Young exoplanets are snapshots of the planetary evolution process. Planets that orbit stars in young associations are particularly important because the age of the planetary system is well ...constrained. We present the discovery of a transiting planet larger than Neptune but smaller than Saturn in the 45 Myr Tucana-Horologium young moving group. The host star is a visual binary, and our follow-up observations demonstrate that the planet orbits the G6V primary component, DS Tuc A (HD 222259A, TIC 410214986). We first identified transits using photometry from the Transiting Exoplanet Survey Satellite (TESS; alerted as TOI 200.01). We validated the planet and improved the stellar parameters using a suite of new and archival data, including spectra from Southern Astrophysical Research/Goodman, South African Extremely Large Telescope/High Resolution Spectrograph and Las Cumbres Observatories/Network of Robotic Echelle Spectrographs; transit photometry from Spitzer; and deep adaptive optics imaging from Gemini/Gemini Planet Imager. No additional stellar or planetary signals are seen in the data. We measured the planetary parameters by simultaneously modeling the photometry with a transit model and a Gaussian process to account for stellar variability. We determined that the planetary radius is 5.70 0.17 R⊕ and that the orbital period is 8.1 days. The inclination angles of the host star's spin axis, the planet's orbital axis, and the visual binary's orbital axis are aligned within 15° to within the uncertainties of the relevant data. DS Tuc Ab is bright enough (V = 8.5) for detailed characterization using radial velocities and transmission spectroscopy.
Abstract
Large Igneous Province eruptions coincide with many major Phanerozoic mass extinctions, suggesting a cause-effect relationship where volcanic degassing triggers global climatic changes. In ...order to fully understand this relationship, it is necessary to constrain the quantity and type of degassed magmatic volatiles, and to determine the depth of their source and the timing of eruption. Here we present direct evidence of abundant CO
2
in basaltic rocks from the end-Triassic Central Atlantic Magmatic Province (CAMP), through investigation of gas exsolution bubbles preserved by melt inclusions. Our results indicate abundance of CO
2
and a mantle and/or lower-middle crustal origin for at least part of the degassed carbon. The presence of deep carbon is a key control on the emplacement mode of CAMP magmas, favouring rapid eruption pulses (a few centuries each). Our estimates suggest that the amount of CO
2
that each CAMP magmatic pulse injected into the end-Triassic atmosphere is comparable to the amount of anthropogenic emissions projected for the 21
st
century. Such large volumes of volcanic CO
2
likely contributed to end-Triassic global warming and ocean acidification.
Records suggest that the Permo-Triassic mass extinction (PTME) involved one of the most severe terrestrial ecosystem collapses of the Phanerozoic. However, it has proved difficult to constrain the ...extent of the primary productivity loss on land, hindering our understanding of the effects on global biogeochemistry. We build a new biogeochemical model that couples the global Hg and C cycles to evaluate the distinct terrestrial contribution to atmosphere-ocean biogeochemistry separated from coeval volcanic fluxes. We show that the large short-lived Hg spike, and nadirs in δ
Hg and δ
C values at the marine PTME are best explained by a sudden, massive pulse of terrestrial biomass oxidation, while volcanism remains an adequate explanation for the longer-term geochemical changes. Our modelling shows that a massive collapse of terrestrial ecosystems linked to volcanism-driven environmental change triggered significant biogeochemical changes, and cascaded organic matter, nutrients, Hg and other organically-bound species into the marine system.
Vitamin D was used to treat tuberculosis (TB) in the preantibiotic era. Prospective studies to evaluate the effect of vitamin D supplementation on antimycobacterial immunity have not previously been ...performed.
To determine the effect of vitamin D supplementation on antimycobacterial immunity and vitamin D status.
A double-blind randomized controlled trial was conducted in 192 healthy adult TB contacts in London, United Kingdom. Participants were randomized to receive a single oral dose of 2.5 mg vitamin D or placebo and followed up at 6 weeks.
The primary outcome measure was assessed with a functional whole blood assay (BCG-lux assay), which measures the ability of whole blood to restrict luminescence, and thus growth, of recombinant reporter mycobacteria in vitro; the readout is expressed as a luminescence ratio (luminescence postinfection/baseline luminescence). IFN-gamma responses to the Mycobacterium tuberculosis antigens early secretory antigenic target-6 and culture filtrate protein 10 were determined with a second whole blood assay. Vitamin D supplementation significantly enhanced the ability of participants' whole blood to restrict BCG-lux luminescence in vitro compared with placebo (mean luminescence ratio at follow-up, 0.57, vs. 0.71, respectively; 95% confidence interval for difference, 0.01-0.25; p=0.03) but did not affect antigen-stimulated IFN-gamma secretion.
A single oral dose of 2.5 mg vitamin D significantly enhanced the ability of participants' whole blood to restrict BCG-lux luminescence in vitro without affecting antigen-stimulated IFN-gamma responses. Clinical trials should be performed to determine whether vitamin D supplementation prevents reactivation of latent TB infection. Clinical trial registered with www.clinicaltrials.gov (NCT 00157066).
The rise of oxygen on the early Earth (about 2.4 billion years ago) caused a reorganization of marine nutrient cycles, including that of nitrogen, which is important for controlling global primary ...productivity. However, current geochemical records lack the temporal resolution to address the nature and timing of the biogeochemical response to oxygenation directly. Here we couple records of ocean redox chemistry with nitrogen isotope (
N/
N) values from approximately 2.31-billion-year-old shales of the Rooihoogte and Timeball Hill formations in South Africa, deposited during the early stages of the first rise in atmospheric oxygen on the Earth (the Great Oxidation Event). Our data fill a gap of about 400 million years in the temporal
N/
N record and provide evidence for the emergence of a pervasive aerobic marine nitrogen cycle. The interpretation of our nitrogen isotope data in the context of iron speciation and carbon isotope data suggests biogeochemical cycling across a dynamic redox boundary, with primary productivity fuelled by chemoautotrophic production and a nitrogen cycle dominated by nitrogen loss processes using newly available marine oxidants. This chemostratigraphic trend constrains the onset of widespread nitrate availability associated with ocean oxygenation. The rise of marine nitrate could have allowed for the rapid diversification and proliferation of nitrate-using cyanobacteria and, potentially, eukaryotic phytoplankton.
We have simulated the formation of a galaxy cluster in a Λ cold dark matter universe using 13 different codes modelling only gravity and non-radiative hydrodynamics (ramses, ART, arepo, hydra and ...nine incarnations of gadget). This range of codes includes particle-based, moving and fixed mesh codes as well as both Eulerian and Lagrangian fluid schemes. The various gadget implementations span classic and modern smoothed particle hydrodynamics (SPH) schemes. The goal of this comparison is to assess the reliability of cosmological hydrodynamical simulations of clusters in the simplest astrophysically relevant case, that in which the gas is assumed to be non-radiative. We compare images of the cluster at z = 0, global properties such as mass and radial profiles of various dynamical and thermodynamical quantities. The underlying gravitational framework can be aligned very accurately for all the codes allowing a detailed investigation of the differences that develop due to the various gas physics implementations employed. As expected, the mesh-based codes ramses, art and arepo form extended entropy cores in the gas with rising central gas temperatures. Those codes employing classic SPH schemes show falling entropy profiles all the way into the very centre with correspondingly rising density profiles and central temperature inversions. We show that methods with modern SPH schemes that allow entropy mixing span the range between these two extremes and the latest SPH variants produce gas entropy profiles that are essentially indistinguishable from those obtained with grid-based methods.
The Carnian Pluvial Episode (Late Triassic) was a time of global environmental changes and possibly substantial coeval volcanism. The extent of the biological turnover in marine and terrestrial ...ecosystems is not well understood. Here, we present a meta-analysis of fossil data that suggests a substantial reduction in generic and species richness and the disappearance of 33% of marine genera. This crisis triggered major radiations. In the sea, the rise of the first scleractinian reefs and rock-forming calcareous nannofossils points to substantial changes in ocean chemistry. On land, there were major diversifications and originations of conifers, insects, dinosaurs, crocodiles, lizards, turtles, and mammals. Although there is uncertainty on the precise age of some of the recorded biological changes, these observations indicate that the Carnian Pluvial Episode was linked to a major extinction event and might have been the trigger of the spectacular radiation of many key groups that dominate modern ecosystems.
Stable isotope ratios of sulfur (
δ
34S) and oxygen (
δ
18O) in marine sulfate respond to changes in fluxes and processes in the global sulfur cycle. The two isotope systems respond on different time ...scales to different factors affecting the global sulfur cycle. Sulfur isotopes respond primarily to the relative fluxes of weathering-derived sulfate to the oceans versus the net flux of sulfur exported from the oceans as pyrite in marine sediments. At the present day, this response is relatively slow (∼
20 Ma) because of the large size of the marine sulfate reservoir; ancient oceans had lower sulfate concentrations and thus sulfate residence times may have been shorter. The
δ
34S of marine sulfate is also sensitive to the development of a significant reservoir of H
2S in ancient stratified oceans. Sulfate–oxygen isotopes respond primarily to changes in the cycling of sulfur in the oceans and marine sediments. Sulfur disproportionation, oxic and anaerobic sulfide oxidation all impart different
δ
18O signatures to marine sulfate; the relative importance of these different processes is in turn controlled by the distribution of redox conditions and microbial ecology of sea-floor sediments. The mutual interpretation of changes in marine sulfate
δ
34S and
δ
18O can thus give rather precise information on the nature of changes in global sulfur cycling. Recently, records of isotope compositions of ancient marine sulfate have become available through the analysis of carbonate-associated sulfate (CAS) in limestones and marine biogenic barite, both of which provide far more continuous records than previous data based primarily on marine evaporite sulfate minerals.
We review a number of case studies which use sulfur or combined sulfur and oxygen isotopic records derived from CAS and biogenic barite. Proterozoic CAS-sulfur isotope datasets often show marked variations over very small stratigraphic intervals (e.g. 20‰ over 300 m). When examined in conjunction with estimates of deposition rates, they are used to infer a new evolutionary curve of marine sulfate concentrations and therefore a protracted oxidation of the Earth's biosphere. Through the Cretaceous–Tertiary interval, the marine sulfate–sulfur record is characterised by significant periods of relative stability punctuated by phases of more rapid change (limited to 7‰ variation over the last 130 Ma). The Carboniferous was characterized essentially by a gradual change of 9‰ over 60 Ma. By contrast, at the Permian–Triassic boundary, extreme changes occur over very short geological time scales (14‰ over <
1 Ma); simple mass balance considerations suggest the development of a large, relatively short-lived, reservoir of H
2S in the oceanic water column at this time. In this case, it is the short time scale of the response of the sulfate–oxygen record that enables the interpretation of rapid changes in oceanic redox state. Over the last 10 Ma, sulfate–oxygen
δ
18O in biogenic barite exhibits large isotope changes (∼
7‰) that occur independently of those in sulfate–sulfur. These changes must reflect changes in depositional/redox environment at the ocean margins and/or changes in microbial cycling of sulfur, but the exact cause remains controversial. Our limited understanding of the influence of redox environment and sediment microbial ecology on sulfur cycling currently restricts the level to which we are able to interpret such changes in marine sulfate
δ
18O.
Neutrophils contain antimicrobial peptides with antituberculous activity, but their contribution to immune resistance to tuberculosis (TB) infection has not been previously investigated to our ...knowledge. We determined differential white cell counts in peripheral blood of 189 adults who had come into contact with patients diagnosed with active TB in London, United Kingdom, and evaluated them for evidence of TB infection and capacity to restrict mycobacterial growth in whole-blood assays. Risk of TB infection was inversely and independently associated with peripheral blood neutrophil count in contacts of patients diagnosed with pulmonary TB. The ability of whole blood to restrict growth of Mycobacterium bovis bacille Calmette Guérin and Mycobacterium tuberculosis was impaired 7.3- and 3.1-fold, respectively, by neutrophil depletion. In microbiological media, human neutrophil peptides (HNPs) 1-3 killed M. tuberculosis. The neutrophil peptides cathelicidin LL-37 and lipocalin 2 restricted growth of the organism, the latter in an iron-dependent manner. Black African participants had lower neutrophil counts and lower circulating concentrations of HNP1-3 and lipocalin 2 than south Asian and white participants. Neutrophils contribute substantially to innate resistance to TB infection, an activity associated with their antimicrobial peptides. Elucidation of the regulation of neutrophil antimicrobial peptides could facilitate prevention and treatment of TB.
To report a case that substantiates the presence of hypoglycemia at the time of death of a young man with type 1 diabetes, who was found unresponsive in his undisturbed bed in the morning.
We ...describe a 23-year-old man with a history of type 1 diabetes treated with an insulin pump, who had recurrent severe hypoglycemia. In an effort to understand these episodes better and attempt to eliminate them, a retrospective (non-real-time) continuous subcutaneous glucose monitoring system (CGMS) was attached to the patient. He was found dead in his undisturbed bed 20 hours later. The insulin pump and CGMS were both downloaded for postmortem study.
Postmortem download of the data in the CGMS demonstrated glucose levels below 30 mg/dL around the time of his death, with only a minimal counter-regulatory response. This finding corresponded to a postmortem vitreous humor glucose of 25 mg/dL. An autopsy showed no major anatomic abnormalities that could have contributed to his death.
To our knowledge, this is the first documentation of hypoglycemia at the time of death in a patient with the "dead-in-bed" syndrome. This report should raise the awareness of physicians to the potentially lethal effects of hypoglycemia and provide justification for efforts directed at avoiding nocturnal hypoglycemia.
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