T Tauri star EX Lupi during its outburst in 2008 in the CO fundamental band at 4.6-5.0 μm. The observations were carried out at the Very Large Telescope and the Subaru Telescope at six epochs from 2008 April to August, covering the plateau of the outburst and the fading phase to a quiescent state. The line flux of CO emission declines with the visual brightness of the star and the continuum flux at 5 μm, but composed of two subcomponents that decay with different rates. The narrow-line emission (50 km s-1 in FWHM) is near the systemic velocity of EX Lupi. These emission lines appear exclusively in υ = 1-0. The line widths translate to a characteristic orbiting radius of 0.4 AU. The broad-line component (FWZI ∼ 150 km s-1) is highly excited up to υ ≤ 6. The line flux of the component decreases faster than the narrow-line emission. Simple modeling of the line profiles implies that the broad-line emitting gas is orbiting around the star at 0.04-0.4 AU. The excitation state, the decay speed of the line flux, and the line profile indicate that the broad-line emission component is physically distinct from the narrow-line emission component, and more tightly related to the outburst event., Zs.R. was partly supported by MO¨ B/DAAD-841 Mobility Grant. A.C. acknowledges support from a Swiss National Science Foundation grant (PP002–110504). P.A´ .Acknowledges support from the grant OTKA K62304 of the Hungarian Scientific Research Fund. The research of A´ .K. is supported by the Netherlands Organization for Scientific Research. A.S.A. acknowledges support from the Deutsche Forschungsgemeinschaft (DFG) grant SI 1486/1-1.

The Astrophysical Journal 744.2 (2012): 118 reproduced by permission of the AAS, EXLup is the prototype of the EXor class of eruptive young stars. These objects show optical outbursts which are thought to be related to runaway accretion onto the star. In a previous study we observed in situ crystal formation in the disk of EXLup during its latest outburst in 2008, making the object an ideal laboratory to investigate circumstellar crystal formation and transport. This outburst was monitored by a campaign of ground-based and Spitzer Space Telescope observations. Here we modeled the spectral energy distribution (SED) of EXLup in the outburst from optical to millimeter wavelengths with a two-dimensional radiative transfer code. Our results showed that the shape of the SED at optical wavelengths was more consistent with a single-temperature blackbody than a temperature distribution. We also found that this single-temperature component emitted 80%-100% of the total accretion luminosity. We concluded that a thermal instability, the most widely accepted model of EXor outbursts, was likely not the triggering mechanism of the 2008 outburst of EXLup. Our mid-infrared Spitzer spectra revealed that the strength of all crystalline bands between 8 and 30μm increased right after the end of the outburst. Six months later, however, the crystallinity in the 10μm silicate feature complex decreased. Our modeling of the mid-infrared spectral evolution of EXLup showed that, although vertical mixing should be stronger during the outburst than in the quiescent phase, fast radial transport of crystals (e.g., by stellar/disk wind) was required to reproduce the observed mid-infrared spectra., The research of A.K. is supported by the Netherlands Organization for Scientific Research. The research of Zs.R. is supported by the “Lendület” Young Researcher Program of the Hungarian Academy of Sciences.

The CHARA Array is funded by the National Science Foundation through NSF grants AST-0307562 and AST06006958 and by Georgia State University through the College of Arts and Sciences and the Office of the Vice President for Research. e-VLBI developments in Europe are supported by the EC DG-INFSO funded Communication Network Developments project ’EXPReS’, Contract No. 02662 (http://www.expres-eu.org/). The European VLBI Network (http://www.evlbi.org/) is a joint facility of European, Chinese, South African and other radio astronomy institutes funded by their national research councils.

MATISSE is foreseen as a mid-infrared spectro-interferometer combining the beams of up to four UTs/ATs of the Very Large Telescope Interferometer (VLTI) of the European Southern Observatory. The related science case study demonstrates the enormous capability of a new generation mid-infrared beam combiner. MATISSE will constitute an evolution of the two-beam interferometric instrument MIDI. MIDI is a very successful instrument which offers a perfect combination of spectral and angular resolution. New characteristics present in MATISSE will give access to the mapping and the distribution of the material (typically dust) in the circumstellar environments by using a wide mid-infrared band coverage extended to L, M and N spectral bands. The four beam combination of MATISSE provides an efficient UV-coverage : 6 visibility points are measured in one set and 4 closure phase relations which can provide aperture synthesis images in the mid-infrared spectral regime.

We discuss our VLBI imaging observations of J0836+0054, the highest redshift (z=5.774) radio-loud quasar known at present

We present results of an image reconstruction study in the framework of the APreS-MIDI Science Case Study [1]. We investigate image reconstruction methods of the Very Long Baseline Interferometry and the possible gains for APreS-MIDI. Different image reconstruction methods are available and can be considered depending on the future VLTI infrastructure and instrumentation.

APreS-MIDI is a concept proposed for a 10μm imaging instrument dedicated to the VLTI. It has the objective to extend the MIDI instrument to four recombined beams (see Lopez et al. [1], Dugue et al. [2]). One important step in the present phase of the instrumental study is to simulate the principle of recombination of APreS-MIDI with a model experiment. The goal is to produce laboratory data close to the ones that will be generated by APreS-MIDI. This data will be used to prepare the backbone of the future data analysis software.

Our objective is to develop of the mid-infrared imaging for the VLTI. Several areas of astrophysics will benefit of this new capability. APreS-MIDI comprises a beam combiner which interfaces with the current MIDI instrument. It thus constitutes an extension to the two-beam interferometric instrument MIDI by increasing the number of recombined beams up to four. This extension provides better uv-coverage (6 visibility points measured in one set) and moreover will allow measurement of 4 closure phase relations thus providing for the first time aperture synthesis images in the mid-infrared spectral regime.

Context: The Deep Extragalactic VLBI-Optical Survey (DEVOS) aims at constructing a large sample of compact radio sources up to two orders of magnitude fainter than those studied in other Very Long Baseline Interferometry (VLBI) surveys. Optical identification of the objects is ensured by selecting them from the Sloan Digital Sky Survey (SDSS) list. Aims: While continuing to build up the DEVOS data base, we investigated how the VLBI detection rate could be enhanced by refining the initial selection criteria introduced in the first paper of this series. Methods: We observed 26 sources in two adjacent, slightly overlapping 2 deg radius fields with the European VLBI Network (EVN) at 5 GHz frequency on 2 March 2007.The phase-reference calibrator quasars were J1616+3621 and J1623+3909. The objects selected were unresolved both in the Faint Images of the Radio Sky at Twenty-centimeters (FIRST) survey catalogue and the SDSS Data Release 4. Results: We present images of milli-arcsecond (mas) scale radio structures and accurate coordinates of 24 extragalactic sources. Most of them have never been imaged with VLBI. Twenty-two compact radio sources (85% of our initial sample) are considered as VLBI detections of the corresponding optical quasars in SDSS. We found an efficient way to identify quasars as potential VLBI targets with mas-scale compact radio stucture at >1 mJy level, based only on the FIRST and SDSS catalogue data by applying simple selection criteria., 14 pages, 7 figures (one multi-page); accepted for publication in Astronomy & Astrophysics

The young eruptive star V1647 Ori was observed with MIDI, the mid-infrared interferometric instrument at the Very Large Telescope Interferometer (VLTI), on March 2, 2005. We present the first spectrally resolved interferometric visibility points for this object. Our results show that (1) the mid-infrared emitting region is extended, having a size of ~ 7 AU at 10 um; (2) no signatures of a close companion can be seen; (3) the 8-13 um spectrum exhibits no obvious spectral features. Comparison with similar observations of Herbig Ae stars suggests that V1647 Ori probably possesses a disk of moderate flaring. A simple disk model with T ~ r^{-0.53}, \Sigma ~ r^{-1.5}, M_d = 0.05 M_Sun is able to fit both the spectral energy distribution and the observed visibility values simultaneously., Comment: 4 pages, 4 figures, accepted for publication in Astronomy and Astrophysics Letters

We present the results of the pilot observations of the Deep Extragalactic VLBI-Optical Survey (DEVOS). Our ultimate aim is to collect information on compact structures in a large sample of extragalactic radio sources (~10000 objects) up to two orders of magnitude fainter than those studied in typical imaging Very Long Baseline Interferometry (VLBI) surveys up until now. This would lead to an unprecedented data base for various astrophysical, astrometric and cosmological studies. The first global VLBI observations of the DEVOS programme were successfully conducted in May 2002. We selected sources without any spectral criterion from the Very Large Array (VLA) Faint Images of the Radio Sky at Twenty-centimeters (FIRST) catalogue, that are also detected with the Multi-Element Radio Linked Interferometer Network (MERLIN). The DEVOS pilot sample sources are in the area of the sky that is covered by the Sloan Digital Sky Survey (SDSS). We describe the sample selection and present high resolution 5-GHz radio images of the sources. Based on the results of this pilot study, we estimate the outcome of and the resources needed for a full-scale DEVOS project., Comment: 19 pages, 8 figures, accepted by A&A

Context: It is hypothesized that low-mass young stellar objects undergo eruptive phases during their early evolution. The outburst of V1647 Ori between 2003 and 2006 offered a rare opportunity to investigate such an accretion event. Aims: By means of our interferometry observing campaign during this outburst, supplemented by other observations, we investigate the temporal evolution of the inner circumstellar structure of V1647 Ori We also study the role of the changing extinction in the brightening of the object and separate it from the accretional brightening. Methods: We observed V1647 Ori with MIDI/VLTI at two epochs in this outburst. First, during the slowly fading plateau phase (2005 March) and second, just before the rapid fading of the object (2005 September), which ended the outburst. We used the radiative transfer code MC3D to fit the interferometry data and the spectral energy distributions from five different epochs at different stages of the outburst. The comparison of these models allowed us to trace structural changes in the system on AU-scales. We also considered qualitative alternatives for the interpretation of our data. Results: We found that the disk and the envelope are similar to those of non-eruptive young stars and that the accretion rate varied during the outburst. We also found evidence for the increase of the inner radii of the circumstellar disk and envelope at the beginning of the outburst. Furthermore, the change of the interferometric visibilities indicates structural changes in the circumstellar material. We test a few scenarios to interpret these data. We also speculate that the changes are caused by the fading of the central source, which is not immediately followed by the fading of the outer regions. However, if the delay in the fading of the disk is responsible for the changes seen in the MIDI data, the effect should be confirmed by dynamical modeling., 13 pages, 5 figures, accepted by A&A

Four oligomers of α-L-glutamic acid with ends blocked by nonionizable protecting groups were studied in 0.1M NaClO4 solution using potentiometric measurements. The titrations were analyzed using a pit-mapping method. The results are compared with those obtained with the corresponding polymer. The successive dissociation constants of the carboxylic side chains are obtained for oligomers with degrees of polymerization varying from 1 to 6. Then the successive stability constants corresponding to the association Cu2+–oligomer are given, and the MpHqLr distribution is calculated for each oligomer introducing MHqL complexes.

Le comportement photoelectrochimique des solutions solides de semi-conducteurs de type n Bi x Sb 2–x S 3 a ete etudie sur l’intervalle 0 2 S sur les alliages metalliques. La bande interdite varie de facon reguliere de 1,62 eV (x = 0) a 1,22 eV (x = 2) alors que le potentiel d’apparition du photocourant reste pratiquement inchange. Pour la composition x = 0,68 correspondant a la bande interdite la mieux adaptee â la conversion solaire les photoelectrodes presentent une stabilite superieure aux sulfures simples de bismuth et d’antimoine.

A simple method for preparing sulphide and selenide thin film photoelectrodes is described, using a gas-solid reaction. Results are presented for cadmium selenide electrodes, and a comparison is made with other methods of preparation.

The stability constants of the complexes of uranyl and neodymium ions with glutamic acid are determined pH-metrically in 0.1 M NaClO4 solution at 25° C. In both cases protonated complexes are formed in significant concentrations. A new MA complex is found in the uranyl glutamic acid system. In accordance with this investigation a graphical treatment of the visible spectral data gives the molar absorption coefficients of both MA and MHA species.

Solid solutions MxRu1−xS2 (M = Ni, Co, Fe) were prepared by sulphidation of mixtures of hydroxides at 673 K; their crystallographic properties were studied by X-ray diffraction. These new materials present interesting properties in biphenyl hydrogenation and in thiophene hydrodesulphurization. The catalytic properties are strongly dependent on the nature of the metal associated to ruthenium. Cobalt-ruthenium catalysts present a good activity for hydrodesulphurization but very low activity for hydrogenation, iron catalysts exhibit low activity for both reactions, and nickel catalysts possess remarkable properties in hydrogenation and hydrodesulphurization (twice the activity of pure ruthenium sulphide). A comparison has been established with the properties of molybdenum sulphide catalysts promoted by the same elements.

Preparation par une methode ceramique, activite egale ou superieure a celle de composes prepares par des methodes classiques