Effects of anthropogenic emissions on aerosol formation from isoprene and monoterpenes in the southeastern United States

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

The lifetime of nitrogen oxides in an isoprene-dominated forest

The lifetime of nitrogen oxides (NO_x) affects the concentration and distribution of NO_x and the spatial patterns of nitrogen deposition. Despite its importance, the lifetime of NO_x is poorly constrained in rural and remote continental regions. We use measurements from a site in central Alabama during the Southern Oxidant and Aerosol Study (SOAS) in summer 2013 to provide new insights into the chemistry of NO_x and NO_x reservoirs. We find that the lifetime of NO_x during the daytime is controlled primarily by the production and loss of alkyl and multifunctional nitrates (ΣANs). During SOAS, ΣAN production was rapid, averaging 90 ppt h^(−1) during the day, and occurred predominantly during isoprene oxidation. Analysis of the ΣAN and HNO_3 budgets indicate that ΣANs have an average lifetime of under 2 h, and that approximately 45 % of the ΣANs produced at this site are rapidly hydrolyzed to produce nitric acid. We find that ΣAN hydrolysis is the largest source of HNO_3 and the primary pathway to permanent removal of NO_x from the boundary layer in this location. Using these new constraints on the fate of ΣANs, we find that the NO_x lifetime is 11 ± 5 h under typical midday conditions. The lifetime is extended by storage of NO_x in temporary reservoirs, including acyl peroxy nitrates and ΣANs

The U.S. Inland Creel and Angler Survey Catalog (CreelCat): Development, Applications, and Opportunities

Inland recreational fishing, defined as primarily leisure-driven fishing in freshwaters, is a popular pastime in the USA. State natural resource agencies endeavor to provide high-quality and sustainable fishing opportunities for anglers. Managers often use creel and other angler survey data to inform state- and waterbody-level management efforts. Despite the broad implementation of angler surveys and their importance to fisheries management at state scales, regional and national coordination among these activities is minimal, limiting data applicability for larger-scale management practices and research. Here, we introduce the U.S. Inland Creel and Angler Survey Catalog (CreelCat), a first-of-its-kind, publicly available national database of angler survey data that establishes a baseline of national inland recreational fishing metrics. We highlight research and management applications to help support sustainable inland recreational fishing practices, consider cautions, and make recommendations for implementation

Spongivory in the Wakatobi Marine National Park, Southeast Sulawesi, Indonesia

Sponges are functionally important coral reef fauna and there is strong evidence from the Caribbean that predation has important impacts on sponge-Assemblage dynamics; whether the same is true for Indo-Pacific sponges remains unknown. As a first step toward understanding the potential effects of spongivores on sponge diversity and abundance, we identified sponge predators at nine sites in Wakatobi Marine National Park, Indonesia, and conducted a short-Term caging experiment to examine the effects of excluding predators on noncryptic reef sponges at this location. Nudibranchs were the most abundant invertebrate spongivores, although their low densities are likely to limit their influence on sponges. Fish were the most abundant vertebrate spongivores with 16 species from six families observed feeding on sponges. Based on their abundance and our feeding observations, the fish with the greatest potential to influence sponge assemblages in Wakatobi Marine National Park were Zanclus cornutus, Chaetodon kleinii, Pygoplites diacanthus, and Pomacanthus sexstriatus. We did not detect an effect of excluding spongivores on noncryptic reef sponge abundance in our caging experiment, which may be due to these species having evolved chemical defenses against predators. Important areas for further research include the chemical ecology of Indo-Pacific sponges and whether spongivory currently restricts some species to cryptic or nonreef habitats

Atmospheric fates of Criegee intermediates in the ozonolysis of isoprene

We use a large laboratory, modeling, and field dataset to investigate the isoprene + O_3 reaction, with the goal of better understanding the fates of the C_1 and C_4 Criegee intermediates in the atmosphere. Although ozonolysis can produce several distinct Criegee intermediates, the C_1 stabilized Criegee (CH_2OO, 61 ± 9%) is the only one observed to react bimolecularly. We suggest that the C_4 Criegees have a low stabilization fraction and propose pathways for their decomposition. Both prompt and non-prompt reactions are important in the production of OH (28% ± 5%) and formaldehyde (81% ± 16%). The yields of unimolecular products (OH, formaldehyde, methacrolein (42 ± 6%) and methyl vinyl ketone (18 ± 6%)) are fairly insensitive to water, i.e., changes in yields in response to water vapor (≤4% absolute) are within the error of the analysis. We propose a comprehensive reaction mechanism that can be incorporated into atmospheric models, which reproduces laboratory data over a wide range of relative humidities. The mechanism proposes that CH_2OO + H_2O (k_((H_2O)) ∼ 1 × 10^(−15) cm^3 molec^(−1) s^(−1)) yields 73% hydroxymethyl hydroperoxide (HMHP), 6% formaldehyde + H_2O_2, and 21% formic acid + H_2O; and CH_2OO + (H_2O)_2 (k_((H_2O)_2) ∼ 1 × 10^(−12) cm^3 molec^(−1) s^(−1)) yields 40% HMHP, 6% formaldehyde + H_2O_2, and 54% formic acid + H_2O. Competitive rate determinations (k_(SO_2/k(H_2O)n=1,2) ∼ 2.2 (±0.3) × 10^4) and field observations suggest that water vapor is a sink for greater than 98% of CH2OO in a Southeastern US forest, even during pollution episodes ([SO_2] ∼ 10 ppb). The importance of the CH_2OO + (H_2O)n reaction is demonstrated by high HMHP mixing ratios observed over the forest canopy. We find that CH_2OO does not substantially affect the lifetime of SO_2 or HCOOH in the Southeast US, e.g., CH_2OO + SO_2 reaction is a minor contribution (<6%) to sulfate formation. Extrapolating, these results imply that sulfate production by stabilized Criegees is likely unimportant in regions dominated by the reactivity of ozone with isoprene. In contrast, hydroperoxide, organic acid, and formaldehyde formation from isoprene ozonolysis in those areas may be significant

Towards an Intelligent Tutor for Mathematical Proofs

Computer-supported learning is an increasingly important form of study since it allows for independent learning and individualized instruction. In this paper, we discuss a novel approach to developing an intelligent tutoring system for teaching textbook-style mathematical proofs. We characterize the particularities of the domain and discuss common ITS design models. Our approach is motivated by phenomena found in a corpus of tutorial dialogs that were collected in a Wizard-of-Oz experiment. We show how an intelligent tutor for textbook-style mathematical proofs can be built on top of an adapted assertion-level proof assistant by reusing representations and proof search strategies originally developed for automated and interactive theorem proving. The resulting prototype was successfully evaluated on a corpus of tutorial dialogs and yields good results.Comment: In Proceedings THedu'11, arXiv:1202.453

Effect of Convalescent Plasma on Organ Support-Free Days in Critically Ill Patients With COVID-19: A Randomized Clinical Trial

Importance: The evidence for benefit of convalescent plasma for critically ill patients with COVID-19 is inconclusive. Objective: To determine whether convalescent plasma would improve outcomes for critically ill adults with COVID-19. Design, Setting, and Participants: The ongoing Randomized, Embedded, Multifactorial, Adaptive Platform Trial for Community-Acquired Pneumonia (REMAP-CAP) enrolled and randomized 4763 adults with suspected or confirmed COVID-19 between March 9, 2020, and January 18, 2021, within at least 1 domain; 2011 critically ill adults were randomized to open-label interventions in the immunoglobulin domain at 129 sites in 4 countries. Follow-up ended on April 19, 2021. Interventions: The immunoglobulin domain randomized participants to receive 2 units of high-titer, ABO-compatible convalescent plasma (total volume of 550 mL ± 150 mL) within 48 hours of randomization (n = 1084) or no convalescent plasma (n = 916). Main Outcomes and Measures: The primary ordinal end point was organ support-free days (days alive and free of intensive care unit-based organ support) up to day 21 (range, -1 to 21 days; patients who died were assigned -1 day). The primary analysis was an adjusted bayesian cumulative logistic model. Superiority was defined as the posterior probability of an odds ratio (OR) greater than 1 (threshold for trial conclusion of superiority &gt;99%). Futility was defined as the posterior probability of an OR less than 1.2 (threshold for trial conclusion of futility &gt;95%). An OR greater than 1 represented improved survival, more organ support-free days, or both. The prespecified secondary outcomes included in-hospital survival; 28-day survival; 90-day survival; respiratory support-free days; cardiovascular support-free days; progression to invasive mechanical ventilation, extracorporeal mechanical oxygenation, or death; intensive care unit length of stay; hospital length of stay; World Health Organization ordinal scale score at day 14; venous thromboembolic events at 90 days; and serious adverse events. Results: Among the 2011 participants who were randomized (median age, 61 [IQR, 52 to 70] years and 645/1998 [32.3%] women), 1990 (99%) completed the trial. The convalescent plasma intervention was stopped after the prespecified criterion for futility was met. The median number of organ support-free days was 0 (IQR, -1 to 16) in the convalescent plasma group and 3 (IQR, -1 to 16) in the no convalescent plasma group. The in-hospital mortality rate was 37.3% (401/1075) for the convalescent plasma group and 38.4% (347/904) for the no convalescent plasma group and the median number of days alive and free of organ support was 14 (IQR, 3 to 18) and 14 (IQR, 7 to 18), respectively. The median-adjusted OR was 0.97 (95% credible interval, 0.83 to 1.15) and the posterior probability of futility (O