ABSTRACT
The composition of rocky exoplanets in the context of stars’ composition provides important constraints to formation theories. In this study, we select a sample of exoplanets with mass and ...radius measurements with an uncertainty $\lt 25{{\ \rm per\ cent}}$ and obtain their interior structure. We calculate compositional markers, ratios of iron to magnesium and silicon, as well as core mass fractions (CMFs) that fit the planetary parameters, and compare them to the stars. We find four key results that successful planet formation theories need to predict: (1) In a population sense, the composition of rocky planets spans a wider range than stars. The stars’ Fe/Si distribution is close to a Gaussian distribution $1.63^{+0.91}_{-0.85}$, while the planets’ distribution peaks at lower values and has a longer tail, $1.15^{+1.43}_{-0.76}$. It is easier to see the discrepancy in CMF space, where primordial stellar composition is $0.32^{+0.14}_{-0.12}$, while rocky planets follow a broader distribution $0.24^{+0.33}_{-0.18}$. (2) We introduce uncompressed density ($\overline{\rho _0}$ at reference pressure/temperature) as a metric to compare compositions. With this, we find what seems to be the maximum iron enrichment that rocky planets attain during formation ($\overline{\rho _0}\sim 6$ and CMF ∼0.8). (3) Highly irradiated planets exhibit a large range of compositions. If these planets are the result of atmospheric evaporation, iron enrichment and perhaps depletion must happen before gas dispersal. And, (4) We identify a group of highly irradiated planets that, if rocky, would be twofold depleted in Fe/Si with respect to the stars. Without a reliable theory for forming iron-depleted planets, these are interesting targets for follow-up.
This paper employs the concepts of sustainability and habitability to define and measure ecological urbanism in informal settlements founded by people who have been forcibly displaced by violence. ...The objective is to identify the obstacles in meeting the tenets of ecological urbanism in informal settlements. We offer primary research from La Primavera, an informal settlement founded by internally displaced people in the late 1970s, located in the corregimiento El Hatillo of Barbosa, Antioquia in northwestern Colombia. Primary research includes qualitative and quantitative data gathered through 72 surveys and 45 technical assessments of properties and houses in the settlement. Situated between the Aburrá River and the northbound highway, above a gas pipeline and under an electricity pylon, La Primavera exists in a state of extreme risk, exacerbated by increasing migration which threatens to exceed the carrying capacity of the territory. Moreover, in Article 35 of Law 388 of 1997, the territory was declared a protected or restricted area and earmarked for the development of the regional commuter train, called the Tren de Cercanías, in 2017. The case study highlights the contradictions in the development agenda in Colombia by showing how development projects designed for the economic betterment and environmental conservation of the region negatively impact the quality of life for the most vulnerable inhabitants and expose them to greater environmental, economic, and social risk.
High throughput phenotyping (HTP) platforms and devices are increasingly used for the characterization of growth and developmental processes for large sets of plant genotypes. Such HTP data require ...challenging statistical analyses in which longitudinal genetic signals need to be estimated against a background of spatio-temporal noise processes. We propose a two-stage approach for the analysis of such longitudinal HTP data. In a first stage, we correct for design features and spatial trends per time point. In a second stage, we focus on the longitudinal modelling of the spatially corrected data, thereby taking advantage of shared longitudinal features between genotypes and plants within genotypes. We propose a flexible hierarchical three-level P-spline growth curve model, with plants/plots nested in genotypes, and genotypes nested in populations. For selection of genotypes in a plant breeding context, we show how to extract new phenotypes, like growth rates, from the estimated genotypic growth curves and their first-order derivatives. We illustrate our approach on HTP data from the PhenoArch greenhouse platform at INRAE Montpellier and the outdoor Field Phenotyping platform at ETH Zürich.
Abstract Mercury is notoriously difficult to form in Solar System simulations, due to its small mass and iron-rich composition. Smooth particle hydrodynamics simulations of collisions have found that ...a Mercury-like body could be formed by one or multiple giant impacts, but due to the chaotic nature of collisions, it is difficult to create a scenario where such impacts will take place. Recent work has found more success forming Mercury analogues by adding additional embryos near Mercury’s orbit. In this work, we aim to form Mercury by simulating the formation of the Solar System in the presence of the giant planets Jupiter and Saturn. We test out the effect of an inner disk of embryos added on to the commonly used narrow annulus of initial material. We form Mercury analogues with core-mass fractions (CMFs) > 0.4 in ∼10% of our simulations, and twice that number of Mercury analogues form during the formation process but are unstable and do not last to the end of the simulations. Mercury analogues form at similar rates for both disks with and without an inner component, and most of our Mercury analogues have lower CMFs than that of Mercury, ∼0.7, due to significant accretion of debris material. We suggest that a more in-depth understanding of the fraction of debris mass that is lost to collisional grinding is necessary to understand Mercury’s formation, or some additional mechanism is required to stop this debris from accreting.
Community-based disaster management (CBDM) has replaced traditional models of disaster risk reduction (DRR), giving the community a more participatory role in the planning and implementation of risk ...mitigation and preparedness strategies, disaster response, and post-disaster recovery measures. This shift in disaster response approaches has impacted understandings of vulnerability and resilience, leading scholars and policy makers to move away from a physical definition of vulnerability and to incorporate social variables. However, in Colombia, a traditional DRR approach still prevails. The National Risk Management Policy employs a top-down approach to risk reduction and disaster management, relying on the action of governmental authorities without community participation in the design or implementation of risk management planning and strategy. This article reveals the deficiencies of traditional DRR approaches. The Colombian government’s post-disaster resettlement project after a 2015 landslide in Salgar, Antioquia that resulted in 98 people dead or missing did not contribute to the reduction of vulnerability for the resettled community. To accurately measure post-disaster vulnerability and resilience, a new holistic model of indicators that includes both social and biophysical variables that illustrate and measure the relevance of preexisting vulnerabilities was developed. Local data was collected through 178 surveys administered to the inhabitants of Salgar’s three post-disaster resettlement sectors—La Habana, La Florida, and Las Margaritas—to construct an accurate picture of the populations affected by the disaster. Our results show that in the case of Salgar, social vulnerabilities persist even in the physical components of the resettlement sites where new infrastructure would be expected to reduce hazardous conditions and exposure to risk.
ABSTRACT
Recent observations of rocky super-Earths have revealed an apparent wider distribution of Fe/Mg ratios, or core to mantle ratios, than the planets in our Solar system. This study aims to ...understand how much of the chemical diversity in the super-Earth population can arise from giant impacts during planetary formation. Planet formation simulations have only recently begun to treat collisions more realistically in an attempt to replicate the planets in our Solar system. We investigate planet formation more generally by simulating the formation of rocky super-Earths with varying initial conditions using a version of symba, a gravitational N-body code, that incorporates realistic collisions. We track the maximum plausible change in composition after each impact. The final planets span a range of Fe/Mg ratios similar to the Solar system planets, but do not completely match the distribution in super-Earth data. We only form a few planets with minor iron-depletion, suggesting other mechanisms are at work. The most iron-rich planets have a lower Fe/Mg ratio than Mercury, and are less enriched than planets such as Kepler-100b. This indicates that further work on our understanding of planet formation and further improvement of precision of mass and radius measurements are required to explain planets at the extremes of this Fe/Mg distribution.
GJ 1214b stands out among the detected low-mass exoplanets, because it is, so far, the only one amenable to transmission spectroscopy. Up to date there is no consensus about the composition of its ...envelope although most studies suggest a high molecular weight atmosphere. In particular, it is unclear if hydrogen and helium are present or if the atmosphere is water dominated. Here, we present results on the composition of the envelope obtained by using an internal structure and evolutionary model to fit the mass and radius data. By examining all possible mixtures of water and H/He, with the corresponding opacities, we find that the bulk amount of H/He of GJ 1214b is at most 7% by mass. In general, we find the radius of warm sub-Neptunes to be most sensitive to the amount of H/He. We note that all (Kepler-11b,c,d,f, Kepler-18b, Kepler-20b, 55Cnc-e, Kepler-36c, and Kepler-68b) but two (Kepler-11e and Kepler-30b) of the discovered low-mass planets so far have less than 10% H/He. In fact, Kepler-11e and Kepler-30b have 10%-18% and 5%-15% bulk H/He. Conversely, little can be determined about the H sub(2)O or rocky content of sub-Neptune planets. We find that although a 100% water composition fits the data for GJ 1214b, based on formation constraints the presence of heavier refractory material on this planet is expected, and hence, so is a component lighter than water required. The same is true for Kepler-11f. A robust determination by transmission spectroscopy of the composition of the upper atmosphere of GJ 1214b will help determine the extent of compositional segregation between the atmosphere and the envelope.
The stability of Earth's climate on geological timescales is enabled by the carbon-silicate cycle that acts as a negative feedback mechanism stabilizing surface temperatures via the intake and ...outgassing of atmospheric carbon. On Earth, this thermostat is enabled by plate tectonics that sequesters outgassed CO2 back into the mantle via weathering and subduction at convergent margins. Here we propose a separate tectonic mechanism-vertical recycling-that can serve as the vehicle for CO2 outgassing and sequestration over long timescales. The mechanism requires continuous tidal heating, which makes it particularly relevant to planets in the habitable zone of M stars. Dynamical models of this vertical recycling scenario and stability analysis show that temperate climates stable over timescales of billions of years are realized for a variety of initial conditions, even as the M star dims over time. The magnitude of equilibrium surface temperatures depends on the interplay of sea weathering and outgassing, which in turn depends on planetary carbon content, so that planets with lower carbon budgets are favored for temperate conditions. The habitability of planets such as found in the Trappist-1 system may be rooted in tidally driven tectonics.
Parasites release extracellular vesicles (EVs) which, in some cases, modulate the host's immune response contributing to the establishment of the infection. In this work we have isolated and ...characterized the EVs released by trophozoites of the human protozoan parasite
, the causal agent of amoebiasis, when alone or in coculture with human neutrophils, and determined their effect on neutrophil NETs and ROS production. Nanoparticle tracking analysis showed that amoebic EVs are variable in size, ranging from less than 50 nm to nearly 600 nm in diameter (average of 167 nm), whereas neutrophil EVs are more uniform in size, with an average of 136 nm. In cocultures amoeba:neutrophil (1:100) most EVs are 98 nm in size, which is the typical size of exosomes. EVs from amoebae and neutrophils showed almost equal levels of ROS, which were considerably increased in EVs from cocultures. Uptake of amoebic EVs by neutrophils was demonstrated by fluorescence and resulted in a significant reduction in the oxidative burst and NET release triggered by PMA, ionophore A23187, or the amoebae itself used as stimuli. Interestingly, uptake of EVs from cocultures did not affect ROS production, but instead caused a greater delay in the onset of NETs release and in their quantity. A comparative proteomic analysis between the EVs of amoebae and neutrophils separately vs the cocultures showed a similar distribution of protein categories in the GO analysis, but differences in the expression and abundance of proteins such as the N-acetyl-D-galactosamine (GalNAc) inhibitable surface lectin and calreticulin in amoeba EVs, and various antimicrobial molecules in neutrophil EVs, such as lactoferrin and myeloperoxidase. These results highlight the importance of EVs in the immunomodulatory effects exerted by amoeba on human neutrophils.
Planetary-scale collisions are common during the last stages of formation of solid planets, including the solar system terrestrial planets. The problem of growing planets has been divided into ...studying the gravitational interaction of embryos relevant on million year timescales and treated with N-body codes and the collision between objects with a timescale of hours to days and treated with smoothed-particle hydrodynamics. These are now being coupled with simple parameterized models. We set out to investigate if machine-learning techniques can offer a better solution by predicting the outcome of collisions that can then be used in N-body simulations. We considered three different supervised machine-learning approaches: gradient boosting regression trees, nested models, and Gaussian processes (GPs). We found that the former produced the best results, and that it was slightly surpassed by ensembling different algorithms. With GPs, we found the regions of parameter space that may yield the most information to machine-learning algorithms. Thus, we suggest new smoothed-particle hydrodynamics calculations to focus first on mass ratios 0.5.
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