71 research outputs found
Imaging of Dysfunctional Elastogenesis in Atherosclerosis Using an Improved Gadolinium-Based Tetrameric MRI Probe Targeted to Tropoelastin
Dysfunctional elastin turnover plays a major role in the progression of atherosclerotic plaques. Failure of tropoelastin cross-linking into mature elastin leads to the accumulation of tropoelastin within the growing plaque, increasing its instability. Here we present Gd4-TESMA, an MRI contrast agent specifically designed for molecular imaging of tropoelastin within plaques. Gd4-TESMA is a tetrameric probe composed of a tropoelastin-binding peptide (the VVGS-peptide) conjugated with four Gd(III)-DOTA-monoamide chelates. It shows a relaxivity per molecule of 34.0 ± 0.8 mM-1 s-1 (20 MHz, 298 K, pH 7.2), a good binding affinity to tropoelastin (KD = 41 ± 12 μM), and a serum half-life longer than 2 h. Gd4-TESMA accumulates specifically in atherosclerotic plaques in the ApoE-/- murine model of plaque progression, with 2 h persistence of contrast enhancement. As compared to the monomeric counterpart (Gd-TESMA), the tetrameric Gd4-TESMA probe shows a clear advantage regarding both sensitivity and imaging time window, allowing for a better characterization of atherosclerotic plaques
SUBARU prime focus spectrograph: integration, testing and performance for the first spectrograph
The Prime Focus Spectrograph (PFS) of the Subaru Measurement of Images and
Redshifts (SuMIRe) project for Subaru telescope consists in four identical
spectrographs fed by 600 fibers each. Each spectrograph is composed by an
optical entrance unit that creates a collimated beam and distributes the light
to three channels, two visibles and one near infrared. This paper presents the
on-going effort for the tests & integration process for the first spectrograph
channel: we have developed a detailed Assembly Integration and Test (AIT) plan,
as well as the methods, detailed processes and I&T tools. We describe the tools
we designed to assemble the parts and to test the performance of the
spectrograph. We also report on the thermal acceptance tests we performed on
the first visible camera unit. We also report on and discuss the technical
difficulties that did appear during this integration phase. Finally, we detail
the important logistic process that is require to transport the components from
other country to Marseille
First light of VLT/HiRISE: High-resolution spectroscopy of young giant exoplanets
A major endeavor of this decade is the direct characterization of young giant exoplanets at high spectral resolution to determine the composition of their atmosphere and infer their formation processes and evolution. Such a goal represents a major challenge owing to their small angular separation and luminosity contrast with respect to their parent stars. Instead of designing and implementing completely new facilities, it has been proposed to leverage the capabilities of existing instruments that offer either high-contrast imaging or high-dispersion spectroscopy by coupling them using optical fibers. In this work, we present the implementation and first on-sky results of the High-Resolution Imaging and Spectroscopy of Exoplanets (HiRISE) instrument at the Very Large Telescope (VLT), which combines the exoplanet imager SPHERE with the recently upgraded high-resolution spectrograph CRIRES using single-mode fibers. The goal of HiRISE is to enable the characterization of known companions in the H band at a spectral resolution on the order of R = λ/∆λ = 100 000 in a few hours of observing time. We present the main design choices and the technical implementation of the system, which is constituted of three major parts: the fiber injection module inside of SPHERE, the fiber bundle around the telescope, and the fiber extraction module at the entrance of CRIRES. We also detail the specific calibrations required for HiRISE and the operations of the instrument for science observations. Finally, we detail the performance of the system in terms of astrometry, temporal stability, optical aberrations, and transmission, for which we report a peak value of ~3.9% based on sky measurements in median observing conditions. Finally, we report on the first astrophysical detection of HiRISE to illustrate its potential
First light of VLT/HiRISE: High-resolution spectroscopy of young giant exoplanets
A major endeavor of this decade is the direct characterization of young giant
exoplanets at high spectral resolution to determine the composition of their
atmosphere and infer their formation processes and evolution. Such a goal
represents a major challenge owing to their small angular separation and
luminosity contrast with respect to their parent stars. Instead of designing
and implementing completely new facilities, it has been proposed to leverage
the capabilities of existing instruments that offer either high contrast
imaging or high dispersion spectroscopy, by coupling them using optical fibers.
In this work we present the implementation and first on-sky results of the
HiRISE instrument at the very large telescope (VLT), which combines the
exoplanet imager SPHERE with the recently upgraded high resolution spectrograph
CRIRES using single-mode fibers. The goal of HiRISE is to enable the
characterization of known companions in the band, at a spectral resolution
of the order of , in a few hours of
observing time. We present the main design choices and the technical
implementation of the system, which is constituted of three major parts: the
fiber injection module inside of SPHERE, the fiber bundle around the telescope,
and the fiber extraction module at the entrance of CRIRES. We also detail the
specific calibrations required for HiRISE and the operations of the instrument
for science observations. Finally, we detail the performance of the system in
terms of astrometry, temporal stability, optical aberrations, and transmission,
for which we report a peak value of 3.9% based on sky measurements in
median observing conditions. Finally, we report on the first astrophysical
detection of HiRISE to illustrate its potential.Comment: 17 pages, 15 figures, 3 tables. Submitted to A&A on 19 September 202
Emission of volatile halogenated compounds, speciation and localization of bromine and iodine in the brown algal genome model Ectocarpus siliculosus
This study explores key features of bromine and iodine metabolism in the filamentous brown alga and genomics model Ectocarpus siliculosus. Both elements are accumulated in Ectocarpus, albeit at much lower concentration factors (2-3 orders of magnitude for iodine, and < 1 order of magnitude for bromine) than e.g. in the kelp Laminaria digitata. Iodide competitively reduces the accumulation of bromide. Both iodide and bromide are accumulated in the cell wall (apoplast) of Ectocarpus, with minor amounts of bromine also detectable in the cytosol. Ectocarpus emits a range of volatile halogenated compounds, the most prominent of which by far is methyl iodide. Interestingly, biosynthesis of this compound cannot be accounted for by vanadium haloperoxidase since the latter have not been found to catalyze direct halogenation of an unactivated methyl group or hydrocarbon so a methyl halide transferase-type production mechanism is proposed
Prime Focus Spectrograph (PFS) for the Subaru telescope: Ongoing integration and future plans
PFS (Prime Focus Spectrograph), a next generation facility instrument on the 8.2-meter Subaru Telescope, is a very wide-field, massively multiplexed, optical and near-infrared spectrograph. Exploiting the Subaru prime focus, 2394 reconfigurable fibers will be distributed over the 1.3 deg field of view. The spectrograph has been designed with 3 arms of blue, red, and near-infrared cameras to simultaneously observe spectra from 380nm to 1260nm in one exposure at a resolution of ∼ 1.6-2.7Å. An international collaboration is developing this instrument under the initiative of Kavli IPMU. The project recently started undertaking the commissioning process of a subsystem at the Subaru Telescope side, with the integration and test processes of the other subsystems ongoing in parallel. We are aiming to start engineering night-sky operations in 2019, and observations for scientific use in 2021. This article gives an overview of the instrument, current project status and future paths forward
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