Nearly a century ago it was recognized that radiation absorption by stellar matter controls the internal temperature profiles within stars. Laboratory opacity measurements, however, have never been ...performed at stellar interior conditions, introducing uncertainties in stellar models. A particular problem arose when refined photosphere spectral analysis led to reductions of 30-50 per cent in the inferred amounts of carbon, nitrogen and oxygen in the Sun. Standard solar models using the revised element abundances disagree with helioseismic observations that determine the internal solar structure using acoustic oscillations. This could be resolved if the true mean opacity for the solar interior matter were roughly 15 per cent higher than predicted, because increased opacity compensates for the decreased element abundances. Iron accounts for a quarter of the total opacity at the solar radiation/convection zone boundary. Here we report measurements of wavelength-resolved iron opacity at electron temperatures of 1.9-2.3 million kelvin and electron densities of (0.7-4.0) × 10(22) per cubic centimetre, conditions very similar to those in the solar region that affects the discrepancy the most: the radiation/convection zone boundary. The measured wavelength-dependent opacity is 30-400 per cent higher than predicted. This represents roughly half the change in the mean opacity needed to resolve the solar discrepancy, even though iron is only one of many elements that contribute to opacity.
The first systematic study of opacity dependence on atomic number at stellar interior temperatures is used to evaluate discrepancies between measured and modeled iron opacity J. E. Bailey et al., ...Nature (London) 517, 56 (2015)NATUAS0028-083610.1038/nature14048. High-temperature (>180 eV) chromium and nickel opacities are measured with ±6%-10% uncertainty, using the same methods employed in the previous iron experiments. The 10%-20% experiment reproducibility demonstrates experiment reliability. The overall model-data disagreements are smaller than for iron. However, the systematic study reveals shortcomings in models for density effects, excited states, and open L-shell configurations. The 30%-45% underestimate in the modeled quasicontinuum opacity at short wavelengths was observed only from iron and only at temperature above 180 eV. Thus, either opacity theories are missing physics that has nonmonotonic dependence on the number of bound electrons or there is an experimental flaw unique to the iron measurement at temperatures above 180 eV.
We report a time-calibrated stratigraphic section in Colorado that contains unusually complete fossils of mammals, reptiles, and plants and elucidates the drivers and tempo of biotic recovery during ...the poorly known first million years after the Cretaceous-Paleogene mass extinction (KPgE). Within ~100 thousand years (ka) post-KPgE, mammalian taxonomic richness doubled, and maximum mammalian body mass increased to near pre-KPgE levels. A threefold increase in maximum mammalian body mass and dietary niche specialization occurred at ~300 ka post-KPgE, concomitant with increased megafloral standing species richness. The appearance of additional large mammals occurred by ~700 ka post-KPgE, coincident with the first appearance of Leguminosae (the bean family). These concurrent plant and mammal originations and body-mass shifts coincide with warming intervals, suggesting that climate influenced post-KPgE biotic recovery.
Climate-driven changes in biotic interactions can profoundly alter ecological communities, particularly when they impact foundation species. In marine systems, changes in herbivory and the consequent ...loss of dominant habitat forming species can result in dramatic community phase shifts, such as from coral to macroalgal dominance when tropical fish herbivory decreases, and from algal forests to ‘barrens’ when temperate urchin grazing increases. Here, we propose a novel phase-shift away from macroalgal dominance caused by tropical herbivores extending their range into temperate regions. We argue that this phase shift is facilitated by poleward-flowing boundary currents that are creating ocean warming hotspots around the globe, enabling the range expansion of tropical species and increasing their grazing rates in temperate areas. Overgrazing of temperate macroalgae by tropical herbivorous fishes has already occurred in Japan and the Mediterranean. Emerging evidence suggests similar phenomena are occurring in other temperate regions, with increasing occurrence of tropical fishes on temperate reefs.
In animal models, prenatal zinc deficiency induced epigenetic changes in the fetus, but data in humans are lacking. We aimed to examine associations between maternal zinc levels during pregnancy and ...DNA methylation in LINE-1 and Alu repetitive sequences in young adult offspring, as well as anthropometry and cardiometabolic parameters.
Participants were 74 pregnant women from the Chiang Mai Low Birth Weight cohort, and their offspring followed up at 20 years of age. Maternal plasma zinc concentrations were measured at approximately 36 weeks of gestation. DNA methylation levels in LINE-1 and Alu repetitive sequences were measured in the offspring, as well as anthropometry and cardiometabolic parameters (lipid profile, blood pressure, and glucose metabolism).
Over half of mothers (39/74; 53%) were zinc deficient (<50 μg/dL) during their third trimester of pregnancy. Maternal zinc concentrations during pregnancy were associated with LINE-1 DNA methylation levels in adult offspring. Specifically, lower prenatal zinc concentrations were associated with: 1) lower levels of total LINE-1 methylation; 2) lower levels of LINE-1 hypermethylation loci; and 3) higher levels of LINE-1 partial methylation loci. Prenatal zinc concentrations were not associated with Alu methylation levels, nor with any anthropometric or cardiometabolic parameters in adult offspring. However, we observed associations between Alu and LINE-1 methylation patterns and cardiometabolic outcomes in offspring, namely total cholesterol levels and diastolic blood pressure, respectively.
Lower maternal zinc concentrations late in gestation were associated with changes in DNA methylation in later life. Thus, zinc deficiency during pregnancy may induce alterations in total LINE-1 methylation and LINE-1 hypermethylation loci. These results suggest a possible epigenetic link between zinc deficiency during pregnancy and long-term outcomes in the offspring.
We compare Hubble Space Telescope observations of Jupiter's FUV auroras with contemporaneous conjugate Juno in situ observations in the equatorial middle magnetosphere of Jupiter. We show that bright ...patches on and equatorward of the main emission are associated with hot plasma injections driven by ongoing active magnetospheric convection. During the interval that Juno crossed the magnetic field lines threading the complex of auroral patches, a series of energetic particle injection signatures were observed, and immediately prior, the plasma data exhibited flux tube interchange events indicating ongoing convection. This presents the first direct evidence that auroral morphology previously termed “strong injections” is indeed a manifestation of magnetospheric injections, and that this morphology indicates that Jupiter's magnetosphere is undergoing an interval of active iogenic plasma outflow.
Plain Language Summary
Auroras, known as the “Northern (or Southern) Lights” on Earth, are spectacular manifestations of energetic processes occurring in the space environment of a planet. The behavior of Jupiter's magnetosphere is dominated by the planet's rapid rotation, along with the centrifugally‐driven outflow of plasma (ionized gas) originating from active volcanoes on the moon Io. A prominent auroral feature on Jupiter has for many years been interpreted as a sign that Jupiter's magnetosphere is undergoing active convection, in which plasma from Io “falls” away from the planet, to be replaced by hot, relatively empty “bubbles” known as injections, moving inward. This feature comprises prominent patches of bright emission that are often observed in Jupiter's auroras, though the evidence associating them with injections has been largely circumstantial. Here we show that the NASA Juno spacecraft flew through such injections in the equatorial magnetosphere on magnetic field lines mapping to a cluster of auroral patches as observed by HST. The Juno data also indicated the interval was characterized by signatures of convection and outflow of plasma originating from Io. This demonstrates that auroral patches are signatures of injections, and that auroral emissions are an important tool for diagnosing the behavior of planetary magnetospheres.
Key Points
Bright FUV auroral patches on Jupiter are associated with magnetospheric injections and magnetospheric convection
Hubble Space Telescope and Juno equatorial data show a cluster of patches is magnetically conjugate with energetic particle injections
The interval also exhibits flux tube interchange and lagging magnetic field associated with plasma mass outflow
Summary
Respirable aerosols (< 5 µm in diameter) present a high risk of SARS‐CoV‐2 transmission. Guidelines recommend using aerosol precautions during aerosol‐generating procedures, and droplet (> ...5 µm) precautions at other times. However, emerging evidence indicates respiratory activities may be a more important source of aerosols than clinical procedures such as tracheal intubation. We aimed to measure the size, total number and volume of all human aerosols exhaled during respiratory activities and therapies. We used a novel chamber with an optical particle counter sampling at 100 l.min‐1 to count and size‐fractionate close to all exhaled particles (0.5–25 µm). We compared emissions from ten healthy subjects during six respiratory activities (quiet breathing; talking; shouting; forced expiratory manoeuvres; exercise; and coughing) with three respiratory therapies (high‐flow nasal oxygen and single or dual circuit non‐invasive positive pressure ventilation). Activities were repeated while wearing facemasks. When compared with quiet breathing, exertional respiratory activities increased particle counts 34.6‐fold during talking and 370.8‐fold during coughing (p < 0.001). High‐flow nasal oxygen 60 at l.min‐1 increased particle counts 2.3‐fold (p = 0.031) during quiet breathing. Single and dual circuit non‐invasive respiratory therapy at 25/10 cm.H2O with quiet breathing increased counts by 2.6‐fold and 7.8‐fold, respectively (both p < 0.001). During exertional activities, respiratory therapies and facemasks reduced emissions compared with activities alone. Respiratory activities (including exertional breathing and coughing) which mimic respiratory patterns during illness generate substantially more aerosols than non‐invasive respiratory therapies, which conversely can reduce total emissions. We argue the risk of aerosol exposure is underappreciated and warrants widespread, targeted interventions.
Here, absolute cross sections for the addition of s- and d-wave neutrons to 14C and 14N have been determined simultaneously via the (d,p) reaction at 10 MeV/u. The difference between the neutron and ...proton separation energies, ΔS, is around -20 MeV for the 14C+n system and +8 MeV for 14N+n. The population of the 1s1/2 and 0d5/2 orbitals for both systems is reduced by a factor of approximately 0.5 compared with the independent single-particle model, or about 0.6 when compared with the shell model. This finding strongly contrasts with results deduced from intermediate-energy knockout reactions between similar nuclei on targets of 9Be and 12C. The simultaneous technique used removes many systematic uncertainties.
We search for single-photon events in 53 fb^{-1} of e^{+}e^{-} collision data collected with the BABAR detector at the PEP-II B-Factory. We look for events with a single high-energy photon and a ...large missing momentum and energy, consistent with production of a spin-1 particle A^{'} through the process e^{+}e^{-}→γA^{'}; A^{'}→invisible. Such particles, referred to as "dark photons," are motivated by theories applying a U(1) gauge symmetry to dark matter. We find no evidence for such processes and set 90% confidence level upper limits on the coupling strength of A^{'} to e^{+}e^{-} in the mass range m_{A^{'}}≤8 GeV. In particular, our limits exclude the values of the A^{'} coupling suggested by the dark-photon interpretation of the muon (g-2)_{μ} anomaly, as well as a broad range of parameters for the dark-sector models.
Tropical cyclones (TCs) pose a significant threat to human health, and research is needed to identify high-risk subpopulations. We investigated whether hospitalization risks from TCs in Florida (FL), ...United States, varied across individuals and communities. We modeled the associations between all storms in FL from 1999 to 2016 and over 3.5 million Medicare hospitalizations for respiratory (RD) and cardiovascular disease (CVD). We estimated the relative risk (RR), comparing hospitalizations during TC-periods (2 days before to 7 days after) to matched non-TC-periods. We then separately modeled the associations in relation to individual and community characteristics. TCs were associated with elevated risk of RD hospitalizations (RR: 4.37, 95% CI: 3.08, 6.19), but not CVD (RR: 1.04, 95% CI: 0.87, 1.24). There was limited evidence of modification by individual characteristics (age, sex, or Medicaid eligibility); however, risks were elevated in communities with higher poverty or lower homeownership (for CVD hospitalizations) and in denser or more urban communities (for RD hospitalizations). More research is needed to understand the potential mechanisms and causal pathways that might account for the observed differences in the association between tropical cyclones and hospitalizations across communities.
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