72 research outputs found
Improved Screening of cDNAs Generated by mRNA Differential Display Enables the Selection of True Positives and the Isolation of Weakly Expressed Messages
The high percentage of false positives generated by differential display (as
high as 85%) has previously limited the potential of the method. This report describes
an efficient methodology that enables false positives to be discarded prior to cloning, via
reverse Northern analysis. This first step of the screening also allows the detection of
putative lowabundance differential clones. Following cloning, a second reverseNorthern
combined with partial DNA sequencing and RT-PCR detection allows isolation of all
differential cDNAs including very lowabundance clones. Use of the sequential screening
procedure described here led to the isolation of novel tomato genes responding to the
plant hormone ethylene while minimising labor and materials input
Sculpting the disk around T Cha: an interferometric view
(Abridged) Circumstellar disks are believed to be the birthplace of planets
and are expected to dissipate on a timescale of a few Myr. The processes
responsible for the removal of the dust and gas will strongly modify the radial
distribution of the dust and consequently the SED. In particular, a young
planet will open a gap, resulting in an inner disk dominating the near-IR
emission and an outer disk emitting mostly in the far-IR. We analyze a full set
of data (including VLTI/Pionier, VLTI/Midi, and VLT/NaCo/Sam) to constrain the
structure of the transition disk around TCha. We used the Mcfost radiative
transfer code to simultaneously model the SED and the interferometric
observations. We find that the dust responsible for the emission in excess in
the near-IR must have a narrow temperature distribution with a maximum close to
the silicate sublimation temperature. This translates into a narrow inner dusty
disk (0.07-0.11 AU). We find that the outer disk starts at about 12 AU and is
partially resolved by the Pionier, Sam, and Midi instruments. We show that the
Sam closure phases, interpreted as the signature of a candidate companion, may
actually trace the asymmetry generated by forward scattering by dust grains in
the upper layers of the outer disk. These observations help constrain the
inclination and position angle of the outer disk. The presence of matter inside
the gap is difficult to assess with present-day observations. Our model
suggests the outer disk contaminates the interferometric signature of any
potential companion that could be responsible for the gap opening, and such a
companion still has to be unambiguously detected. We stress the difficulty to
observe point sources in bright massive disks, and the consequent need to
account for disk asymmetries (e.g. anisotropic scattering) in model-dependent
search for companions.Comment: Removed the word "first" in the abstract of the paper: "obtained with
the first 4-telescope combiner (VLTI/Pionier)
X-shooter, NACO, and AMBER observations of the LBV Pistol Star \footnote{Based on ESO runs 85.D-0182A, 085.D-0625AC}
We present multi-instruments and multi-wavelengths observations of the famous
LBV star Pistol Star. These observations are part of a larger program about
early O stars at different metallicities. The Pistol star has been claimed as
the most massive star known, with 250 solar masses. We present the preliminary
results based on X-Shooter spectra, as well as the observations performed with
the VLTI-AMBER and the VLT-NACO adaptive optics. The X-shooter spectrograph
allows to obtain simultaneously a spectrum from the UV to the K-band with a
resolving power of 15000. The preliminary results obtained indicate that
Pistol Star has similar properties of Eta Car, including shells of matter, but
also the binarity. Other objects of the program, here briefly presented, were
selected for their particular nature: early O stars with mass discrepancies
between stellar evolution models and observations, discrepancies with the wind
momentum luminosity relation.Comment: Poster at the 39th LIAC, submitted version of the proceeding
High-angular resolution observations of the Pistol Star
First results of near-IR adaptive optics (AO)-assisted imaging,
interferometry, and spectroscopy of this Luminous Blue Variable (LBV) are
presented. They suggest that the Pistol Star is at least double. If the
association is physical, it would reinforce questions concerning the importance
of multiplicity for the formation and evolution of extremely massive stars.Comment: poster at IAUS27
Luminous blue variables: An imaging perspective on their binarity and near environment
Luminous blue variables (LBVs) are rare massive stars with very high
luminosity. They are characterized by strong photo-metric and spectroscopic
variability related to transient eruptions. The mechanisms at the origin of
these eruptions is not well known. In addition, their formation is still
problematic and the presence of a companion could help to explain how they
form. Aims. This article presents a study of seven LBVs (about 20% of the known
Galactic population), some Wolf-Rayet stars, and massive binaries. We probe the
environments that surround these massive stars with near-, mid-, and
far-infrared images, investigating potential nebula/shells and the companion
stars. Methods. To investigate large spatial scales, we used seeing-limited and
near diffraction-limited adaptive optics images to obtain a differential
diagnostic on the presence of circumstellar matter and to determine their
extent. From those images, we also looked for the presence of binary companions
on a wide orbit. Once a companion was detected, its gravitational binding to
the central star was tested. Tests include the chance projection probability,
the proper motion estimates with multi-epoch observations, flux ratio, and star
separations. Results. We find that two out of seven of LBVs may have a wide
orbit companion. Most of the LBVs display a large circumstellar envelope or
several shells. In particular, HD168625, known for its rings, possesses several
shells with possibly a large cold shell at the edge of which the rings are
formed. For the first time, we have directly imaged the companion of LBV stars
The planar optics phase sensor: a study for the VLTI 2nd generation fringe tracker
In a few years, the second generation instruments of the Very Large Telescope Interferometer (VLTI) will routinely provide observations with 4 to 6 telescopes simultaneously. To reach their ultimate performance, they will need a fringe sensor capable to measure in real time the randomly varying optical paths differences. A collaboration between LAOG (PI institute), IAGL, OCA and GIPSA-Lab has proposed the Planar Optics Phase Sensor concept to ESO for the 2[SUP]nd[/SUP] Generation Fringe Tracker. This concept is based on the integrated optics technologies, enabling the conception of extremely compact interferometric instruments naturally providing single-mode spatial filtering. It allows operations with 4 and 6 telescopes by measuring the fringes position thanks to a spectrally dispersed ABCD method. We present here the main analysis which led to the current concept as well as the expected on-sky performance and the proposed design
The orbit and stellar masses of the archetype colliding-wind binary WR 140
We present updated orbital elements for the Wolf-Rayet (WR) binary WR 140 (HD
193793; WC7pd + O5.5fc). The new orbital elements were derived using previously
published measurements along with 160 new radial velocity measurements across
the 2016 periastron passage of WR 140. Additionally, four new measurements of
the orbital astrometry were collected with the CHARA Array. With these
measurements, we derive stellar masses of
and . We also include a discussion of the
evolutionary history of this system from the Binary Population and Spectral
Synthesis (BPASS) model grid to show that this WR star likely formed primarily
through mass loss in the stellar winds, with only a moderate amount of mass
lost or transferred through binary interactions.Comment: 10 pages, 5 figure
Elm1 kinase activates the spindle position checkpoint kinase Kin4
Elm1 phosphorylates a conserved residue within the Kin4 kinase domain to coordinate spindle position with cell cycle progression
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