46 research outputs found
The diverse chemistry of protoplanetary disks as revealed by JWST
Early results from the JWST-MIRI guaranteed time programs on protostars
(JOYS) and disks (MINDS) are presented. Thanks to the increased sensitivity,
spectral and spatial resolution of the MIRI spectrometer, the chemical
inventory of the planet-forming zones in disks can be investigated with
unprecedented detail across stellar mass range and age. Here data are presented
for five disks, four around low-mass stars and one around a very young
high-mass star. The mid-infrared spectra show some similarities but also
significant diversity: some sources are rich in CO2, others in H2O or C2H2. In
one disk around a very low-mass star, booming C2H2 emission provides evidence
for a ``soot'' line at which carbon grains are eroded and sublimated, leading
to a rich hydrocarbon chemistry in which even di-acetylene (C4H2) and benzene
(C6H6) are detected (Tabone et al. 2023). Together, the data point to an active
inner disk gas-phase chemistry that is closely linked to the physical structure
(temperature, snowlines, presence of cavities and dust traps) of the entire
disk and which may result in varying CO2/H2O abundances and high C/O ratios >1
in some cases. Ultimately, this diversity in disk chemistry will also be
reflected in the diversity of the chemical composition of exoplanets.Comment: 17 pages, 8 figures. Author's version of paper submitted to Faraday
Discussions January 18 2023, Accepted March 16 202
Water in the terrestrial planet-forming zone of the PDS 70 disk
Terrestrial and sub-Neptune planets are expected to form in the inner
(AU) regions of protoplanetary disks. Water plays a key role in their
formation, although it is yet unclear whether water molecules are formed
in-situ or transported from the outer disk. So far Spitzer Space Telescope
observations have only provided water luminosity upper limits for dust-depleted
inner disks, similar to PDS 70, the first system with direct confirmation of
protoplanet presence. Here we report JWST observations of PDS 70, a benchmark
target to search for water in a disk hosting a large (AU)
planet-carved gap separating an inner and outer disk. Our findings show water
in the inner disk of PDS 70. This implies that potential terrestrial planets
forming therein have access to a water reservoir. The column densities of water
vapour suggest in-situ formation via a reaction sequence involving O, H,
and/or OH, and survival through water self-shielding. This is also supported by
the presence of CO emission, another molecule sensitive to UV
photodissociation. Dust shielding, and replenishment of both gas and small dust
from the outer disk, may also play a role in sustaining the water reservoir.
Our observations also reveal a strong variability of the mid-infrared spectral
energy distribution, pointing to a change of inner disk geometry.Comment: To appear in Nature on 24 July 2023. 21 pages, 10 figures; includes
extended data. Part of the JWST MINDS Guaranteed Time Observations program's
science enabling products. Spectra downloadable on Zenodo at
https://zenodo.org/record/799102
Adipocyte extracellular matrix composition, dynamics and role in obesity
The central role of the adipose tissue in lipid metabolism places specific demands on the cell structure of adipocytes. The protein composition and dynamics of the extracellular matrix (ECM) is of crucial importance for the functioning of those cells. Adipogenesis is a bi-phasic process in which the ECM develops from a fibrillar to a laminar structure as cells move from the commitment phase to the growth phase characterized by storage of vast amounts of triglycerides. Mature adipocytes appear to spend a lot of energy on the maintenance of the ECM. ECM remodeling is mediated by a balanced complement of constructive and destructive enzymes together with their enhancers and inhibitors. ECM remodeling is an energy costing process regulated by insulin, by the energy metabolism, and by mechanical forces. In the obese, overgrowth of adipocytes may lead to instability of the ECM, possibly mediated by hypoxia
Direct discovery of the inner exoplanet in the HD206893 system. Evidence for deuterium burning in a planetary-mass companion
Long term precise radial velocity (RV) monitoring of the nearby star
HD206893, as well as anomalies in the system proper motion, have suggested the
presence of an additional, inner companion in the system. Here we describe the
results of a multi-epoch search for the companion responsible for this RV drift
and proper motion anomaly using the VLTI/GRAVITY instrument. Utilizing
information from ongoing precision RV measurements with the HARPS spectrograph,
as well as Gaia host star astrometry, we report a high significance detection
of the companion HD206893c over three epochs, with clear evidence for Keplerian
orbital motion. Our astrometry with 50-100 arcsec precision afforded
by GRAVITY allows us to derive a dynamical mass of 12.7 M and an orbital separation of 3.53 au for HD206893c. Our
fits to the orbits of both companions in the system utilize both Gaia
astrometry and RVs to also provide a precise dynamical estimate of the
previously uncertain mass of the B component, and therefore derive an age of
Myr. We find that theoretical atmospheric/evolutionary models
incorporating deuterium burning for HD206893c, parameterized by cloudy
atmospheres provide a good simultaneous fit to the luminosity of both HD206893B
and c. In addition to utilizing long-term RV information, this effort is an
early example of a direct imaging discovery of a bona fide exoplanet that was
guided in part with Gaia astrometry. Utilizing Gaia astrometry is expected to
be one of the primary techniques going forward to identify and characterize
additional directly imaged planets. Lastly, this discovery is another example
of the power of optical interferometry to directly detect and characterize
extrasolar planets where they form at ice-line orbital separations of 2-4\,au.Comment: Accepted to A&
20-Year Risks of Breast-Cancer Recurrence after Stopping Endocrine Therapy at 5 Years
The administration of endocrine therapy for 5 years substantially reduces recurrence rates during and after treatment in women with early-stage, estrogen-receptor (ER)-positive breast cancer. Extending such therapy beyond 5 years offers further protection but has additional side effects. Obtaining data on the absolute risk of subsequent distant recurrence if therapy stops at 5 years could help determine whether to extend treatment
Increased adipose tissue expression of lipocalin-2 in obesity is related to inflammation and matrix metalloproteinase-2 and metalloproteinase-9 activities in humans
The mass of β Pictoris c from β Pictoris b orbital motion
Aims. We aim to demonstrate that the presence and mass of an exoplanet can now be effectively derived from the astrometry of another exoplanet. Methods. We combined previous astrometry of β Pictoris b with a new set of observations from the GRAVITY interferometer. The orbital motion of β Pictoris b is fit using Markov chain Monte Carlo simulations in Jacobi coordinates. The inner planet, β Pictoris c, was also reobserved at a separation of 96 mas, confirming the previous orbital estimations. Results. From the astrometry of planet b only, we can (i) detect the presence of β Pictoris c and (ii) constrain its mass to 10.04-3.10+4.53 MJup. If one adds the astrometry of β Pictoris c, the mass is narrowed down to 9.15-1.06+1.08 MJup. The inclusion of radial velocity measurements does not affect the orbital parameters significantly, but it does slightly decrease the mass estimate to 8.89-0.75+0.75 MJup. With a semimajor axis of 2.68 ± 0.02 au, a period of 1221 ± 15 days, and an eccentricity of 0.32 ± 0.02, the orbital parameters of β Pictoris c are now constrained as precisely as those of β Pictoris b. The orbital configuration is compatible with a high-order mean-motion resonance (7:1). The impact of the resonance on the planets' dynamics would then be negligible with respect to the secular perturbations, which might have played an important role in the eccentricity excitation of the outer planet. © 2021 S. Lacour et al
Valorisation of Biowastes for the Production of Green Materials Using Chemical Methods
With crude oil reserves dwindling, the hunt for a sustainable alternative feedstock for fuels and materials for our society continues to expand. The biorefinery concept has enjoyed both a surge in popularity and also vocal opposition to the idea of diverting food-grade land and crops for this purpose. The idea of using the inevitable wastes arising from biomass processing, particularly farming and food production, is, therefore, gaining more attention as the feedstock for the biorefinery. For the three main components of biomass—carbohydrates, lipids, and proteins—there are long-established processes for using some of these by-products. However, the recent advances in chemical technologies are expanding both the feedstocks available for processing and the products that be obtained. Herein, this review presents some of the more recent developments in processing these molecules for green materials, as well as case studies that bring these technologies and materials together into final products for applied usage