28 research outputs found
Beyond 2-D Mass-Radius Relationships: A Nonparametric and Probabilistic Framework for Characterizing Planetary Samples in Higher Dimensions
Fundamental to our understanding of planetary bulk compositions is the
relationship between their masses and radii, two properties that are often not
simultaneously known for most exoplanets. However, while many previous studies
have modeled the two-dimensional relationship between planetary mass and radii,
this approach largely ignores the dependencies on other properties that may
have influenced the formation and evolution of the planets. In this work, we
extend the existing nonparametric and probabilistic framework of \texttt{MRExo}
to jointly model distributions beyond two dimensions. Our updated framework can
now simultaneously model up to four observables, while also incorporating
asymmetric measurement uncertainties and upper limits in the data. We showcase
the potential of this multi-dimensional approach to three science cases: (i) a
4-dimensional joint fit to planetary mass, radius, insolation, and stellar
mass, hinting of changes in planetary bulk density across insolation and
stellar mass; (ii) a 3-dimensional fit to the California Kepler Survey sample
showing how the planet radius valley evolves across different stellar masses;
and (iii) a 2-dimensional fit to a sample of Class-II protoplanetary disks in
Lupus while incorporating the upper-limits in dust mass measurements. In
addition, we employ bootstrap and Monte-Carlo sampling to quantify the impact
of the finite sample size as well as measurement uncertainties on the predicted
quantities. We update our existing open-source user-friendly \texttt{MRExo}
\texttt{Python} package with these changes, which allows users to apply this
highly flexible framework to a variety of datasets beyond what we have shown
here.Comment: Accepted in ApJ. Updated MRExo package and sample scripts available
here: https://github.com/shbhuk/mrexo/tree/v1.0dev. Package will be released
on PyPI (pip) along with full documentation upon publication in Ap
Synthesis and Assembly of Nonspherical Hollow Silica Colloids Under Confinement
Hard peanut-shaped colloids were synthesized and organized into a degenerate crystal (DC), a phase previously observed only in simulations. In this structure, particle lobes tile a triangular lattice while their orientations uniformly populate the three underlying crystalline directions
Importance of Sample Selection in Exoplanet Atmosphere Population Studies
Understanding planet formation requires robust population studies, which are
designed to reveal trends in planet properties. In this work, we aim to
determine if different methods for selecting populations of exoplanets for
atmospheric characterization with JWST could influence population-level
inferences. We generate three hypothetical surveys of
super-Earths/sub-Neptunes, each spanning a similar radius-insolation flux
space. The survey samples are constructed based on three different selection
criteria (evenly-spaced-by-eye, binned, and a quantitative selection function).
Using an injection-recovery technique, we test how robustly individual-planet
atmospheric parameters and population-level parameters can be retrieved. We
find that all three survey designs result in equally suitable targets for
individual atmospheric characterization, but not equally suitable targets for
constraining population parameters. Only samples constructed with a
quantitative method or that are sufficiently evenly-spaced-by-eye result in
robust population parameter constraints. Furthermore, we find that the sample
with the best targets for individual atmospheric study does not necessarily
result in the best constrained population parameters. The method of sample
selection must be considered. We also find that there may be large variability
in population-level results with a sample that is small enough to fit in a
single JWST cycle (12 planets), suggesting that the most successful
population-level analyses will be multi-cycle. Lastly, we infer that our
exploration of sample selection is limited by the small number of transiting
planets with measured masses around bright stars. Our results can guide future
development of programs that aim to determine underlying trends in exoplanet
atmospheric properties and, by extension, formation and evolution processes.Comment: 16 pages, 7 figures, accepted Ap
Formation of Super-Earths
Super-Earths are the most abundant planets known to date and are
characterized by having sizes between that of Earth and Neptune, typical
orbital periods of less than 100 days and gaseous envelopes that are often
massive enough to significantly contribute to the planet's overall radius.
Furthermore, super-Earths regularly appear in tightly-packed multiple-planet
systems, but resonant configurations in such systems are rare. This chapters
summarizes current super-Earth formation theories. It starts from the formation
of rocky cores and subsequent accretion of gaseous envelopes. We follow the
thermal evolution of newly formed super-Earths and discuss their atmospheric
mass loss due to disk dispersal, photoevaporation, core-cooling and collisions.
We conclude with a comparison of observations and theoretical predictions,
highlighting that even super-Earths that appear as barren rocky cores today
likely formed with primordial hydrogen and helium envelopes and discuss some
paths forward for the future.Comment: Invited review accepted for publication in the 'Handbook of
Exoplanets,' Planet Formation section, Springer Reference Works, Juan Antonio
Belmonte and Hans Deeg, Ed
Planetary Candidates Observed by Kepler. VIII. A Fully Automated Catalog With Measured Completeness and Reliability Based on Data Release 25
We present the Kepler Object of Interest (KOI) catalog of transiting
exoplanets based on searching four years of Kepler time series photometry (Data
Release 25, Q1-Q17). The catalog contains 8054 KOIs of which 4034 are planet
candidates with periods between 0.25 and 632 days. Of these candidates, 219 are
new and include two in multi-planet systems (KOI-82.06 and KOI-2926.05), and
ten high-reliability, terrestrial-size, habitable zone candidates. This catalog
was created using a tool called the Robovetter which automatically vets the
DR25 Threshold Crossing Events (TCEs, Twicken et al. 2016). The Robovetter also
vetted simulated data sets and measured how well it was able to separate TCEs
caused by noise from those caused by low signal-to-noise transits. We discusses
the Robovetter and the metrics it uses to sort TCEs. For orbital periods less
than 100 days the Robovetter completeness (the fraction of simulated transits
that are determined to be planet candidates) across all observed stars is
greater than 85%. For the same period range, the catalog reliability (the
fraction of candidates that are not due to instrumental or stellar noise) is
greater than 98%. However, for low signal-to-noise candidates between 200 and
500 days around FGK dwarf stars, the Robovetter is 76.7% complete and the
catalog is 50.5% reliable. The KOI catalog, the transit fits and all of the
simulated data used to characterize this catalog are available at the NASA
Exoplanet Archive.Comment: 61 pages, 23 Figures, 9 Tables, Accepted to The Astrophysical Journal
Supplement Serie
Children’s and adolescents’ rising animal-source food intakes in 1990–2018 were impacted by age, region, parental education and urbanicity
Animal-source foods (ASF) provide nutrition for children and adolescents’ physical and cognitive development. Here, we use data from the Global Dietary Database and Bayesian hierarchical models to quantify global, regional and national ASF intakes between 1990 and 2018 by age group across 185 countries, representing 93% of the world’s child population. Mean ASF intake was 1.9 servings per day, representing 16% of children consuming at least three daily servings. Intake was similar between boys and girls, but higher among urban children with educated parents. Consumption varied by age from 0.6 at <1 year to 2.5 servings per day at 15–19 years. Between 1990 and 2018, mean ASF intake increased by 0.5 servings per week, with increases in all regions except sub-Saharan Africa. In 2018, total ASF consumption was highest in Russia, Brazil, Mexico and Turkey, and lowest in Uganda, India, Kenya and Bangladesh. These findings can inform policy to address malnutrition through targeted ASF consumption programmes.publishedVersio
Incident type 2 diabetes attributable to suboptimal diet in 184 countries
The global burden of diet-attributable type 2 diabetes (T2D) is not well established. This risk assessment model estimated T2D incidence among adults attributable to direct and body weight-mediated effects of 11 dietary factors in 184 countries in 1990 and 2018. In 2018, suboptimal intake of these dietary factors was estimated to be attributable to 14.1 million (95% uncertainty interval (UI), 13.8–14.4 million) incident T2D cases, representing 70.3% (68.8–71.8%) of new cases globally. Largest T2D burdens were attributable to insufficient whole-grain intake (26.1% (25.0–27.1%)), excess refined rice and wheat intake (24.6% (22.3–27.2%)) and excess processed meat intake (20.3% (18.3–23.5%)). Across regions, highest proportional burdens were in central and eastern Europe and central Asia (85.6% (83.4–87.7%)) and Latin America and the Caribbean (81.8% (80.1–83.4%)); and lowest proportional burdens were in South Asia (55.4% (52.1–60.7%)). Proportions of diet-attributable T2D were generally larger in men than in women and were inversely correlated with age. Diet-attributable T2D was generally larger among urban versus rural residents and higher versus lower educated individuals, except in high-income countries, central and eastern Europe and central Asia, where burdens were larger in rural residents and in lower educated individuals. Compared with 1990, global diet-attributable T2D increased by 2.6 absolute percentage points (8.6 million more cases) in 2018, with variation in these trends by world region and dietary factor. These findings inform nutritional priorities and clinical and public health planning to improve dietary quality and reduce T2D globally.publishedVersio
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Variations in accelerometry measured physical activity and sedentary time across Europe – harmonized analyses of 47,497 children and adolescents
Funder: Ministero delle Politiche Agricole Alimentari e Forestali; doi: http://dx.doi.org/10.13039/501100005401Funder: ZonMw; doi: http://dx.doi.org/10.13039/501100001826Funder: The Research Council of Norway, Division for Society and Health.Abstract: Background: Levels of physical activity and variation in physical activity and sedentary time by place and person in European children and adolescents are largely unknown. The objective of the study was to assess the variations in objectively measured physical activity and sedentary time in children and adolescents across Europe. Methods: Six databases were systematically searched to identify pan-European and national data sets on physical activity and sedentary time assessed by the same accelerometer in children (2 to 9.9 years) and adolescents (≥10 to 18 years). We harmonized individual-level data by reprocessing hip-worn raw accelerometer data files from 30 different studies conducted between 1997 and 2014, representing 47,497 individuals (2–18 years) from 18 different European countries. Results: Overall, a maximum of 29% (95% CI: 25, 33) of children and 29% (95% CI: 25, 32) of adolescents were categorized as sufficiently physically active. We observed substantial country- and region-specific differences in physical activity and sedentary time, with lower physical activity levels and prevalence estimates in Southern European countries. Boys were more active and less sedentary in all age-categories. The onset of age-related lowering or leveling-off of physical activity and increase in sedentary time seems to become apparent at around 6 to 7 years of age. Conclusions: Two third of European children and adolescents are not sufficiently active. Our findings suggest substantial gender-, country- and region-specific differences in physical activity. These results should encourage policymakers, governments, and local and national stakeholders to take action to facilitate an increase in the physical activity levels of young people across Europe