148 research outputs found
Wind loads analysis at the anchorages of the Talavera de la Reina cable stayed bridge
This paper describes wind tunnel tests performed on wind tunnel models of the Talavera de la Reina cable stayed bridge. The work describes the aeroelastic model construction and it is focused on the evaluation and analysis of the mean and peak wind loads at the tower foundation and the cable anchorages since these data can be very useful by the bridge manufacturer as a support for the bridge design. The work is part of a complete wind tunnel study carried out to analyze the aeroelastic stability of the bridge
Learning to Teach through Self-Awareness and Acceptance
This article is an account of my first teaching experience as a PhD student. It is the story of my
personal journey toward self-discovery in which I learned to integrate my clinical social work
skills into my teaching. This article details a variety of emotions and struggles experienced both
by my students and myself. This narrative describes how I came to be a more conscientious
instructor, how I learned to link lessons from the clinical world to my teaching, and how my
learning process included significant advances of self-discovery and personal growth. Through
this experience, I came to understand that pedagogy and clinical techniques can dovetail,
demonstrating the need to individualize interventions, build community with stakeholders, and
foster trusting relationships
Dealing with adversity: religiosity or science? Evidence from the great influenza pandemic
How do societies respond to adversity? After a negative shock, separate strands of research document either an increase in religiosity or a boost in innovation efforts. In this paper, we show that both reactions can occur at the same time, driven by different individuals within society. The setting of our study is the 1918-1919 influenza pandemic in the United States. To measure religiosity, we construct a novel indicator based on naming patterns of newborns. We measure innovation through the universe of granted patents. Exploiting plausibly exogenous county-level variation in exposure to the pandemic, we provide evidence that more-affected counties become both more religious and more innovative. Looking within counties, we uncover heterogeneous responses: individuals from more religious backgrounds further embrace religion, while those from less religious backgrounds become more likely to choose a scientific occupation. Facing adversity widens the distance in religiosity between science-oriented individuals and the rest of the population, and it increases the polarization of religious beliefs
Stellar companions and Jupiter-like planets in young associations
Recently, combining high-contrast imaging and space astrometry we found that
Jupiter-like (JL) planets are frequent in the beta Pic moving group (BPMG)
around those stars where their orbit can be stable, prompting further analysis
and discussion. We broaden our previous analysis to other young nearby
associations to determine the frequency, mass, and separation of companions in
general and JL in particular and their dependencies on the mass and age of the
associations. We collected available data about companions including those
revealed by visual observations, eclipses, spectroscopy, and astrometry. We
determined search completeness and found that it is very high for stellar
companions, while completeness corrections are still large for JL companions.
Once these corrections are included, we found a high frequency of companions,
both stellar (>0.52+/-0.03) and JL (0.57+/-0.11). The two populations are
separated by a gap that corresponds to the brown dwarf desert. Within the
population of massive companions, we found trends in frequency, separation, and
mass ratios with stellar mass. Planetary companions pile up in the region just
outside the ice line and we found them to be frequent once completeness was
considered. The frequency of JL planets decreases with the overall mass and
possibly the age of the association. We tentatively identify the two
populations as due to disk fragmentation and core accretion, respectively. The
distributions of stellar companions with a semi-major axis <1000 au is well
reproduced by a simple model of formation by disk fragmentation. The observed
trends with stellar mass can be explained by a shorter but much more intense
phase of accretion onto the disk of massive stars and by a more steady and
prolonged accretion on solar-type stars. Possible explanations for the trends
in the population of JL planets with association mass and age are briefly
discussed.Comment: Accepted by Astronomy and Astrophysics, 52 pages, 23 figure
An imaged 15Mjup companion within a hierarchical quadruple system
Since 2019, the direct imaging B-star Exoplanet Abundance Study (BEAST) at
SPHERE@VLT has been scanning the surroundings of young B-type stars in order to
ascertain the ultimate frontiers of giant planet formation. Recently, the
Myr HIP 81208 was found to host a close-in (~50 au) brown dwarf
and a wider (~230 au) late M star around the central 2.6Msun primary. Alongside
the continuation of the survey, we are undertaking a complete reanalysis of
archival data aimed at improving detection performances so as to uncover
additional low-mass companions. We present here a new reduction of the
observations of HIP 81208 using PACO ASDI, a recent and powerful algorithm
dedicated to processing high-contrast imaging datasets, as well as more
classical algorithms and a dedicated PSF-subtraction approach. The combination
of different techniques allowed for a reliable extraction of astrometric and
photometric parameters. A previously undetected source was recovered at a short
separation from the C component of the system. Proper motion analysis provided
robust evidence for the gravitational bond of the object to HIP 81208 C.
Orbiting C at a distance of ~20 au, this 15Mjup brown dwarf becomes the fourth
object of the hierarchical HIP 81208 system. Among the several BEAST stars
which are being found to host substellar companions, HIP 81208 stands out as a
particularly striking system. As the first stellar binary system with
substellar companions around each component ever found by direct imaging, it
yields exquisite opportunities for thorough formation and dynamical follow-up
studies.Comment: 12 pages, 9 figures, 5 tables. Accepted for publication as a Letter
in Astronomy and Astrophysics, section 1. Letters to the Edito
Implications of the discovery of AF Lep b. The mass-luminosity relation for planets in the ÎČ Pic Moving Group and the LâT transition for young companions and free-floating planets
This is the final version. Available on open access from EDP Sciences via the DOI in this recordContext. Dynamical masses of young planets aged between 10 and 200 Myr detected in imaging play a crucial role in shaping models of giant planet formation. Regrettably, only a few such objects possess these characteristics. Furthermore, the evolutionary pattern of young sub-stellar companions in near-infrared colour-magnitude diagrams might diverge from free-floating objects, possibly due to differing formation processes.
Aims. The recent identification of a giant planet around AF Lep, part of the ÎČ Pic moving group (BPMG), encouraged us to re-examine these points.
Methods. We considered updated dynamical masses and luminosities for the sub-stellar objects in the BPMG. In addition, we compared the properties of sub-stellar companions and free-floating objects in the BPMG and other young associations remapping the positions of the objects in the colour-magnitude diagram into a dustiness-temperature plane.
Results. We found that cold-start evolutionary models do not reproduce the mass-luminosity relation for sub-stellar companions in the BPMG. This aligns rather closely with predictions from âhot startâ scenarios and is consistent with recent planet formation models. We obtain rather good agreement with masses from photometry and the remapping approach compared to actual dynamical masses. We also found a strong suggestion that the near-infrared colour-magnitude diagram for young companions is different from that of free-floating objects belonging to the same young associations.
Conclusions. If confirmed by further data, this last result would imply that cloud settling â which likely causes the transition between L and T spectral type â occurs at a lower effective temperature in young companions than in free-floating objects. This might tentatively be explained with a different chemical composition.Royal Societ
TOI-179: a young system with a transiting compact Neptune-mass planet and a low-mass companion in outer orbit
Transiting planets around young stars are key benchmarks for our
understanding of planetary systems. One of such candidates was identified
around the K dwarf HD 18599 by TESS, labeled as TOI-179. We present the
confirmation of the transiting planet and the characterization of the host star
and of the TOI-179 system over a broad range of angular separations. To this
aim, we exploited the TESS photometric time series, intensive radial velocity
monitoring performed with HARPS, and deep high-contrast imaging observations
obtained with SPHERE and NACO at VLT. The inclusion of Gaussian processes
regression analysis is effective to properly model the magnetic activity of the
star and identify the Keplerian signature of the transiting planet. The star,
with an age of 400+-100 Myr, is orbited by a transiting planet with period
4.137436 days, mass 24+-7 Mearth, radius 2.62 (+0.15-0.12) Rearth, and
significant eccentricity (0.34 (+0.07-0.09)). Adaptive optics observations
identified a low-mass companion at the boundary between brown dwarfs and very
low mass stars (mass derived from luminosity 83 (+4-6) Mjup) at a very small
projected separation (84.5 mas, 3.3 au at the distance of the star). Coupling
the imaging detection with the long-term radial velocity trend and the
astrometric signature, we constrained the orbit of the low mass companion,
identifying two families of possible orbital solutions. The TOI-179 system
represents a high-merit laboratory for our understanding of the physical
evolution of planets and other low-mass objects and of how the planet
properties are influenced by dynamical effects and interactions with the parent
star.Comment: 25 pages, 24 figures, A&A, in pres
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