123 research outputs found
Gaia view of low-mass star formation
Understanding how young stars and their circumstellar disks form and evolve
is key to explain how planets form. The evolution of the star and the disk is
regulated by different processes, both internal to the system or related to
their environment. The former include accretion of material onto the central
star, wind emission, and photoevaporation of the disk due to high-energy
radiation from the central star. These are best studied spectroscopically, and
the distance to the star is a key parameter in all these studies. Here we
present new estimates of the distance to a complex of nearby star-forming
clouds obtained combining TGAS distances with measurement of extinction on the
line of sight. Furthermore, we show how we plan to study the effects of the
environment on the evolution of disks with Gaia, using a kinematic modelling
code we have developed to model young star-forming regions.Comment: 4 pages, 1 figure. To appear in the Proceedings of IAU Symposium 330:
Astrometry and Astrophysics in the Gaia Sk
3D mapping of young stars in the solar neighbourhood with Gaia DR2
We study the three dimensional arrangement of young stars in the solar
neighbourhood using the second release of the Gaia mission (Gaia DR2) and we
provide a new, original view of the spatial configuration of the star forming
regions within 500 pc from the Sun. By smoothing the star distribution through
a gaussian filter, we construct three dimensional density maps for early-type
stars (upper-main sequence, UMS) and pre-main sequence (PMS) sources. The PMS
and the UMS samples are selected through a combination of photometric and
astrometric criteria. A side product of the analysis is a three dimensional,
G-band extinction map, which we use to correct our colour-magnitude diagram for
extinction and reddening. Both density maps show three prominent structures,
Scorpius-Centaurus, Orion, and Vela. The PMS map shows a plethora of lower mass
star forming regions, such as Taurus, Perseus, Cepheus, Cassiopeia, and
Lacerta, which are less visible in the UMS map, due to the lack of large
numbers of bright, early-type stars. We report the finding of a candidate new
open cluster towards , which could be
related to the Orion star forming complex. We estimate ages for the PMS sample
and we study the distribution of PMS stars as a function of their age. We find
that younger stars cluster in dense, compact clumps, and are surrounded by
older sources, whose distribution is instead more diffuse. The youngest groups
that we find are mainly located in Scorpius-Centaurus, Orion, Vela, and Taurus.
Cepheus, Cassiopeia, and Lacerta are instead more evolved and less numerous.
Finally, we find that the three dimensional density maps show no evidence for
the existence of the ring-like structure which is usually referred to as the
Gould Belt.Comment: 17 pages, 17 figures, 6 appendixes; accepted for publication in A&A;
image quality decreased to comply with the arXiv.org rules on file siz
Mapping young stellar populations towards Orion with Gaia DR1
We use the first data release of the Gaia mission to explore the three
dimensional arrangement and the age ordering of the many stellar groups towards
the Orion OB association, aiming at a new classification and characterization
of the stellar population. We make use of the parallaxes and proper motions
provided in the Tycho Gaia Astrometric Solution (TGAS) sub-set of the Gaia
catalogue, and of the combination of Gaia and 2MASS photometry. In TGAS we find
evidence for the presence of a young population, at a parallax , loosely distributed around some known clusters: 25 Ori,
Ori and Ori, and NGC 1980 ( Ori). The low mass
counterpart of this population is visible in the color-magnitude diagrams
constructed by combining Gaia and 2MASS photometry. We study the density
distribution of the young sources in the sky. We find the same groups as in
TGAS, and also some other density enhancements that might be related to the
recently discovered Orion X group, the Orion dust ring, and to the
Ori complex. We estimate the ages of this population and we infer the presence
of an age gradient going from 25 Ori (13-15 Myr) to the ONC (1-2 Myr). We
confirm this age ordering by repeating the Bayesian fit using the Pan-STARRS1
data. The estimated ages towards the NGC 1980 cluster span a broad range of
values. This can either be due to the presence of two populations coming from
two different episodes of star formation or to a large spread along the line of
sight of the same population. Our results form the first step towards using the
Gaia data to unravel the complex star formation history of the Orion region in
terms of the different star formation episodes, their duration, and their
effects on the surrounding interstellar medium.Comment: 17 pages, 17 figure
3D shape of Orion A from Gaia DR2
Reproduced with permission from Astronomy & Astrophysics. © 2018 ESO.We use the Gaia DR2 distances of about 700 mid-infrared selected young stellar objects in the benchmark giant molecular cloud Orion A to infer its 3D shape and orientation. We find that Orion A is not the fairly straight filamentary cloud that we see in (2D) projection, but instead a cometary-like cloud oriented toward the Galactic plane, with two distinct components: a denser and enhanced star-forming (bent) Head, and a lower density and star-formation quieter ~75 pc long Tail. The true extent of Orion A is not the projected ~40 pc but ~90 pc, making it by far the largest molecular cloud in the local neighborhood. Its aspect ratio (~30:1) and high column-density fraction (~45%) make it similar to large-scale Milky Way filaments ("bones"), despite its distance to the galactic mid-plane being an order of magnitude larger than typically found for these structures.Peer reviewedFinal Accepted Versio
New loci for body fat percentage reveal link between adiposity and cardiometabolic disease risk
To increase our understanding of the genetic basis of adiposity and its links to cardiometabolic disease risk, we conducted a genome-wide association meta-analysis of body fat percentage (BF%) in up to 100,716 individuals. Twelve loci reached genome-wide significance (P\u3c5 × 10−8), of which eight were previously associated with increased overall adiposity (BMI, BF%) and four (in or near COBLL1/GRB14, IGF2BP1, PLA2G6, CRTC1) were novel associations with BF%. Seven loci showed a larger effect on BF% than on BMI, suggestive of a primary association with adiposity, while five loci showed larger effects on BMI than on BF%, suggesting association with both fat and lean mass. In particular, the loci more strongly associated with BF% showed distinct cross-phenotype association signatures with a range of cardiometabolic traits revealing new insights in the link between adiposity and disease risk
A comparison of the Milky Way's recent star formation revealed by dust thermal emission and high-mass stars
We present a comparison of the Milky Way's star formation rate (SFR) surface
density () obtained with two independent state-of-the-art
observational methods. The first method infers from the
observations of the dust thermal emission from interstellar dust grains in far
infrared wavelengths registered in the Herschel Infrared Galactic Plane Survey
(Hi-GAL), as presented in Elia et al. (2022). The second method obtains
by modeling the current population of O-, B-, and A-type
stars in a 6 kpc 6 kpc area around the Sun, as presented in Zari et
al. (2023). We found an agreement between the two methods within a factor of
two for the mean SFRs and the SFR surface density profiles. Given the broad
differences between the observational techniques and the independent
assumptions in the methods to compute the SFRs, this agreement constitutes a
significant advance in our understanding of the star formation of our Galaxy
and implies that the local SFR has been roughly constant over the past 10 Myr.Comment: Submitted to A&A (31JUL2023). 8 pages, 7 figures. Comments are
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Current engineering developments for robotic systems in flexible endoscopy
The past four decades have seen an increase in the incidence of early-onset gastrointestinal cancer. Because early-stage cancer detection is vital to reduce mortality rate, mass screening colonoscopy provides the most effective prevention strategy. However, conventional endoscopy is a painful and technically challenging procedure that requires sedation and experienced endoscopists to be performed. To overcome the current limitations, technological innovation is needed in colonoscopy. In recent years, researchers worldwide have worked to enhance the diagnostic and therapeutic capabilities of endoscopes. The new frontier of endoscopic interventions is represented by robotic flexible endoscopy. Among all options, self-propelling soft endoscopes are particularly promising thanks to their dexterity and adaptability to the curvilinear gastrointestinal anatomy. For these devices to replace the standard endoscopes, integration with embedded sensors and advanced surgical navigation technologies must be investigated. In this review, the progress in robotic endoscopy was divided into the fundamental areas of design, sensing, and imaging. The article offers an overview of the most promising advancements on these three topics since 2018. Continuum endoscopes, capsule endoscopes, and add-on endoscopic devices were included, with a focus on fluid-driven, tendon-driven, and magnetic actuation. Sensing methods employed for the shape and force estimation of flexible endoscopes were classified into model- and sensor-based approaches. Finally, some key contributions in molecular imaging technologies, artificial neural networks, and software algorithms are described. Open challenges are discussed to outline a path toward clinical practice for the next generation of endoscopic devices
A Facile Method for the Non-Covalent Amine Functionalization of Carbon-Based Surfaces for Use in Biosensor Development
Affinity biosensors based on graphene field-effect transistor (GFET) or resistor designs require the utilization of graphene’s exceptional electrical properties. Therefore, it is critical when designing these sensors, that the electrical properties of graphene are maintained throughout the functionalization process. To that end, non-covalent functionalization may be preferred over covalent modification. Drop-cast 1,5-diaminonaphthalene (DAN) was investigated as a quick and simple method for the non-covalent amine functionalization of carbon-based surfaces such as graphene, for use in biosensor development. In this work, multiple graphene surfaces were functionalized with DAN via a drop-cast method, leading to amine moieties, available for subsequent attachment to receptor molecules. Successful modification of graphene with DAN via a drop-cast method was confirmed using X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and real-time resistance measurements. Successful attachment of receptor molecules also confirmed using the aforementioned techniques. Furthermore, an investigation into the effect of sequential wash steps which are required in biosensor manufacture, on the presence of the DAN layer, confirmed that the functional layer was not removed, even after multiple solvent exposures. Drop-cast DAN is thus, a viable fast and robust method for the amine functionalization of graphene surfaces for use in biosensor development
The Causal Effect of Vitamin D Binding Protein (DBP) Levels on Calcemic and Cardiometabolic Diseases: A Mendelian Randomization Study
Background: Observational studies have shown that vitamin D binding protein (DBP) levels, a key determinant of 25-hydroxy- vitamin D (25OHD) levels, and 25OHD levels themselves both associate with risk of disease. If 25OHD levels have a causal influence on disease, and DBP lies in this causal pathway, then DBP levels should likewise be causally associated with disease. We undertook a Mendelian randomization study to determine whether DBP levels have causal effects on common calcemic and cardiometabolic disease. Methods and Findings: We measured DBP and 25OHD levels in 2,254 individuals, followed for up to 10 y, in the Canadian Multicentre Osteoporosis Study (CaMos). Using the single nucleotide polymorphism rs2282679 as an instrumental variable, we applied Mendelian randomization methods to determine the causal effect of DBP on calcemic (osteoporosis and hyperparathyroidism) and cardiometabolic diseases (hypertension, type 2 diabetes, coronary artery disease, and stroke) and related traits, first in CaMos and then in large-scale genome-wide association study consortia. The effect allele was associated with an age-and sex-adjusted decrease in DBP level of 27.4 mg/l (95% CI 24.7, 30.0; n=2,254). DBP had a strong observational and causal association with 25OHD levels (p=3.2x10(-19)). While DBP levels were observationally associated with calcium and body mass index (BMI),these associations were not supported by causal analyses. Despite well-powered sample sizes from consortia, there were no associations of rs2282679 with any other traits and diseases: fasting glucose (0.00 mmol/l [95% CI -0.01, 0.01]; p=1.00; n=46,186); fasting insulin (0.01 pmol/l [95% CI -0.00, 0.01,] ;p=0.22; n=46,186); BMI (0.00 kg/m(2) [95% CI -0.01, 0.01]; p=0.80; n=127,587); bone mineral density (0.01 g/cm(2) [95% CI -0.01, 0.03]; p=0.36; n=32,961); mean arterial pressure (-0.06 mm Hg [95% CI -0.19, 0.07]); p=0.36; n=28,775); ischemic stroke (odds ratio [OR] = 1.00 [95% CI 0.97, 1.04]; p=0.92; n=12, 389/62, 004 cases/controls); coronary artery disease (OR = 1.02 [95% CI 0.99, 1.05]; p=0.31; n=2,233/64, 762); or type 2 diabetes (OR = 1.01 [95% CI 0.97, 1.05]; p=0.76; n=9, 580/53, 810). Conclusions: DBP has no demonstrable causal effect on any of the diseases or traits investigated here, except 25OHD levels. It remains to be determined whether 25OHD has a causal effect on these outcomes independent of DBP
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