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The technical viability of future fusion power plants is influenced by several factors, including whether they can be maintained through remote means. The plant design needs to be aligned with the capability of remote maintenance equipment, but determining this parameter requires labor-intensive analysis that draws from a wide variety of sources. Automating the analysis is vital for remote maintenance to evaluate more DEMO plant variants, consistently and in more detail, and to enable the work of other system designers. We build on work by previous groups to automate the process of determining maintainability. Our aim is to incorporate an assessment of feasibility. Typical examples of feasibility assessment include clash analysis of dexterous actions and collision detection for movements of large transport modules around the plant. Feasibility can also be affected indirectly. We explore how radiation models can be used to assess the impact of dose accumulation on downtime, i.e., the time needed to restore irradiated equipment using fresh spares. This work presents efforts to automate fast and consistent maintenance duration calculations through integration of space, radiation assessment, and systems engineering approaches. Ultimately, the work is intended to be part of a design verification and optimization toolkit to substantiate DEMO plant availability.

X-ray photoemission and X-ray absorption spectroscopy are important techniques to characterize chemical bonding at surfaces and are often used to identify the strength and nature of adsorbate–substrate interactions. In this study, we judge the ability of X-ray spectroscopic techniques to identify different regimes of chemical bonding at metal–organic interfaces. To achieve this, we sample different interaction strength regimes in a comprehensive and systematic way by comparing two topological isomers, azulene and naphthalene, adsorbed on three metal substrates with varying reactivity, namely the (111) facets of Ag, Cu, and Pt. Using density functional theory, we simulate core-level binding energies and X-ray absorption spectra of the molecular carbon species. The simulated spectra reveal three distinct characteristics based on the molecule-specific spectral features which we attribute to types of surface chemical bonding with varying strength. We find that weak physisorption only leads to minor changes compared to the gas-phase spectra, weak chemisorption leads to charge transfer and significant spectral changes, and strong chemisorption leads to a loss of the molecule-specific features in the spectra. The classification we provide is aimed at assisting interpretation of experimental X-ray spectra for complex metal–organic interfaces.

Defects play a critical role for the functionality and performance of materials, but the understanding of the related effects is often lacking, because the typically low concentrations of defects make them difficult to study. A prominent case is the topological defects in two-dimensional materials such as graphene. The performance of graphene-based (opto-)electronic devices depends critically on the properties of the graphene/metal interfaces at the contacting electrodes. The question of how these interface properties depend on the ubiquitous topological defects in graphene is of high practical relevance, but could not be answered so far. Here, we focus on the prototypical Stone–Wales (S–W) topological defect and combine theoretical analysis with experimental investigations of molecular model systems. We show that the embedded defects undergo enhanced bonding and electron transfer with a copper surface, compared to regular graphene. These findings are experimentally corroborated using molecular models, where azupyrene mimics the S–W defect, while its isomer pyrene represents the ideal graphene structure. Experimental interaction energies, electronic-structure analysis, and adsorption distance differences confirm the defect-controlled bonding quantitatively. Our study reveals the important role of defects for the electronic coupling at graphene/metal interfaces and suggests that topological defect engineering can be used for performance control.

Generally speaking, that period before or during your junior year can be pivotal to a successful senior year. Building a comprehensive network of friends, family members, professors and corporate connections […]

Background and aimsSustained virological suppression and hepatitis B surface antigen (HBsAg) loss have been described after nucleot(s)ide analogue (NA) discontinuation for patients with hepatitis B e antigen (HBeAg)-negative chronic hepatitis B (CHB). We performed a meta-analysis of the clinical outcomes after NA discontinuation for HBeAg-negative CHB.MethodsStudies involving NA cessation in HBeAg-negative CHB individuals with a median follow-up of ≥12 months were included. Participants were HBeAg-negative at the time of NA initiation. Random effects meta-analyses were performed for the following clinical outcomes: (1) virological relapse (VR) at 6 and 12 months; (2) clinical relapse (CR) at 6 and 12 months and (3) HBsAg loss. Effect of other variables was estimated using subgroup analysis and meta-regression. Studies including patients stopping entecavir (ETV) and/or tenofovir disoproxil fumarate (TDF) were considered separately to studies including patients stopping older generation NA.ResultsN=37 studies met inclusion criteria. Cumulative incidence of VR and CR after stopping ETV/TDF was 44% and 17% at 6 months and 63% and 35% at 12 months. Similar relapse rates were observed after stopping older NAs. Among patients stopping ETV/TDF, TDF cessation was associated with increased CR rates at 6 months versus ETV. There was an association between follow-up ≥4 years and HBsAg loss rates when stopping older NAs. Hepatic decompensation and hepatocellular carcinoma were rare but occurred more frequently in studies including cirrhotic individuals.ConclusionVR is common after NA discontinuation, however, CR was only seen in one-third of patients at 12 months. Stopping NA therapy can be followed by HBsAg clearance, and rates are higher with longer follow-up.

Introduction: Spinal cord stimulation (SCS) is a recommended treatment for chronic refractory neuropathic pain. During the COVID-19 pandemic, elective procedures have been postponed indefinitely both to provide capacity to deal with the emergency caseload and to avoid exposure of elective patients to COVID-19. This survey aimed to explore the effect of the pandemic on chronic pain in this group and the views of patients towards undergoing SCS treatment when routine services should resume.Methods: This was a prospective, multi-centre telephone patient survey that analysed data from 330 patients with chronic pain who were on an SCS waiting list. Questions focussed on severity of pain, effect on mental health, medication consumption and reliance on support networks during the COVID-19 pandemic. Views towards undergoing SCS therapy were also ascertained. Counts and percentages were generated, and chi-square tests of independence explored the impact of COVID-19 risk (very high, high, low) on survey responses.Results: Pain, mental health and patient’s ability to self-manage pain deteriorated in around 47%, 50% and 38% of patients, respectively. Some patients reported increases in pain medication consumption (37%) and reliance on support network (41%). Patients showed a willingness to attend for COVID-19 testing (92%), self-isolate prior to SCS (94%) and undergo the procedure as soon as possible (76%).Conclusion: Our findings suggest that even during the COVID-19 pandemic, there remains a strong clinical need for patients with chronic pain identified as likely SCS responders to be treated quickly. The current prioritisation of new SCS at category 4 (delayed more than 3 months) is challenged judging by this national survey. These patients are awaiting SCS surgery to relieve severe intractable neuropathic pain. A priority at category 3 (delayed up to 3 months) or in some selected cases, at category 2 are the appropriate priority categories.

Wildfires are an important source of nitrous acid (HONO), a photolabile radical precursor, yet in situ measurements and quantification of primary HONO emissions from open wildfires have been scarce. We present airborne observations of HONO within wildfire plumes sampled during the Western Wildfire Experiment for Cloud chemistry, Aerosol absorption and Nitrogen (WE-CAN) campaign. ΔHONO/ΔCO close to the fire locations ranged from 0.7 to 17 pptv ppbv–1using a maximum enhancement method, with the median similar to previous observations of temperate forest fire plumes. Measured HONO to NOxenhancement ratios were generally factors of 2, or higher, at early plume ages than previous studies. Enhancement ratios scale with modified combustion efficiency and certain nitrogenous trace gases, which may be useful to estimate HONO release when HONO observations are lacking or plumes have photochemical exposures exceeding an hour as emitted HONO is rapidly photolyzed. We find that HONO photolysis is the dominant contributor to hydrogen oxide radicals (HOx= OH + HO2) in early stage (<3 h) wildfire plume evolution. These results highlight the role of HONO as a major component of reactive nitrogen emissions from wildfires and the main driver of initial photochemical oxidation.

The performance of graphene-based (opto)electronic devices depends critically on the graphene/metal interface formed at the metal contacts. We show here that the interface properties may be controlled by topological defects, such as the pentagon–heptagon (5–7) pairs, because of their strongly enhanced bonding to the metal. To measure the bond energy and other key properties not accessible for the embedded defects, we use azulene as a molecular model for the 5–7 defect. Comparison to its isomer naphthalene, which represents the regular graphene structure, reveals that azulene interacts more strongly with a Pt(111) surface. Its adsorption energy, as measured by single-crystal adsorption calorimetry (SCAC), exceeds that of naphthalene by up to 116 kJ/mol (or up to 50%). Both isomers undergo hybridization of their frontier orbitals with metal states, as indicated by X-ray and ultraviolet photoelectron spectroscopy (XPS/UPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy combined with molecular orbital (MO) projection analysis through dispersion-corrected, periodic density functional theory (DFT) calculations. Based on the NEXAFS/DFT analysis, the stronger bond of the 5–7 system is attributed to the different energetic response of its unoccupied frontier orbitals to adsorption. Adsorption-induced bond-length changes show substantial topology-related differences between the isomers. Electron transfer occurs in both directions through donation/back-donation, resulting in the partial occupation (deoccupation) of formerly unoccupied (occupied) orbitals, as revealed by periodic energy decomposition analysis (pEDA) for extended systems. Our model study shows that the topology of the π-electron system strongly affects its bonding to a transition metal and thus can be utilized to tailor interface properties.

Interfaces between polycyclic π-electron systems and metals play prominent roles in organic or graphene-based (opto)electronic devices, in which performance-related parameters depend critically on the properties of metal/semiconductor contacts. Here, we explore how the topology of the π-electron system influences the bonding and the electronic properties of the interface. We use azulene as a model for nonalternant pentagon–heptagon (5–7) ring pairs and compare it to its isomer naphthalene, which represents the alternant 6–6 ring pair. Their coverage-dependent interaction with Ag(111) and Cu(111) surfaces was studied with the normal-incidence X-ray standing wave (NIXSW) technique, near-edge X-ray absorption fine structure (NEXAFS) spectroscopy, UV and X-ray photoelectron spectroscopies (UPS and XPS), and density functional theory (DFT). Coverage-dependent adsorption heights and spectroscopic data reveal that azulene forms shorter interfacial bonds than naphthalene and engages in stronger electronic interactions with both surfaces. These differences are more pronounced on Cu. Increasing coverages lead to larger adsorption heights, indicating bond weakening by intermolecular repulsion. The extensive DFT calculations include dispersive interactions using (1) the DFT-D3 scheme, (2) the vdWsurfcorrection based on DFT-TS, (3) a many-body dispersion (MBD) correction scheme, and (4) the D3surfscheme. All methods predict the adsorption heights reasonably well with an average error below 0.1 Å. The stronger bond of azulene is attributed to its nonalternant topology, which results in a reduced highest occupied molecular orbital (HOMO)–lowest occupied molecular orbital (LUMO) gap and brings the LUMO energetically close to the Fermi energy of the metal, causing stronger hybridization with electronic states of the metal surfaces.

Sulfur dioxide (SO2) is emitted in large quantities from coal‐burning power plants and leads to various harmful health and environmental effects. In this study, we use plume intercepts from the Wintertime INvestigation of Transport, Emission and Reactivity (WINTER) campaign to estimate the oxidation rates of SO2under wintertime conditions and the factors that determine SO2removal. Observations suggest that OH governs the rate SO2oxidation in the eastern United States during winter. The range of mean oxidation rates during the day from power plants were 0.22–0.71%/hr, producing SO2lifetimes of 13–43 days, if SO2consumption is assumed to occur during 10.5 hr of daylight in cloudless conditions. Though most nighttime rate measurements were zero within uncertainty, there is some evidence of nighttime removal, which suggests alternate oxidation mechanisms. The fastest nighttime observed SO2oxidation rate was 0.25±0.07%/hr, producing a combined day/night SO2lifetime of 8.5–21 days. The upper limit of the oxidation rate (the mean+1σof the fastest day and night observations) is 16.5%/day, corresponding to a lifetime of 6.1 days. The analysis also quantifies the primary emission of sulfate from power plants. The median mole percentage of SO4‐2from observed plumes was 1.7% and the mean percentage sulfate was 2.8% for intercepts within 1 hr of transit to power plants. The largest value observed from close intercepts was over 7% sulfate, and the largest extrapolated value was 18%, based on intercepts further from their source and fastest observed oxidation rate. The daytime conversion rate of SO2to SO4‐2was 0.22‐0.71%/hr in winter under clear‐sky conditions, with lifetimes of 140‐450 hrFor 10.5 hr of daylight, the upper limit of the oxidation rate is 16.5%/day, corresponding to a lifetime of 6.1 daysDirect emissions of SO4‐2relative to total sulfur (SO2+ SO4‐2) had mean and median values of 1.7% and 2.8%, respectively

We report airborne measurements of acetaldehyde (CH3CHO) during the first and second deployments of the National Aeronautics and Space Administration Atmospheric Tomography Mission (ATom). The budget of CH3CHO is examined using the Community Atmospheric Model with chemistry (CAM‐chem), with a newly developed online air‐sea exchange module. The upper limit of the global ocean net emission of CH3CHO is estimated to be 34 Tg/a (42 Tg/a if considering bubble‐mediated transfer), and the ocean impacts on tropospheric CH3CHO are mostly confined to the marine boundary layer. Our analysis suggests that there is an unaccounted CH3CHO source in the remote troposphere and that organic aerosols can only provide a fraction of this missing source. We propose that peroxyacetic acid is an ideal indicator of the rapid CH3CHO production in the remote troposphere. The higher‐than‐expected CH3CHO measurements represent a missing sink of hydroxyl radicals (and halogen radical) in current chemistry‐climate models. The Earth's atmosphere and its ability to self‐regulate and cleanse itself is dependent on a complex interplay of trace chemical species, some of which are emitted from the biosphere, while others are from human activities or fires. One of these key species, acetaldehyde, was measured as part of the recent Atmospheric Tomography Mission, an aircraft (National Aeronautics and Space Administration DC‐8) experiment transecting the lengths of the Pacific and Atlantic Oceans during two seasons, measuring greenhouse gases and chemically reactive gases and particles. These measurements allow us to test our ability to model the chemical state of the atmosphere. The results indicate that the ocean is a large source of acetaldehyde and the analysis here suggests additional mechanisms that narrow the gap between observations and simulations but also reveal that an additional unexplained source or sources remain(s) in the remote free troposphere. It is critical to understand this missing carbon source because it has significant implications for understanding the cycle of oxidants which, in turn, provide for the means of removing (cleaning) trace gases including methane, an important greenhouse gas, from the atmosphere. Observed acetaldehyde (CH3CHO) in the remote troposphere is compatible with observed peroxyacetic acid (PAA) within uncertaintiesWe speculate that there is a missing CH3CHO source in the remote atmosphere and observed organic aerosols cannot explain the observed CH3CHOThe ocean is a net source of CH3CHO; the ocean biogeochemistry control on the atmospheric chemistry warrants further investigation

Heterogeneous chemical cycles of pyrogenic nitrogen and halides influence tropospheric ozone and affect the stratosphere during extreme Pyrocumulonimbus (PyroCB) events. We report field‐derived N2O5uptake coefficients, γ(N2O5), and ClNO2yields, φ(ClNO2), from two aircraft campaigns observing fresh smoke in the lower and mid troposphere and processed/aged smoke in the upper troposphere and lower stratosphere (UTLS). Derived φ(ClNO2) varied across the full 0–1 range but was typically <0.5 and smallest in a PyroCB (<0.05). Derived γ(N2O5) was low in agricultural smoke (0.2–3.6 × 10−3), extremely low in mid‐tropospheric wildfire smoke (0.1 × 10−3), but larger in PyroCB processed smoke (0.7–5.0 × 10−3). Aged biomass burning aerosol in the UTLS had a higher γ(N2O5) of 17 × 10−3that increased with sulfate and liquid water, but that was 1–2 orders of magnitude lower than values for aqueous sulfuric aerosol used in stratospheric models. The injection of reactive material into Earth's atmosphere from fires affects atmospheric composition at regional and hemispheric scales. Reported stratospheric ozone depletion during extreme events, such as the 2020 Australian wildfires, illustrates one example of fire impacts and the role of heterogeneous (gas‐particle) processes. We report field quantification of rates and product yields from airborne observations of smoke. Extremely slow heterogeneous reaction rates on young smoke increase with transport and aging, but upper atmospheric values are still a factor of 10 slower than parameterizations used in stratospheric models. Heterogeneous production of ClNO2, a major lower atmospheric chlorine activation pathway, may be active on biomass burning aerosol in the upper atmosphere. ClNO2formation is active on biomass burning (BB) particles but decreases with transport to the upper troposphere and lower stratosphere (UTLS)N2O5uptake coefficients are low on young BB smoke and increase with transport through a PyroCB and UTLS agingN2O5uptake coefficients on aged BB particles in the UTLS are significantly lower than those used in model parameterizations ClNO2formation is active on biomass burning (BB) particles but decreases with transport to the upper troposphere and lower stratosphere (UTLS) N2O5uptake coefficients are low on young BB smoke and increase with transport through a PyroCB and UTLS aging N2O5uptake coefficients on aged BB particles in the UTLS are significantly lower than those used in model parameterizations

August/September Arriving fresh from your summer work experience, you are ready to tackle your senior year. Unfortunately, it is too late now to do some of the things you should [...]

The concentration of nitrogen oxides (NOx) plays a central role in controlling air quality. On a global scale, the primary sink of NOxis oxidation to form HNO3. Gas-phase HNO3photolyses slowly with a lifetime in the troposphere of 10 days or more. However, several recent studies examining HONO chemistry have proposed that particle-phase HNO3undergoes photolysis 10–300 times more rapidly than gas-phase HNO3. We present here constraints on the rate of particle-phase HNO3photolysis based on observations of NOxand HNO3collected over the Yellow Sea during the KORUS-AQ study in summer 2016. The fastest proposed photolysis rates are inconsistent with the observed NOxto HNO3ratios. Negligible to moderate enhancements of the HNO3photolysis rate in particles, 1–30 times faster than in the gas phase, are most consistent with the observations. Small or moderate enhancement of particle-phase HNO3photolysis would not significantly affect the HNO3budget but could help explain observations of HONO and NOxin highly aged air.

We quantify the stratospheric injection of brominated very short‐lived substances (VSLS) based on aircraft observations acquired in winter 2014 above the Tropical Western Pacific during the CONvective TRansport of Active Species in the Tropics (CONTRAST) and the Airborne Tropical TRopopause EXperiment (ATTREX) campaigns. The overall contribution of VSLS to stratospheric bromine was determined to be 5.0 ± 2.1 ppt, in agreement with the 5 ± 3 ppt estimate provided in the 2014 World Meteorological Organization (WMO) Ozone Assessment report (WMO 2014), but with lower uncertainty. Measurements of organic bromine compounds, including VSLS, were analyzed using CFC‐11 as a reference stratospheric tracer. From this analysis, 2.9 ± 0.6 ppt of bromine enters the stratosphere via organic source gas injection of VSLS. This value is two times the mean bromine content of VSLS measured at the tropical tropopause, for regions outside of the Tropical Western Pacific, summarized in WMO 2014. A photochemical box model, constrained to CONTRAST observations, was used to estimate inorganic bromine from measurements of BrO collected by two instruments. The analysis indicates that 2.1 ± 2.1 ppt of bromine enters the stratosphere via inorganic product gas injection. We also examine the representation of brominated VSLS within 14 global models that participated in the Chemistry‐Climate Model Initiative. The representation of stratospheric bromine in these models generally lies within the range of our empirical estimate. Models that include explicit representations of VSLS compare better with bromine observations in the lower stratosphere than models that utilize longer‐lived chemicals as a surrogate for VSLS. Based on winter 2014 observations, very short‐lived bromocarbons produced by oceanic biology contribute 5 ± 2 ppt to stratospheric bromineOf the bromine from very short‐lived substances that reaches the stratosphere, 60% enters as organic species and 40% as inorganic speciesRepresentation of stratospheric bromine within global models is greatly improved upon consideration of very short‐lived bromocarbons

Nocturnal dinitrogen pentoxide (N2O5) heterogeneous chemistry impacts regional air quality and the distribution and lifetime of tropospheric oxidants. Formed from the oxidation of nitrogen oxides, N2O5is heterogeneously lost to aerosol with a highly variable reaction probability, γ(N2O5), dependent on aerosol composition and ambient conditions. Reaction products include soluble nitrate (HNO3or NO3−) and nitryl chloride (ClNO2). We report the first‐ever derivations of γ(N2O5) from ambient wintertime aircraft measurements in the critically important nocturnal residual boundary layer. Box modeling of the 2015 Wintertime INvestigation of Transport, Emissions, and Reactivity (WINTER) campaign over the eastern United States derived 2,876 individual γ(N2O5) values with a median value of 0.0143 and range of 2 × 10−5to 0.1751. WINTER γ(N2O5) values exhibited the strongest correlation with aerosol water content, but weak correlations with other variables, such as aerosol nitrate and organics, suggesting a complex, nonlinear dependence on multiple factors, or an additional dependence on a nonobserved factor. This factor may be related to aerosol phase, morphology (i.e., core shell), or mixing state, none of which are commonly measured during aircraft field studies. Despite general agreement with previous laboratory observations, comparison of WINTER data with 14 literature parameterizations (used to predict γ(N2O5) in chemical transport models) confirms that none of the current methods reproduce the full range of γ(N2O5) values. Nine reproduce the WINTER median within a factor of 2. Presented here is the first field‐based, empirical parameterization of γ(N2O5), fit to WINTER data, based on the functional form of previous parameterizations. Aircraft measurements over the eastern United States provide the largest number of N2O5uptake coefficient γ(N2O5) determinations during winterDespite a large range and variability, several γ(N2O5) dependencies are statistically significant, particularly with aerosol liquid waterStandard γ(N2O5) parameterizations do not capture the variability but several, including an empirical form derived here, capture the median

BackgroundMany adolescents are exposed to nicotine via smoking, e-cigarette use, or second-hand smoke. Nicotine-induced renal oxidative stress and its long-term consequences may be higher in adolescents than in adults because of intrinsic factors in the adolescent kidney.MethodsAdolescent and adult male C57Bl/6J mice were subjected to 2 or 200?µg/ml nicotine, which closely emulates passive or active smoking, respectively, for 4 weeks. Extent of nicotine exposure (cotinine content), oxidative stress (HNE), renal function (creatinine), tubular injury (KIM-1), and pretreatment renal levels of select pro-oxidant (p66shc) and antioxidant (Nrf2/MnSOD) genes were determined. Impact of p66shc overexpression or Nrf2/MnSOD knockdown on low-/high-dose nicotine-induced oxidative stress was determined in cultured renal proximal tubule cells.ResultsDespite similar plasma/renal cotinine levels, renal HNE and KIM-1 contents were higher in adolescents compared with those in adults, whereas renal function was unaltered after passive or active smoking-equivalent nicotine exposure. Pretreatment levels of p66shc were higher, whereas Nrf2/MnSOD levels were lower in the adolescent kidney. In agreement with this, overexpression of p66shc or knockdown of Nrf2/MnSOD augmented nicotine-induced ROS production in renal proximal tubule cells.ConclusionChronic nicotine exposure incites higher oxidative stress in the adolescent than in adult kidney because of a pre-existent pro-oxidant milieu.

Formaldehyde (HCHO) directly affects the atmospheric oxidative capacity through its effects on HOx. In remote marine environments, such as the tropical western Pacific (TWP), it is particularly important to understand the processes controlling the abundance of HCHO because model output from these regions is used to correct satellite retrievals of HCHO. Here we have used observations from the Convective Transport of Active Species in the Tropics (CONTRAST) field campaign, conducted during January and February 2014, to evaluate our understanding of the processes controlling the distribution of HCHO in the TWP as well as its representation in chemical transport/climate models. Observed HCHO mixing ratios varied from ~500 parts per trillion by volume (pptv) near the surface to ~75 pptv in the upper troposphere. Recent convective transport of near surface HCHO and its precursors, acetaldehyde and possibly methyl hydroperoxide, increased upper tropospheric HCHO mixing ratios by ~33% (22 pptv); this air contained roughly 60% less NO than more aged air. Output from the CAM‐Chem chemistry transport model (2014 meteorology) as well as nine chemistry climate models from the Chemistry‐Climate Model Initiative (free‐running meteorology) are found to uniformly underestimate HCHO columns derived from in situ observations by between 4 and 50%. This underestimate of HCHO likely results from a near factor of two underestimate of NO in most models, which strongly suggests errors in NOxemissions inventories and/or in the model chemical mechanisms. Likewise, the lack of oceanic acetaldehyde emissions and potential errors in the model acetaldehyde chemistry lead to additional underestimates in modeled HCHO of up to 75 pptv (~15%) in the lower troposphere. Global chemistry climate models (CCMs) underestimate observed HCHO in the tropical western Pacific troposphere during CONTRAST by between 4 and 50%Errors in NOxchemistry and emissions are significant drivers of the measurement versus model discrepancy for HCHO in the CCMsLack of oceanic emissions and missing in situ production of acetaldehyde leads to additional global chemistry model underestimates of HCHO

Clouds play a critical role in modulating tropospheric radiation and thus photochemistry. We develop a methodology for calculating the vertical distribution of tropospheric ultraviolet (300–420 nm) actinic fluxes using satellite cloud retrievals and a radiative transfer model. We demonstrate that our approach can accurately reproduce airborne‐measured actinic fluxes from the 2013 Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS) campaign as a case study. The results show that the actinic flux is reduced below moderately thick clouds with increasing cloud optical depth and can be enhanced by a factor of 2 above clouds. Inside clouds, the actinic flux can be enhanced by up to 2.4 times in the upper part of clouds or reduced up to 10 times in the lower parts of clouds. Our study suggests that the use of satellite‐derived actinic fluxes as input to chemistry‐transport models can improve the accuracy of photochemistry calculations. Satellite cloud retrievals are used in a radiative transfer model to simulate cloudy‐sky actinic flux in the U.S.Clouds significantly attenuate and/or enhance actinic fluxes relative to cloud‐free skiesSatellite‐constrained actinic fluxes capture well in situ airborne measurements from SEAC4RS where cloud‐sky conditions represent more than 60% of the total data

Gas‐phase volatile organic compounds (VOCs) were measured at three vertical levels between 0.6 m and 5.4 m in the Arctic boundary layer in Barrow, Alaska, for the Ocean‐Atmosphere‐Sea Ice‐Snowpack (OASIS)‐2009 field campaign during March–April 2009. C4‐C8nonmethane hydrocarbons (NMHCs) and oxygenated VOCs (OVOCs), including alcohols, aldehydes, and ketones, were quantified multiple times per hour, day and night, during the campaign using in situ fast gas chromatography‐mass spectrometry. Three canister samples were also collected daily and subsequently analyzed for C2‐C5NMHCs. The NMHCs and aldehydes demonstrated an overall decrease in mixing ratios during the experiment, whereas acetone and 2‐butanone showed increases. Calculations of time‐integrated concentrations of Br atoms, ∫[Br]dt, yielded values as high as (1.34 ± 0.27) × 1014cm−3s during the longest observed ozone depletion event (ODE) of the campaign and were correlated with the steady state Br calculated at the site during this time. Both chlorine and bromine chemistry contributed to the large perturbations on the production and losses of VOCs. Notably, acetaldehyde, propanal, and butanal mixing ratios dropped below the detection limit of the instrument (3 parts per trillion by volume (pptv) for acetaldehyde and propanal, 2 pptv for butanal) during several ODEs due to Br chemistry. Chemical flux calculations of OVOC production and loss are consistent with localized high Cl‐atom concentrations either regionally or within a very shallow surface layer, while the deeper Arctic boundary layer provides a continuous source of precursor alkanes to maintain the OVOC mixing ratios. Integrated Cl and Br atom concentrations calculated from NMHC are decoupledStrong positive correlation observed between ozone and aldehyde depletion eventsAlkane‐Cl reactions play a key role in OVOC chemical fluxes in the Arctic

We use a 0‐D photochemical box model and a 3‐D global chemistry‐climate model, combined with observations from the NOAA Southeast Nexus (SENEX) aircraft campaign, to understand the sources and sinks of glyoxal over the Southeast United States. Box model simulations suggest a large difference in glyoxal production among three isoprene oxidation mechanisms (AM3ST, AM3B, and Master Chemical Mechanism (MCM) v3.3.1). These mechanisms are then implemented into a 3‐D global chemistry‐climate model. Comparison with field observations shows that the average vertical profile of glyoxal is best reproduced by AM3ST with an effective reactive uptake coefficient γglyxof 2 × 10−3and AM3B without heterogeneous loss of glyoxal. The two mechanisms lead to 0–0.8 µg m−3secondary organic aerosol (SOA) from glyoxal in the boundary layer of the Southeast U.S. in summer. We consider this to be the lower limit for the contribution of glyoxal to SOA, as other sources of glyoxal other than isoprene are not included in our model. In addition, we find that AM3B shows better agreement on both formaldehyde and the correlation between glyoxal and formaldehyde (RGF= [GLYX]/[HCHO]), resulting from the suppression of δ‐isoprene peroxy radicals. We also find that MCM v3.3.1 may underestimate glyoxal production from isoprene oxidation, in part due to an underestimated yield from the reaction of isoprene epoxydiol (IEPOX) peroxy radicals with HO2. Our work highlights that the gas‐phase production of glyoxal represents a large uncertainty in quantifying its contribution to SOA. Box model‐simulated glyoxal production from three isoprene oxidation mechanisms differ greatlyAerosol uptake of glyoxal was constrained using airborne in situ measurements and a global modelModel results show that glyoxal contributes 0–14% of SOA in the Southeast U.S. during summer

Tropospheric O3has been decreasing across much of the eastern U.S. but has remained steady or even increased in some western regions. Recent increases in VOC and NOxemissions associated with the production of oil and natural gas (O&NG) may contribute to this trend in some areas. The Northern Front Range of Colorado has regularly exceeded O3air quality standards during summertime in recent years. This region has VOC emissions from a rapidly developing O&NG basin and low concentrations of biogenic VOC in close proximity to urban‐Denver NOxemissions. Here VOC OH reactivity (OHR), O3production efficiency (OPE), and an observationally constrained box model are used to quantify the influence of O&NG emissions on regional summertime O3production. Analyses are based on measurements acquired over two summers at a central location within the Northern Front Range that lies between major regional O&NG and urban emission sectors. Observational analyses suggest that mixing obscures any OPE differences in air primarily influenced by O&NG or urban emission sector. The box model confirms relatively modest OPE differences that are within the uncertainties of the field observations. Box model results also indicate that maximum O3at the measurement location is sensitive to changes in NOxmixing ratio but also responsive to O&NG VOC reductions. Combined, these analyses show that O&NG alkanes contribute over 80% to the observed carbon mixing ratio, roughly 50% to the regional VOC OHR, and approximately 20% to regional photochemical O3production. Modeled photochemical O3production is Nox‐sensitive at a central location in the Colorado Northern Front RangeOil and natural gas VOC emissions contribute over 80% to the observed carbon mixing ratio and 17.4% to maximum modeled photochemical O3Observed O3production efficiencies are variable but show an influence of less than 1.8 ppbv/ppbv from oil and natural gas VOC emissions

Background:Statins elicit antioxidant effects independently of their lipid-lowering properties. Heme oxygenase-1 (HO-1) induction may be a part of these pleiotropic effects, which are insufficiently described in the kidney. We hypothesize that simvastatin (SIM) transcriptionally activates HO-1 that protects renal proximal tubule cells from lipotoxic injury.Methods:Impact of SIM on 100 µmol/l oleic acid (OA)-mediated reactive oxygen species (ROS) production and consequent oxidative stress (4-hydroxynonenal (HNE) content) as well as cell injury/apoptosis (lactate dehydrogenase (LDH) release, caspase-3 activation) were determined in cultured renal proximal tubule (NRK52E) cells. Effect of SIM on the HO-1 promoter and its enhancer elements (antioxidant response element (ARE), CCAAT, AP1, and cAMP response element (CRE)) was also determined in reporter luciferase assays. Dominant-negative (dnMEK, M1CREB) and pharmacologic (H89) approaches were used to inhibit activation of extracellular signal regulated kinase (ERK), CREB, and protein kinase A (PKA), respectively.Results:SIM dose-dependently activated the HO-1 promoter that was essential for protection against OA-dependent ROS production/oxidative stress and LDH release/caspase-3 activation. We found that the HO-1 promoter was induced through ERK and PKA-dependent activation of the CRE by SIM.Conclusion:SIM may protect the kidney from adverse effects of circulating fatty acids by upregulating the antioxidant HO-1, aside from its well-described lipid-lowering effects.

The National Pipeline Mapping System (NPMS) is a geographic information system (GIS) created by the US Department of Transportation, Office of Pipeline Safety (OPS) in cooperation with other federal and [...]

Nitrous acid (HONO) mixing ratios measured in aged wildfire smoke plumes were higher than expected from known homogeneous chemical reactions. In a representative smoke plume, intercepted hours to days downwind of the source, the missing HONO source was highly correlated to particulate nitrate photolysis and NO2reactive uptake to particles. Using a multilinear regression involving these two sources, we could explain the missing HONO production in this plume (R2= 0.77). The resulting fit parameters from this plume had good explanatory power (R2= 0.64) for missing HONO production in other fire plumes. The mean enhancement factor for particulate nitrate photolysis relative to gas‐phase nitric acid photolysis was 63 and the mean NO2reactive uptake coefficient to submicron aerosol surface area forming HONO was 4.9 × 10−4. Given the likelihood of other neglected secondary HONO sources, these values are upper‐limits, suggesting a need to revisit HONO formation mechanisms in aged wildfire smoke. A river of smoke from multiple wildfires was sampled far downwind and served as a natural laboratory for evaluating sources of nitrous acid (HONO) in aged wildfire smoke. HONO photolysis is an important source of reactive oxidants that initiate chemical transformations of wildfire emissions. We demonstrate that sources of HONO from chemical processes, known as secondary HONO sources, can largely be explained by two processes – the photolysis of particulate nitrate and the reactive uptake of nitrogen dioxide (NO2) to smoke aerosol particles. High time resolution in situ observations of HONO and auxiliary measurements were used to map out variations in the missing HONO source across a wide span of wildfire characteristics. The results place an upper limit on the magnitude of HONO sources from particulate nitrate photolysis, and suggest that the heterogeneous NO2reactive uptake to smoke particles could be more important than previous field studies have indicated. These findings demonstrate the existence of additional processes other than direct emissions responsible for HONO formation in fire smoke. This secondary HONO source could increase the oxidizing capacity of wildfire smoke plumes significantly downwind of the emission source and therefore affect the formation and lifetime of other secondary wildfire smoke components. Secondary multi‐phase processes dominate daytime HONO levels in aged (>3 hr) fire smokeThe inferred strength of secondary HONO production is most correlated to NO2, aerosol surface area, and particulate nitrateWe find significantly weaker HONO formation from particulate nitrate photolysis than previous reports Secondary multi‐phase processes dominate daytime HONO levels in aged (>3 hr) fire smoke The inferred strength of secondary HONO production is most correlated to NO2, aerosol surface area, and particulate nitrate We find significantly weaker HONO formation from particulate nitrate photolysis than previous reports

Chlorine radicals can function as a strong atmospheric oxidant, particularly in polar regions, where levels of hydroxyl radicals are low. In the atmosphere, chlorine radicals expedite the degradation of methane and tropospheric ozone, and the oxidation of mercury to more toxic forms. Here we present direct measurements of molecular chlorine levels in the Arctic marine boundary layer in Barrow, Alaska, collected in the spring of 2009 over a six-week period using chemical ionization mass spectrometry. We report high levels of molecular chlorine, of up to 400 pptv. Concentrations peaked in the early morning and late afternoon, and fell to near-zero levels at night. Average daytime molecular chlorine levels were correlated with ozone concentrations, suggesting that sunlight and ozone are required for molecular chlorine formation. Using a time-dependent box model, we estimate that the chlorine radicals produced from the photolysis of molecular chlorine oxidized more methane than hydroxyl radicals, on average, and enhanced the abundance of short-lived peroxy radicals. Elevated hydroperoxyl radical levels, in turn, promoted the formation of hypobromous acid, which catalyses mercury oxidation and the breakdown of tropospheric ozone. We therefore suggest that molecular chlorine exerts a significant effect on the atmospheric chemistry of the Arctic.

Nitrogen oxides are essential for the formation of secondary atmospheric aerosols and of atmospheric oxidants such as ozone and the hydroxyl radical, which controls the self-cleansing capacity of the atmosphere. Nitric acid, a major oxidation product of nitrogen oxides, has traditionally been considered to be a permanent sink of nitrogen oxides. However, model studies predict higher ratios of nitric acid to nitrogen oxides in the troposphere than are observed. A ‘renoxification’ process that recycles nitric acid into nitrogen oxides has been proposed to reconcile observations with model studies, but the mechanisms responsible for this process remain uncertain. Here we present data from an aircraft measurement campaign over the North Atlantic Ocean and find evidence for rapid recycling of nitric acid to nitrous acid and nitrogen oxides in the clean marine boundary layer via particulate nitrate photolysis. Laboratory experiments further demonstrate the photolysis of particulate nitrate collected on filters at a rate more than two orders of magnitude greater than that of gaseous nitric acid, with nitrous acid as the main product. Box model calculations based on the Master Chemical Mechanism suggest that particulate nitrate photolysis mainly sustains the observed levels of nitrous acid and nitrogen oxides at midday under typical marine boundary layer conditions. Given that oceans account for more than 70 per cent of Earth’s surface, we propose that particulate nitrate photolysis could be a substantial tropospheric nitrogen oxide source. Recycling of nitrogen oxides in remote oceanic regions with minimal direct nitrogen oxide emissions could increase the formation of tropospheric oxidants and secondary atmospheric aerosols on a global scale.

As part of a screening study, a literature review, personal interviews, and field work at several deployment locations, we examined the historical use of biological warfare agents and the vulnerability of food at military deployment locations to bioterrorist attack. The results of our experience suggest the following: historically, food has occasionally been used as a weapon by individuals; a benchmark procedure already exists to evaluate and ensure the safety of foods procured and used by the U.S. federal government; and food sources at the deployment locations examined are vulnerable to terrorist attack as determined by a critical control point analysis. Recommendations to potentially decrease the vulnerability of the U.S. military food supply to intentional contamination are also provided.

Reactive chlorine and bromine species emitted from snow and aerosols can significantly alter the oxidative capacity of the polar boundary layer. However, halogen production mechanisms from snow remain highly uncertain, making it difficult for most models to include descriptions of halogen snow emissions and to understand the impact on atmospheric chemistry. We investigate the influence of Arctic halogen emissions from snow on boundary layer oxidation processes using a one‐dimensional atmospheric chemistry and transport model (PACT‐1D). To understand the combined impact of snow emissions and boundary layer dynamics on atmospheric chemistry, we model Cl2and Br2primary emissions from snow and include heterogeneous recycling of halogens on both snow and aerosols. We focus on a 2‐day case study from the 2009 Ocean‐Atmosphere‐Sea Ice‐Snowpack campaign at Utqiaġvik, Alaska. The model reproduces both the diurnal cycle and high quantity of Cl2observed, along with the measured concentrations of Br2, BrO, and HOBr. Due to the combined effects of emissions, recycling, vertical mixing, and atmospheric chemistry, reactive chlorine is typically confined to the lowest 15 m of the atmosphere, while bromine can impact chemistry up to and above the surface inversion height. Upon including halogen emissions and recycling, the concentration of HOx(HOx= OH + HO2) at the surface increases by as much as a factor of 30 at mid‐day. The change in HOxdue to halogen chemistry, as well as chlorine atoms derived from snow emissions, significantly reduce volatile organic compound lifetimes within a shallow layer near the surface. A combination of factors including snow emissions, vertical mixing, and atmospheric chemistry explain surface Arctic halogen observationsSnow emissions of halogens impact atmospheric chemistry within a shallow layer near the surfaceSurface HOxconcentrations are increased by up to a factor of 30 due to halogen chemistry A combination of factors including snow emissions, vertical mixing, and atmospheric chemistry explain surface Arctic halogen observations Snow emissions of halogens impact atmospheric chemistry within a shallow layer near the surface Surface HOxconcentrations are increased by up to a factor of 30 due to halogen chemistry

Wildfire emissions affect downwind air quality and human health. Predictions of these impacts using models are limited by uncertainties in emissions and chemical evolution of smoke plumes. Using high‐time‐resolution aircraft measurements, we illustrate spatial variations that can exist within a plume due to differences in the photochemical environment. Horizontal and vertical crosswind gradients of dilution‐corrected mixing ratios were observed in midday plumes for reactive compounds and their oxidation products, such as nitrous acid, catechol, and ozone, likely due to faster photochemistry in optically thinner plume edges relative to darker plume cores. Gradients in plumes emitted close to sunset are characterized by titration of O3in the plume and reduced or no gradient formation. We show how crosswind gradients can lead to underestimated emission ratios for reactive compounds and overestimated emission ratios for oxidation products. These observations will lead to improved predictions of wildfire emissions, evolution, and impacts across daytime and nighttime. Wildfire emissions have large impacts on air quality and health in downwind communities. Previous research has shown that chemical reactions in fire plumes can be remarkably fast, which modifies the impact the smoke has downwind. In this work, we show how this chemistry happens faster on the edges versus the core of plumes emitted during midday. For plumes emitted near or after sunset, oxidation chemistry generally slows and remains nearly uniform across the plume. These variations in plume chemistry will impact how plumes are modeled, and how well we can predict downwind air quality impacts. Spatial gradients are observed in dilution‐corrected mixing ratios of nitrous acid, ozone, and reactive organics in fresh wildfire plumesGradients evolve with time of day, as intensity of chemical aging varies relative to plume transport and mixingGradients should be considered when comparing plume models with measurements and estimating fire emissions from in situ observations Spatial gradients are observed in dilution‐corrected mixing ratios of nitrous acid, ozone, and reactive organics in fresh wildfire plumes Gradients evolve with time of day, as intensity of chemical aging varies relative to plume transport and mixing Gradients should be considered when comparing plume models with measurements and estimating fire emissions from in situ observations

Eighteen employees with lower respiratory symptoms later confirmed to be occupational asthma were referred for evaluation. All were employees of a single wood products plant using heated methylene diphenyl diisocyanate (MDI) in the manufacture of a synthetic wood product. Of the 18, 15 had no prior airway symptoms or other known bronchial injury, and 16 had positive methacholine bronchial provocation tests. All cases occurred during a 2.5-year period after exposure to a new manufacturing process using steam-heated MDI resin in a new manufacturing facility. Initially, employees developed symptoms related to the start-up process in the plant, with possible higher MDI exposures and probable higher resin temperatures. Later, most employees who developed new symptoms worked in areas of the plant where they were exposed mostly to heated boards. This suggests MDI sensitization arising at lower temperatures than previously considered likely for this substance. Am. J. Ind. Med. 31:56–63. © 1997 Wiley-Liss, Inc.

To gain more information about the role of tympanostomy tubes in the treatment of chronic middle ear effusion, the authors conducted a randomized trial that clearly indicated the short-term advantages of combining the insertion of an Armstrong ventilator tube with paracentesis and fluid aspiration over paracentesis and aspiration alone. A retrospective study of the success rate with three types of tympanostomy tubes (Shepard, Armstrong, and Paparella) was also carried out. The Armstrong tube had the highest success rate.

Two methods of reinnervation, the neuromuscular pedicle (NMP) and the nerve implant (NI), were compared in a model using the rabbit's denervated mentalis muscle. Results from evoked electromyographic (EMG) and muscle tension studies (twitch and tetanic contraction) provided the basis of comparison. In addition, the timing of denervation was studied (ie, at the time of implantation of the NMP or NI, or 2 weeks following implantation). The NMP achieved more rapid reinnervation and produced stronger contractions than the NI. Demonstrable reinnervation with an NMP was accelerated when the implantation occurred prior to the denervation. This was not the case with the NI. There was poor correlation between the evoked EMG potential and the strength of both twitch and tetanic contraction. It was concluded on the basis of this study that muscle tension provided a more accurate means of assessing reinnervated muscle function. Of the two methods, the NMP would seem, therefore, to be the technique of choice when it is available. The NI is certainly effective and should be used when a satisfactory NMP is not available.

Cases of cystic pituitary glands have been found in young beef and dairy cattle either suffering from vitamin A deficiency or with a history of early severe vitamin A depletion. The cysts occurred either in the residual lumen or within the posterior lobe, often causing compression of the gland and injury to the glandular parenchyma. No evidence of repair in a cystic pituitary was found in an animal that was vitamin A deficient early in life but later fed adequate amounts of carotene, suggesting that the injury of the gland may be permanent.

Wildland fires involve complicated processes that are challenging to represent in chemical transport models. Recent airborne measurements reveal remarkable chemical tomography in fresh wildland fire plumes, which remain yet to be fully explored using models. Here, we present a high‐resolution large eddy simulation model coupled to chemistry to study the chemical evolution in fresh wildland fire plume. The model is configured for a large fire heavily sampled during the Fire Influence on Regional to Global Environments and Air Quality field campaign, and a variety of airborne measurements are used to evaluate the chemical heterogeneity revealed by the model. We show that the model captures the observed cross‐transect variations of a number of compounds quite well, including ozone (O3), nitrous acid (HONO), and peroxyacetyl nitrate. The combined observational and modeling results suggest that the top and edges of fresh plume drive the photochemistry, while dark chemistry is also present but in the lower part of the plume. The model spatial resolution is shown to be very important as it may shift the chemical regime, leading to biases in O3and NOxchemistry. Based on findings in this work, we speculate that the impact of small fires on air quality may be largely underestimated in models with coarse spatial resolutions. Recent fire seasons in the United States have been record‐setting for many states. Several large wildfires raged across the entire west coast and lofted smoke plumes spread to the majority of the continental U.S. From a scientific perspective, wildland fires are fascinating due to their complexity. Fires emit heat, creating a plume of hot and turbulent air. The fire plume also contains many gases and aerosol particles produced from the burning and baking of a variety of fuels on the ground (trees, grasses, leaf litter and other fallen debris, etc.). Many of these gases and aerosol particles can impact climate, air quality, and human health. For this reason, most modern air quality and climate models now consider wildland fires. However, wildland fires are fundamentally challenging for these models, because many fine‐scale and large‐scale processes are entangled at the same time. In this work, we use a high‐resolution turbulence‐resolving numerical model to study the fine details in a wildland fire plume, with implications for large‐scale air quality and climate models. Photochemistry is active at the edges of thick fire plumes, while dark chemistry is present in the lower part and below thick plumesHydroxyl radicals formed from nitrous acid drive the plume oxidation; nitrous acid may be produced on aerosolsModel resolution affects chemistry; sufficiently high spatial resolution is needed to capture the impacts of wildfires on air quality Photochemistry is active at the edges of thick fire plumes, while dark chemistry is present in the lower part and below thick plumes Hydroxyl radicals formed from nitrous acid drive the plume oxidation; nitrous acid may be produced on aerosols Model resolution affects chemistry; sufficiently high spatial resolution is needed to capture the impacts of wildfires on air quality

This study investigates the use of airborne in situ measurements to derive transit time distributions (TTD) from the boundary layer (BL) to the upper troposphere (UT) over the highly convective tropical western Pacific (TWP). The feasibility of this method is demonstrated using 42 volatile organic compounds (VOCs) measured during the Convective Transport of Active Species in the Tropics (CONTRAST) experiment. Two important approximations necessary for the application are the constant chemical lifetimes for each compound and the representation of the BL source by the local CONTRAST data. To characterize uncertainties associated with the first approximation, we quantify the changes in derived TTDs when chemical lifetimes are estimated using conditions of the BL, UT, and tropospheric average. With the support of a trajectory model study in a companion paper, we characterize the BL source region contributing to the transport to the sampled UT. In addition to the TTDs derived using a regional average, we analyze the potential information content in locally averaged measurements to represent the dynamical variability of the region. Around 150 TTDs, derived using measurements on a ∼100 km spatial scale, show a distribution of mean and mode transit times consistent with the wide range of convective conditions encountered during the campaign. Two extreme cases, with the shortest and the near‐longest TTD, are examined using the dynamical background of the measurements and back trajectory analyses. The result provides physical consistency supporting the hypothesis that sufficient information can be obtained from measurements to resolve dynamical variability of the region. In this study, we use measurements of the atmospheric chemical composition to derive vertical transport timescales over the tropical western Pacific, where convective processes dominate. A large suite of trace gases with a wide range of chemical lifetimes are measured from a research aircraft. The trace gas measurements are used to construct “transit time distributions,” which capture the relative contributions of various transport pathways to the chemical composition of the upper troposphere in the study region. Results highlight the wealth of information in atmospheric chemical composition measurements, which is important not only for understanding chemistry of the atmosphere but also for quantifying aspects of atmospheric dynamics and circulation. The approximations and uncertainties in deriving airborne chemical observation‐based tropospheric transit time distributions are examinedThe necessary approximation of trace gas lifetimes is found to be the largest source of uncertaintyThe method successfully identified a range of dynamical transport variability from aircraft measurements The approximations and uncertainties in deriving airborne chemical observation‐based tropospheric transit time distributions are examined The necessary approximation of trace gas lifetimes is found to be the largest source of uncertainty The method successfully identified a range of dynamical transport variability from aircraft measurements

Awake craniotomy is widely used for surgery in eloquent brain in order to facilitate maximal safe resection of brain tumours. There has been huge progress in both surgical and anaesthetic techniques used during awake craniotomy. This study reports a single surgeon experience of awake craniotomy for tumour resection over a 14 year period focusing on the safety and feasibility of a simple technique.

The Western Wildfire Experiment for Cloud Chemistry, Aerosol Absorption, and Nitrogen (WE‐CAN) deployed the NSF/NCAR C‐130 aircraft in summer 2018 across the western U.S. to sample wildfire smoke during its first days of atmospheric evolution. We present a summary of a subset of reactive oxidized nitrogen species (NOy) in plumes sampled in a pseudo‐Lagrangian fashion. Emissions of nitrogen oxides (NOx= NO + NO2) and nitrous acid (HONO) are rapidly converted to more oxidized forms. Within 4 h, ∼86% of the ΣNOyis in the form of peroxy acyl nitrates (PANs) (∼37%), particulate nitrate (pNO3) (∼27%), and gas‐phase organic nitrates (Org N(g)) (∼23%). The average e‐folding time and distance for NOxare ∼90 min and ∼40 km, respectively. Nearly no enhancements in nitric acid (HNO3) were observed in plumes sampled in a pseudo‐Lagrangian fashion, implying HNO3‐limited ammonium nitrate (NH4NO3) formation, with one notable exception that we highlight as a case study. We also summarize the observed partitioning of NOyin all the smoke samples intercepted during WE‐CAN. In smoke samples intercepted above 3 km above sea level (ASL), the contributions of PANs and pNO3to ΣNOyincrease with altitude. WE‐CAN also sampled smoke from multiple fires mixed with anthropogenic emissions over the California Central Valley. We distinguish samples where anthropogenic NOxemissions appear to lead to an increase in NOxabundances by a factor of four and contribute to additional PAN formation. NOxand HONO are rapidly converted to other species. The average e‐folding time (distance) for NOxis ∼90 min (∼40 km)In 4 h, PANs contribute ∼37% of the ΣNOyspecies in smoke; pNO3is the second largest (∼27%) contributorIn 4 h, Org N(g)constitute a large portion (∼23%) of the ΣNOyin the plumes sample during WE‐CAN NOxand HONO are rapidly converted to other species. The average e‐folding time (distance) for NOxis ∼90 min (∼40 km) In 4 h, PANs contribute ∼37% of the ΣNOyspecies in smoke; pNO3is the second largest (∼27%) contributor In 4 h, Org N(g)constitute a large portion (∼23%) of the ΣNOyin the plumes sample during WE‐CAN

We present a novel method, the Gaussian observational model for edge to center heterogeneity (GOMECH), to quantify the horizontal chemical structure of plumes. GOMECH fits observations of short-lived emissions or products against a long-lived tracer (e.g., CO) to provide relative metrics for the plume width (wi/wCO) and center (bi/wCO). To validate GOMECH, we investigate OH and NO3oxidation processes in smoke plumes sampled during FIREX-AQ (Fire Influence on Regional to Global Environments and Air Quality, a 2019 wildfire smoke study). An analysis of 430 crosswind transects demonstrates that nitrous acid (HONO), a primary source of OH, is narrower than CO (wHONO/wCO= 0.73–0.84 ± 0.01) and maleic anhydride (an OH oxidation product) is enhanced on plume edges (wmaleicanhydride/wCO= 1.06–1.12 ± 0.01). By contrast, NO3production [P(NO3)] occurs mainly at the plume center (wP(NO3)/wCO= 0.91–1.00 ± 0.01). Phenolic emissions, highly reactive to OH and NO3, are narrower than CO (wphenol/wCO= 0.96 ± 0.03, wcatechol/wCO= 0.91 ± 0.01, and wmethylcatechol/wCO= 0.84 ± 0.01), suggesting that plume edge phenolic losses are the greatest. Yet, nitrophenolic aerosol, their oxidation product, is the greatest at the plume center (wnitrophenolicaerosol/wCO= 0.95 ± 0.02). In a large plume case study, GOMECH suggests that nitrocatechol aerosol is most associated with P(NO3). Last, we corroborate GOMECH with a large eddy simulation model which suggests most (55%) of nitrocatechol is produced through NO3in our case study.

Acetone is one of the most abundant oxygenated volatile organic compounds (VOCs) in the atmosphere. The oceans impose a strong control on atmospheric acetone, yet the oceanic fluxes of acetone remain poorly constrained. In this work, the global budget of acetone is evaluated using two global models: CAM‐chem and GEOS‐Chem. CAM‐chem uses an online air‐sea exchange framework to calculate the bidirectional oceanic acetone fluxes, which is coupled to a data‐oriented machine‐learning approach. The machine‐learning algorithm is trained using a global suite of seawater acetone measurements. GEOS‐Chem uses a fixed surface seawater concentration of acetone to calculate the oceanic fluxes. Both model simulations are compared to airborne observations from a recent global‐scale, multiseasonal campaign, the NASA Atmospheric Tomography Mission (ATom). We find that both CAM‐chem and GEOS‐Chem capture the measured acetone vertical distributions in the remote atmosphere reasonably well. The combined observational and modeling analysis suggests that (i) the ocean strongly regulates the atmospheric budget of acetone. The tropical and subtropical oceans are mostly a net source of acetone, while the high‐latitude oceans are a net sink. (ii) CMIP6 anthropogenic emission inventory may underestimate acetone and/or its precursors in the Northern Hemisphere. (iii) The MEGAN biogenic emissions model may overestimate acetone and/or its precursors, and/or the biogenic oxidation mechanisms may overestimate the acetone yields. (iv) The models consistently overestimate acetone in the upper troposphere‐lower stratosphere over the Southern Ocean in austral winter. (v) Acetone contributes up to 30–40% of hydroxyl radical production in the tropical upper troposphere/lower stratosphere. Acetone is widely observed in the Earth's atmosphere, with mixing ratios ranging from parts‐per‐trillion levels in the stratosphere to parts‐per‐billion levels in polluted regions. Acetone is directly emitted from a wide variety of natural and anthropogenic sources and is also produced from the photochemical oxidation of a number of precursors. The role of the ocean is complicated; acetone is produced in the ocean from the photolysis of colored dissolved organic materials or from biological processes but is also removed via microbial uptake. Previous studies have found that the direction and magnitude of oceanic acetone fluxes vary dramatically with seasons and locations. In this work, we use a data‐oriented machine‐learning approach to predict the surface seawater concentration of acetone, leveraging in situ acetone measurements in the surface seawater around the globe. This machine learning‐based approach shows promising potential and can be expanded to the bottom‐up oceanic emissions of other climate‐relevant compounds. We develop an online air‐sea exchange module for acetone, with ocean biogeochemistry represented using data‐oriented machine learningTwo separate global acetone simulations are compared to global‐scale multiseasonal airborne observationsGlobal models consistently overestimate acetone in the upper troposphere over the Southern Ocean in austral winter

Peritonsillar abscess formation is an uncommon complication of infectious mononucleosis (IM). Early case reports implicated corticosteroids in the development of such abscesses, however, subsequent studies suggested that these drugs do not promote the formation of abscesses at several sites outside the central nervous system. It has recently been demonstrated that zwitterionic polysaccharides, in bacterial capsules, form complexes with CD4+ T lymphocytes leading to abscess formation. A patient is presented who developed peritonsillar abscess a few days after initiation of corticosteroid therapy for IM; the medical literature was reviewed in respect of this subject. It appears that the occurrence of these abscesses in IM is not strongly linked to corticosteroid treatment. The authors, therefore, recommend that steroids should not be withheld from patients with severe IM on the basis that they may precipitate the development of peritonsillar abscess.

Convective transport from the marine boundary layer to the upper troposphere (UT) is investigated using airborne in situ measurements of chemical species over the tropical western Pacific. Using 42 volatile organic compounds with photochemical lifetimes ranging from shorter than a day to multiple decades, we derive a transit time spectrum G(t)and the associated modal and mean transit times for the UT air mass over the convectively dominant tropical western Pacific region. G(t)describes relative contributions of air masses transported from the marine boundary layer to the UT via all transport paths with different transit times. We further demonstrate that the volatile organic compound‐derived transit time scale is broadly comparable to that estimated from convective mass flux. The observation‐based transit time spectrum not only provides insights into convective transport pathways, but also has the potential to serve as an effective diagnostic for evaluating the representation of convective transport in global models. Tropical deep convection is an important mechanism whereby air mass and chemical species are transported from near the surface to the upper troposphere and lower stratosphere. This transport process is difficult to quantify by observations or represent in models because of the small spatial scales and short temporal scales involved. In this study, we present a method to characterize convective transport using the framework of transit time spectrum, which describes the relative contributions of different transport paths with different transit times. We demonstrate that convective transport transit time spectrum can be derived using airborne in situ measurements of chemical species with a wide range of lifetimes, and we illustrate the wealth of information they provide for quantifying transport processes. This analysis method has the potential to serve as a unique diagnostic for evaluating the representation of convective transport in global models. Airborne in situ measurements of VOCs with a wide range of lifetimes are used to quantify a convective‐transport transit time spectrumThe transit time scale derived from VOC measurements is broadly comparable to that estimated from convective mass fluxThe estimated transit time spectrum has the potential to serve as an effective diagnostic for evaluating convective transport in CCMs