Human galectins have distinct and overlapping biological roles in immunological homeostasis. However, the underlying differences among galectins in glycan binding specificity regulating these ...functions are unclear. Galectin-8 (Gal-8), a tandem repeat galectin, has two distinct carbohydrate recognition domains (CRDs) that may cross-link cell surface counter receptors. Here we report that each Gal-8 CRD has differential glycan binding specificity and that cell signaling activity resides in the C-terminal CRD. Full-length Gal-8 and recombinant individual domains (Gal-8N and Gal-8C) bound to human HL60 cells, but only full-length Gal-8 signaled phosphatidylserine (PS) exposure in cells, which occurred independently of apoptosis. Although desialylation of cells did not alter Gal-8 binding, it enhanced cellular sensitivity to Gal-8-induced PS exposure. By contrast, HL60 cell desialylation increased binding by Gal-8C but reduced Gal-8N binding. Enzymatic reduction in surface poly-N-acetyllactosamine (polyLacNAc) glycans in HL60 cells reduced cell surface binding by Gal-8C but did not alter Gal-8N binding. Cross-linking and light scattering studies showed that Gal-8 is dimeric, and studies on individual subunits indicate that dimerization occurs through the Gal-8N domain. Mutations of individual domains within full-length Gal-8 showed that signaling activity toward HL60 cells resides in the C-terminal domain. In glycan microarray analyses, each CRD of Gal-8 showed different binding, with Gal-8N recognizing sulfated and sialylated glycans and Gal-8C recognizing blood group antigens and polyLacNAc glycans. These results demonstrate that Gal-8 dimerization promotes functional bivalency of each CRD, which allows Gal-8 to signal PS exposure in leukocytes entirely through C-terminal domain recognition of polyLacNAc glycans.
Health disparities related to race, ethnicity, and socioeconomic status persist and are commonly encountered by practitioners of pediatric and adult pulmonary, critical care, and sleep medicine in ...the United States. To address such disparities and thus progress toward equality in respiratory health, the American Thoracic Society and the National Heart, Lung, and Blood Institute convened a workshop in May of 2015. The workshop participants addressed health disparities by focusing on six topics, each of which concluded with a panel discussion that proposed recommendations for research on racial, ethnic, and socioeconomic disparities in pulmonary, critical care, and sleep medicine. Such recommendations address best practices to advance research on respiratory health disparities (e.g., characterize broad ethnic groups into subgroups known to differ with regard to a disease of interest), risk factors for respiratory health disparities (e.g., study the impact of new tobacco or nicotine products on respiratory diseases in minority populations), addressing equity in access to healthcare and quality of care (e.g., conduct longitudinal studies of the impact of the Affordable Care Act on respiratory and sleep disorders), the impact of personalized medicine on disparities research (e.g., implement large studies of pharmacogenetics in minority populations), improving design and methodology for research studies in respiratory health disparities (e.g., use study designs that reduce participants' burden and foster trust by engaging participants as decision-makers), and achieving equity in the pulmonary, critical care, and sleep medicine workforce (e.g., develop and maintain robust mentoring programs for junior faculty, including local and external mentors). Addressing these research needs should advance efforts to reduce, and potentially eliminate, respiratory, sleep, and critical care disparities in the United States.
A cloud‐resolved storm and chemistry simulation of a severe convective system in Oklahoma constrained by anvil aircraft observations of NOx was used to estimate the mean production of NOx per flash ...in this storm. An upward ice flux scheme was used to parameterize flash rates in the model. Model lightning was also constrained by observed lightning flash types and the altitude distribution of flash channel segments. The best estimate of mean NOx production by lightning in this storm was 80–110 mol per flash, which is smaller than many other literature estimates. This result is likely due to the storm having been a high flash rate event in which flash extents were relatively small. Over the evolution of this storm a moderate negative correlation was found between the total flash rate and flash extent and energy per flash. A longer‐term simulation at 36‐km horizontal resolution with parameterized convection was used to simulate the downwind transport and chemistry of the anvil outflow from the same storm. Convective transport of low‐ozone air from the boundary layer decreased ozone in the anvil outflow by up to 20–40 ppbv compared with the initial conditions, which contained stratospheric influence. Photochemical ozone production in the lightning‐NOx enhanced convective plume proceeded at a rate of 10–11 ppbv per day in the 9–11 km outflow layer over the 24‐hr period of downwind transport to the Southern Appalachians. Photochemical production plays a large role in the restoration of upper tropospheric ozone following deep convection.
Plain Language Summary
Nitrogen oxides are important precursors for tropospheric ozone, an important greenhouse gas. The global amount of nitrogen oxides produced by lightning remains highly uncertain, primarily because of uncertainty in the amount produced per flash. In this paper we use an approach that involves cloud‐resolved modeling with chemistry, constrained by observed flash rates and aircraft measurements of nitrogen oxides, to make an estimate of the mean production per flash for an observed severe storm over Oklahoma. We estimate that the mean production rate was 80–110 mol per flash for this high flash rate storm, which is at the lower end of the range reported in the literature. We use a regional model to follow the outflow of the Oklahoma storm downwind to estimate the amount of ozone produced in the upper tropospheric outflow plume by the lightning‐generated nitrogen oxides. Our estimate is in the range found in previous studies, and we note that the ozone production by photochemistry is an important process in restoring upper tropospheric ozone following storms that lofted low values of ozone from the layer of air near the surface.
Key Points
Mean lightning NOx production was 80–110 mol flash−1 for a high flash rate storm, based on a model constrained by flash and NOx observations
Net O3 production in the upper outflow of a high flash rate storm was at a rate of 10–11 ppbv day−1 during 24 hr of downwind transport
Production of O3 due to lightning NOx contributed to the recovery of upper tropospheric O3 following reductions due to convective transport
Different atmospheric mercury forms have been measured at a suburban site in Beltsville, Maryland in the Mid-Atlantic United States since 2007 to investigate their inter-annual, seasonal and diurnal ...variabilities. Average concentrations and standard deviations of hourly measurements from 2007 to 2015 were 1.41 ± 0.23 ng m−3 for gaseous elemental mercury (GEM), 4.6 ± 33.7 pg m−3 for gaseous oxidized mercury (GOM), and 8.6 ± 56.8 pg m−3 for particulate-bound mercury (PBM). Observations show that on average, the rates of decrease were 0.020 ± 0.007 ng m−3 yr−1 (or 1.3 ± 0.5% yr−1, statistically significant, p-value < 0.01) for GEM, 0.54 ± 0.19 pg m−3 yr−1 (or 7.3 ± 2.6% yr−1, statistically significant, p-value < 0.01) for GOM, and 0.15 ± 0.35 pg m−3 yr−1 (or 1.6 ± 3.8% yr−1, statistically insignificant, p-value > 0.01) for PBM over this nine-year period. In addition, the collocated annual mercury wet deposition decreased at a rate of 0.51 ± 0.24 μg m−2 yr−2 (or 4.2 ± 1.9% yr−1, statistically insignificant, p-value > 0.01). Diurnal variation of GEM shows a slight peak in the morning, likely due to the shallow boundary layer. Seasonal variation of GEM shows lower levels in fall. Both diurnal variations of GOM and PBM show peaks in the afternoon likely due to the photochemical production of reactive mercury from the oxidation of GEM and the influence of boundary layer processes. Seasonally, GOM measurements show high levels in spring and constant low levels in the other three seasons, while PBM measurements exhibit higher levels from late fall to early spring and lower levels from late spring to fall. These measurement data were analyzed using the HYSPLIT back trajectory model in order to examine possible source-receptor relationships at this suburban site. Trajectory frequency analysis shows that high GEM/GOM/PBM events were generally associated with high frequencies of the trajectories passing through areas with high mercury emissions, while low GEM/GOM/PBM levels were largely associated the trajectories passing through relatively clean areas. This study indicates that local and regional sources appear to have a significant impact on the site and these impacts appear to have changed over time, as the local/regional emissions have been reduced.
•Decreases in GEM, GOM, PBM, and Hg wet deposition over 2007–2015 were observed.•Trajectory analysis shows correlation between Hg emissions and observed mercury.•Two possible sources of GOM include direct emissions and photochemical oxidation.
We examine wet scavenging of soluble trace gases in storms observed during the Deep Convective Clouds and Chemistry (DC3) field campaign. We conduct high‐resolution simulations with the Weather ...Research and Forecasting model with Chemistry (WRF‐Chem) of a severe storm in Oklahoma. The model represents well the storm location, size, and structure as compared with Next Generation Weather Radar reflectivity, and simulated CO transport is consistent with aircraft observations. Scavenging efficiencies (SEs) between inflow and outflow of soluble species are calculated from aircraft measurements and model simulations. Using a simple wet scavenging scheme, we simulate the SE of each soluble species within the error bars of the observations. The simulated SEs of all species except nitric acid (HNO3) are highly sensitive to the values specified for the fractions retained in ice when cloud water freezes. To reproduce the observations, we must assume zero ice retention for formaldehyde (CH2O) and hydrogen peroxide (H2O2) and complete retention for methyl hydrogen peroxide (CH3OOH) and sulfur dioxide (SO2), likely to compensate for the lack of aqueous chemistry in the model. We then compare scavenging efficiencies among storms that formed in Alabama and northeast Colorado and the Oklahoma storm. Significant differences in SEs are seen among storms and species. More scavenging of HNO3 and less removal of CH3OOH are seen in storms with higher maximum flash rates, an indication of more graupel mass. Graupel is associated with mixed‐phase scavenging and lightning production of nitrogen oxides (NOx), processes that may explain the observed differences in HNO3 and CH3OOH scavenging.
Key Points
Observed deep convective scavenging efficiencies simulated by simple scheme
Simulated scavenging efficiencies highly sensitive to ice retention fraction
Scavenging efficiencies vary among storms with different microphysics
Deep convective transport of surface moisture and pollution from the planetary boundary layer to the upper troposphere and lower stratosphere affects the radiation budget and climate. This study ...analyzes the deep convective transport in three different convective regimes from the 2012 Deep Convective Clouds and Chemistry field campaign: 21 May Alabama air mass thunderstorms, 29 May Oklahoma supercell severe storm, and 11 June mesoscale convective system (MCS). Lightning data assimilation within the Weather Research and Forecasting (WRF) model coupled with chemistry (WRF‐Chem) is utilized to improve the simulations of storm location, vertical structure, and chemical fields. Analysis of vertical flux divergence shows that deep convective transport in the 29 May supercell case is the strongest per unit area, while transport of boundary layer insoluble trace gases is relatively weak in the MCS and air mass cases. The weak deep convective transport in the strong MCS is unexpected and is caused by the injection into low levels of midlevel clean air by a strong rear inflow jet. In each system, the magnitude of tracer vertical transport is more closely related to the vertical distribution of mass flux density than the vertical distribution of trace gas mixing ratio. Finally, the net vertical transport is strongest in high composite reflectivity regions and dominated by upward transport.
Key Points
Lightning data assimilation improves model simulations of storm location and vertical structure
Rear inflow jets within mesoscale convective systems may weaken boundary layer trace gas vertical transport
The tracer vertical transport is more controlled by the vertical gradient of mass flux than the vertical gradient of trace gas
Deep convective transport of gaseous precursors to ozone (O3) and aerosols to the upper troposphere is affected by liquid phase and mixed‐phase scavenging, entrainment of free tropospheric air and ...aqueous chemistry. The contributions of these processes are examined using aircraft measurements obtained in storm inflow and outflow during the 2012 Deep Convective Clouds and Chemistry (DC3) experiment combined with high‐resolution (dx≤3 km) WRF‐Chem simulations of a severe storm, an air mass storm, and a mesoscale convective system (MCS). The simulation results for the MCS suggest that formaldehyde (CH2O) is not retained in ice when cloud water freezes, in agreement with previous studies of the severe storm. By analyzing WRF‐Chem trajectories, the effects of scavenging, entrainment, and aqueous chemistry on outflow mixing ratios of CH2O, methyl hydroperoxide (CH3OOH), and hydrogen peroxide (H2O2) are quantified. Liquid phase microphysical scavenging was the dominant process reducing CH2O and H2O2 outflow mixing ratios in all three storms. Aqueous chemistry did not significantly affect outflow mixing ratios of all three species. In the severe storm and MCS, the higher than expected reductions in CH3OOH mixing ratios in the storm cores were primarily due to entrainment of low‐background CH3OOH. In the air mass storm, lower CH3OOH and H2O2 scavenging efficiencies (SEs) than in the MCS were partly due to entrainment of higher background CH3OOH and H2O2. Overestimated rain and hail production in WRF‐Chem reduces the confidence in ice retention fraction values determined for the peroxides and CH2O.
Key Points
Methyl hydroperoxide mixing ratios are decreased mainly by entrainment and liquid phase and mixed‐phase scavenging
Hydrogen peroxide and formaldehyde mixing ratios affected more by liquid phase scavenging than by entrainment or aqueous chemistry
Overestimated rain/hail production in WRF‐Chem reduces confidence in ice retention fraction values determined for peroxides and formaldehyde
Abstract A cloud‐resolved storm and chemistry simulation of a severe convective system in Oklahoma constrained by anvil aircraft observations of NO x was used to estimate the mean production of NO x ...per flash in this storm. An upward ice flux scheme was used to parameterize flash rates in the model. Model lightning was also constrained by observed lightning flash types and the altitude distribution of flash channel segments. The best estimate of mean NO x production by lightning in this storm was 80–110 mol per flash, which is smaller than many other literature estimates. This result is likely due to the storm having been a high flash rate event in which flash extents were relatively small. Over the evolution of this storm a moderate negative correlation was found between the total flash rate and flash extent and energy per flash. A longer‐term simulation at 36‐km horizontal resolution with parameterized convection was used to simulate the downwind transport and chemistry of the anvil outflow from the same storm. Convective transport of low‐ozone air from the boundary layer decreased ozone in the anvil outflow by up to 20–40 ppbv compared with the initial conditions, which contained stratospheric influence. Photochemical ozone production in the lightning‐NO x enhanced convective plume proceeded at a rate of 10–11 ppbv per day in the 9–11 km outflow layer over the 24‐hr period of downwind transport to the Southern Appalachians. Photochemical production plays a large role in the restoration of upper tropospheric ozone following deep convection.
Plain Language Summary Nitrogen oxides are important precursors for tropospheric ozone, an important greenhouse gas. The global amount of nitrogen oxides produced by lightning remains highly uncertain, primarily because of uncertainty in the amount produced per flash. In this paper we use an approach that involves cloud‐resolved modeling with chemistry, constrained by observed flash rates and aircraft measurements of nitrogen oxides, to make an estimate of the mean production per flash for an observed severe storm over Oklahoma. We estimate that the mean production rate was 80–110 mol per flash for this high flash rate storm, which is at the lower end of the range reported in the literature. We use a regional model to follow the outflow of the Oklahoma storm downwind to estimate the amount of ozone produced in the upper tropospheric outflow plume by the lightning‐generated nitrogen oxides. Our estimate is in the range found in previous studies, and we note that the ozone production by photochemistry is an important process in restoring upper tropospheric ozone following storms that lofted low values of ozone from the layer of air near the surface.
Key Points Mean lightning NO x production was 80–110 mol flash −1 for a high flash rate storm, based on a model constrained by flash and NO x observations Net O 3 production in the upper outflow of a high flash rate storm was at a rate of 10–11 ppbv day −1 during 24 hr of downwind transport Production of O 3 due to lightning NO x contributed to the recovery of upper tropospheric O 3 following reductions due to convective transport
This is the most comprehensive and current reference resource on climate change available today. It features forty-nine individual chapters by some of the world's leading climate scientists. Its five ...sections address climate change in five dimensions: ecological impacts, policy analysis, international considerations, United States considerations, and mitigation options to reduce carbon emissions. In many ways, this volume supersedes the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC). Many important developments too recent to be treated in the 2007 IPCC documents are covered here. Overall, Climate Change Science and Policy paints a direr picture of the effects of climate change than do the IPCC reports. It reveals that climate change has progressed faster than the IPCC reports anticipated and that the outlook for the future is bleaker than the IPCC reported.
Workplace inhalational hazards remain common worldwide, even though they are ameliorable. Previous American Thoracic Society documents have assessed the contribution of workplace exposures to asthma ...and chronic obstructive pulmonary disease on a population level, but not to other chronic respiratory diseases. The goal of this document is to report an in-depth literature review and data synthesis of the occupational contribution to the burden of the major nonmalignant respiratory diseases, including airway diseases; interstitial fibrosis; hypersensitivity pneumonitis; other noninfectious granulomatous lung diseases, including sarcoidosis; and selected respiratory infections.
Relevant literature was identified for each respiratory condition. The occupational population attributable fraction (PAF) was estimated for those conditions for which there were sufficient population-based studies to allow pooled estimates. For the other conditions, the occupational burden of disease was estimated on the basis of attribution in case series, incidence rate ratios, or attributable fraction within an exposed group.
Workplace exposures contribute substantially to the burden of multiple chronic respiratory diseases, including asthma (PAF, 16%); chronic obstructive pulmonary disease (PAF, 14%); chronic bronchitis (PAF, 13%); idiopathic pulmonary fibrosis (PAF, 26%); hypersensitivity pneumonitis (occupational burden, 19%); other granulomatous diseases, including sarcoidosis (occupational burden, 30%); pulmonary alveolar proteinosis (occupational burden, 29%); tuberculosis (occupational burden, 2.3% in silica-exposed workers and 1% in healthcare workers); and community-acquired pneumonia in working-age adults (PAF, 10%).
Workplace exposures contribute to the burden of disease across a range of nonmalignant lung conditions in adults (in addition to the 100% burden for the classic occupational pneumoconioses). This burden has important clinical, research, and policy implications. There is a pressing need to improve clinical recognition and public health awareness of the contribution of occupational factors across a range of nonmalignant respiratory diseases.
PDF
