Significance Atmospheric secondary organic aerosol has substantial impacts on climate, air quality, and human health. However, the formation mechanisms of secondary organic aerosol remain uncertain, ...especially on how anthropogenic pollutants (from human activities) control aerosol formation from biogenic volatile organic compounds (emitted by vegetation) and the magnitude of anthropogenic influences. Although possible mechanisms have been proposed based on laboratories studies, a coherent understanding of anthropogenic−biogenic interactions in ambient environments has not emerged. Here, we provide direct observational evidence that secondary organic aerosol formed from biogenic isoprene and monoterpenes is greatly mediated by anthropogenic SO ₂ and NO ₓ emissions based on integrated ambient measurements and laboratory studies.
Secondary organic aerosol (SOA) constitutes a substantial fraction of fine particulate matter and has important impacts on climate and human health. The extent to which human activities alter SOA formation from biogenic emissions in the atmosphere is largely undetermined. Here, we present direct observational evidence on the magnitude of anthropogenic influence on biogenic SOA formation based on comprehensive ambient measurements in the southeastern United States (US). Multiple high-time-resolution mass spectrometry organic aerosol measurements were made during different seasons at various locations, including urban and rural sites in the greater Atlanta area and Centreville in rural Alabama. Our results provide a quantitative understanding of the roles of anthropogenic SO ₂ and NO ₓ in ambient SOA formation. We show that isoprene-derived SOA is directly mediated by the abundance of sulfate, instead of the particle water content and/or particle acidity as suggested by prior laboratory studies. Anthropogenic NO ₓ is shown to enhance nighttime SOA formation via nitrate radical oxidation of monoterpenes, resulting in the formation of condensable organic nitrates. Together, anthropogenic sulfate and NO ₓ can mediate 43–70% of total measured organic aerosol (29–49% of submicron particulate matter, PM ₁) in the southeastern US during summer. These measurements imply that future reduction in SO ₂ and NO ₓ emissions can considerably reduce the SOA burden in the southeastern US. Updating current modeling frameworks with these observational constraints will also lead to more accurate treatment of aerosol formation for regions with substantial anthropogenic−biogenic interactions and consequently improve air quality and climate simulations.
ABSTRACT
We use observations from the Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey to explore the relationship between stellar parameters and multiplicity. We combine ...high-resolution repeat spectroscopy for 41 363 dwarf and subgiant stars with abundance measurements from the APOGEE pipeline and distances and stellar parameters derived using Gaia DR2 parallaxes from Sanders & Das to identify and characterize stellar multiples with periods below 30 yr, corresponding to ΔRVmax ≳ 3 km s−1, where ΔRVmax is the maximum APOGEE-detected shift in the radial velocities. Chemical composition is responsible for most of the variation in the close binary fraction in our sample, with stellar parameters like mass and age playing a secondary role. In addition to the previously identified strong anticorrelation between the close binary fraction and Fe/H, we find that high abundances of α elements also suppress multiplicity at most values of Fe/H sampled by APOGEE. The anticorrelation between α abundances and multiplicity is substantially steeper than that observed for Fe, suggesting C, O, and Si in the form of dust and ices dominate the opacity of primordial protostellar discs and their propensity for fragmentation via gravitational stability. Near Fe/H = 0 dex, the bias-corrected close binary fraction (a < 10 au) decreases from ≈100 per cent at α/H = −0.2 dex to ≈15 per cent near α/H = 0.08 dex, with a suggestive turn-up to ≈20 per cent near α/H = 0.2. We conclude that the relationship between stellar multiplicity and chemical composition for sun-like dwarf stars in the field of the Milky Way is complex, and that this complexity should be accounted for in future studies of interacting binaries.
The chemical complexity of atmospheric organic aerosol (OA) has caused substantial uncertainties in understanding its origins and environmental impacts. Here, we provide constraints on OA origins ...through compositional characterization with molecular-level details. Our results suggest that secondary OA (SOA) from monoterpene oxidation accounts for approximately half of summertime fine OA in Centreville, AL, a forested area in the southeastern United States influenced by anthropogenic pollution. We find that different chemical processes involving nitrogen oxides, during days and nights, play a central role in determining the mass of monoterpene SOA produced. These findings elucidate the strong anthropogenic–biogenic interaction affecting ambient aerosol in the southeastern United States and point out the importance of reducing anthropogenic emissions, especially under a changing climate, where biogenic emissions will likely keep increasing.
Remarkable productivity has been achieved in crop species through artificial selection and adaptation to modern agronomic practices. Whether intensive selection has changed the ability of improved ...cultivars to maintain high productivity across variable environments is unknown. Understanding the genetic control of phenotypic plasticity and genotype by environment (G × E) interaction will enhance crop performance predictions across diverse environments. Here we use data generated from the Genomes to Fields (G2F) Maize G × E project to assess the effect of selection on G × E variation and characterize polymorphisms associated with plasticity. Genomic regions putatively selected during modern temperate maize breeding explain less variability for yield G × E than unselected regions, indicating that improvement by breeding may have reduced G × E of modern temperate cultivars. Trends in genomic position of variants associated with stability reveal fewer genic associations and enrichment of variants 0-5000 base pairs upstream of genes, hypothetically due to control of plasticity by short-range regulatory elements.
Filtergraph is a web application being developed and maintained by the Vanderbilt Initiative in Data-intensive Astrophysics (VIDA) to flexibly and rapidly visualize a large variety of astronomy ...datasets of various formats and sizes. The user loads a flat-file dataset into Filtergraph which automatically generates an interactive data portal that can be easily shared with others. From this portal, the user can immediately generate scatter plots of up to five dimensions as well as histograms and tables based on the dataset. Key features of the portal include intuitive controls with auto-completed variable names, the ability to filter the data in real time through user-specified criteria, the ability to select data by dragging on the screen, and the ability to perform arithmetic operations on the data in real time. To enable seamless data visualization and exploration, changes are quickly rendered on screen and visualizations can be exported as high quality graphics files. The application is optimized for speed in the context of large datasets: for instance, a plot generated from a stellar database of 3.1 million entries renders in less than 2 s on a standard web server platform. This web application has been created using the Web2py web framework based on the Python programming language. Filtergraph is free to use at http://filtergraph.vanderbilt.edu/.
•We developed a web-based application for visualization of astronomy data.•The user can generate publication quality multi-dimensional plots and tables.•Designed for speed, the user can instantly interact with and visualize the data.•To enhance collaboration, data and visualizations can be shared via simple URL.•This web application can accept data in a wide variety of file formats.
Background: Pediatric community-acquired pneumonia (CAP) can lead to long-term respiratory sequelae, including bronchiectasis. We determined if an extended (13–14 days) versus standard (5–6 days) ...antibiotic course improves long-term outcomes in children hospitalized with CAP from populations at high risk of chronic respiratory disease. Methods: We undertook a multicenter, double-blind, superiority, randomized controlled trial involving 7 Australian, New Zealand, and Malaysian hospitals. Children aged 3 months to ≤5 years hospitalized with radiographic-confirmed CAP who received 1–3 days of intravenous antibiotics, then 3 days of oral amoxicillin-clavulanate, were randomized to either extended-course (8-day oral amoxicillin-clavulanate) or standard-course (8-day oral placebo) arms. Children were reviewed at 12 and 24 months. The primary outcome was children with the composite endpoint of chronic respiratory symptoms/signs (chronic cough at 12 and 24 months; ≥1 subsequent hospitalized acute lower respiratory infection by 24 months; or persistent and/or new chest radiographic signs at 12-months) at 24-months postdischarge, analyzed by intention-to-treat, where children with incomplete follow-up were assumed to have chronic respiratory symptoms/signs (“worst-case” scenario). Results: A total of 324 children were randomized extended-course (n = 163), standard-course (n = 161). For our primary outcome, chronic respiratory symptoms/signs occurred in 97/163 (60%) and 94/161 (58%) children in the extended-courses and standard-courses, respectively relative risk (RR) = 1.02, 95% confidence interval (CI): 0.85–1.22. Among children where all sub-composite outcomes were known, chronic respiratory symptoms/signs between groups, RR = 1.10, 95% CI: 0.69–1.76 extended-course = 27/93 (29%) and standard-course = 24/91 (26%). Additional sensitivity analyses also revealed no between-group differences. Conclusion: Among children from high-risk populations hospitalized with CAP, 13–14 days of antibiotics (versus 5–6 days), did not improve long-term respiratory outcomes.
High-level evidence is limited for antibiotic duration in children hospitalized with community-acquired pneumonia (CAP) from First Nations and other at-risk populations of chronic respiratory ...disorders. As part of a larger study, we determined whether an extended antibiotic course is superior to a standard course for achieving clinical cure at 4 weeks in children 3 months to ≤5 years old hospitalized with CAP.
In our multinational (Australia, New Zealand, Malaysia), double-blind, superiority randomized controlled trial, children hospitalized with uncomplicated, radiographic-confirmed, CAP received 1-3 days of intravenous antibiotics followed by 3 days of oral amoxicillin-clavulanate (80 mg/kg, amoxicillin component, divided twice daily) and then randomized to extended (13-14 days duration) or standard (5-6 days) antibiotics. The primary outcome was clinical cure (complete resolution of respiratory symptoms/signs) 4 weeks postenrollment. Secondary outcomes included adverse events, nasopharyngeal bacterial pathogens and antimicrobial resistance at 4 weeks.
Of 372 children enrolled, 324 fulfilled the inclusion criteria and were randomized. Using intention-to-treat analysis, between-group clinical cure rates were similar (extended course: n = 127/163, 77.9%; standard course: n = 131/161, 81.3%; relative risk = 0.96, 95% confidence interval = 0.86-1.07). There were no significant between-group differences for adverse events (extended course: n = 43/163, 26.4%; standard course, n = 32/161, 19.9%) or nasopharyngeal carriage of Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis and Staphylococcus aureus or antimicrobial resistance.
Among children hospitalized with pneumonia and at-risk of chronic respiratory illnesses, an extended antibiotic course was not superior to a standard course at achieving clinical cure at 4 weeks. Additional research will identify if an extended course provides longer-term benefits.
We report the discovery of a low-mass companion orbiting the metal-rich, main sequence F star TYC 2949-00557-1 during the Multi-object APO Radial Velocity Exoplanet Large-area Survey (MARVELS) pilot ...project. The host star has an effective temperature T{sub eff} = 6135 {+-} 40 K, logg = 4.4 {+-} 0.1, and Fe/H = 0.32 {+-} 0.01, indicating a mass of M = 1.25 {+-} 0.09 M{sub sun} and R = 1.15 {+-} 0.15 R{sub sun}. The companion has an orbital period of 5.69449 {+-} 0.00023 days and straddles the hydrogen burning limit with a minimum mass of 64 M{sub J} , and thus may be an example of the rare class of brown dwarfs orbiting at distances comparable to those of 'Hot Jupiters'. We present relative photometry that demonstrates that the host star is photometrically stable at the few millimagnitude level on time scales of hours to years, and rules out transits for a companion of radius {approx}>0.8 R{sub J} at the 95% confidence level. Tidal analysis of the system suggests that the star and companion are likely in a double synchronous state where both rotational and orbital synchronization have been achieved. This is the first low-mass companion detected with a multi-object, dispersed, fixed-delay interferometer.
IntroductionEarly childhood pneumonia is a common problem globally with long-term complications that include bronchiectasis and chronic obstructive pulmonary disease. It is biologically plausible ...that these long-term effects may be minimised in young children at increased risk of such sequelae if any residual lower airway infection and inflammation in their developing lungs can be treated successfully by longer antibiotic courses. In contrast, shortened antibiotic treatments are being promoted because of concerns over inducing antimicrobial resistance. Nevertheless, the optimal treatment duration remains unknown. Outcomes from randomised controlled trials (RCTs) on paediatric pneumonia have focused on short-term (usually <2 weeks) results. Indeed, no long-term RCT-generated outcome data are available currently. We hypothesise that a longer antibiotic course, compared with the standard treatment course, reduces the risk of chronic respiratory symptoms/signs or bronchiectasis 24 months after the original pneumonia episode.Methods and analysisThis multicentre, parallel, double-blind, placebo-controlled randomised trial involving seven hospitals in six cities from three different countries commenced in May 2016. Three-hundred-and-fourteen eligible Australian Indigenous, New Zealand Māori/Pacific and Malaysian children (aged 0.25 to 5 years) hospitalised for community-acquired, chest X-ray (CXR)-proven pneumonia are being recruited. Following intravenous antibiotics and 3 days of amoxicillin-clavulanate, they are randomised (stratified by site and age group, allocation-concealed) to receive either: (i) amoxicillin-clavulanate (80 mg/kg/day (maximum 980 mg of amoxicillin) in two-divided doses or (ii) placebo (equal volume and dosing frequency) for 8 days. Clinical data, nasopharyngeal swab, bloods and CXR are collected. The primary outcome is the proportion of children without chronic respiratory symptom/signs of bronchiectasis at 24 months. The main secondary outcomes are ‘clinical cure’ at 4 weeks, time-to-next respiratory-related hospitalisation and antibiotic resistance of nasopharyngeal respiratory bacteria.Ethics and disseminationThe Human Research Ethics Committees of all the recruiting institutions (Darwin: Northern Territory Department of Health and Menzies School of Health Research; Auckland: Starship Children’s and KidsFirst Hospitals; East Malaysia: Likas Hospital and Sarawak General Hospital; Kuala Lumpur: University of Malaya Research Ethics Committee; and Klang: Malaysian Department of Health) have approved the research protocol version 7 (13 August 2018). The RCT and other results will be submitted for publication.Trial registrationACTRN12616000046404.
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