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Coastal regions are frequently subject to higher concentrations of ozone (O3) than areas farther inland due to thermally-direct recirculation (e.g., sea/bay breezes) of pollutants during summer months. Along with high O3 concentrations on polluted days, a bay breeze (in this case, the Chesapeake Bay breeze) causes low-level convergence over the land, which can lead to deep convection even on days without any large-scale convective forcing, altering both the local flow pattern and the concentrations and distributions of pollutants. Presented here is a bay breeze and thunderstorm climatology for Edgewood, MD, a coastal site along the Chesapeake Bay, from June, July, and August 2011–2016 between 11 and 19 EST (UTC-5). Using meteorological data from the Maryland Department of the Environment (MDE), bay breezes are identified by an automated detection algorithm, the Bay-breeze Identification Algorithm (BIA), customized for the complex coastline of river inlets within the Chesapeake Bay area. Additionally, thunderstorm vs. non-thunderstorm days are analyzed using gridded Earth Networks lightning data (ENTLN) within an influential radius of the site. The effects of bay breezes and deep convection on local O3 is quantified. The highest daily conditional mean O3 for all years was observed on bay breeze days, and the lowest on days with thunderstorms only (no bay breeze). Additionally, 39% of O3 exceedance days within the analysis time period were also bay breeze days. However, as ozone precursor emissions have fallen, the relationship between bay breezes and high O3 has diminished. While days with thunderstorms only (no bay breeze) were associated with the lowest daily mean O3, there were O3 events on some thunderstorm days, especially if there was also a bay breeze. Twenty-four percent of the total ozone exceedance days had a thunderstorm, demonstrating that thunderstorm days should not be assumed to be clean days, as boundary-layer venting and downdraft mixing depends on the thunderstorm duration and type (e.g., non-frontal/pop-up convection allowed slightly higher O3 concentrations than did frontal convection). These results illustrate the significant role that localized meteorological events that are difficult to predict play in modulating air pollution where many of the world's cities lie – near bodies of water.

The introduction of autonomous vehicles (AVs) is expected to reduce the number of road traffic accidents; however, it is expected that this will not be completely incidents free. In the event of AV incidents, ethical decisions will need to be made, e.g. a decision between colliding into an immovable rigid barrier or a group of pedestrians. Selecting the collision target of such an ethical problem involves the investigation of a model-to-decision (M2D) approach. Thus using a mathematical model of the collision scenarios to make decisions based on the severity of each outcome, e.g. minor or severe and potentially fatal injuries. In this paper, a novel nonlinear (bilinear) lumped mass-spring model of an AV colliding into an immovable rigid barrier has been developed. This model is used in conjunction with a developed pragmatic ethical decision maker (EDM) approach. This research investigates the use of such an approach for AVs (containing one or two occupants) in collision scenarios involving the choice between colliding into an immovable rigid wall or into one/ten pedestrian(s). Assuming the utility of those involved in each outcome is equal, a possible solution to the ethical problem is known as the utilitarian approach; this leads to the AV steering into the collision path of least fatalities. To gain a better understanding of the public acceptance of how an AV EDM should be programmed in the case of collisions, a survey was undertaken. The results suggest that participants of the survey support the idea of AVs steering into the collision path of least overall severity, even if the number of persons at risk is greater. The results from the M2D approach highlight the effectiveness of using such an approach on-board future AVs to minimise the severity of road traffic injuries and/or the number of fatalities.

Autonomous vehicles have the potential to improve automotive safety, largely by removing human error as a possible cause of collisions. However, it cannot be guaranteed that autonomous vehicles will be able to eliminate all collisions. Therefore, automotive safety will continue to be a necessity for automotive design. This paper proposes a decision making system which selects the least severe collision for an autonomous vehicle to take, when facing multiple imminent and unavoidable collisions on a motorway. The novel decision making system developed combines simulation results and multi-attribute decision making (MADM) methods. The simulator includes models of vehicle dynamics and the manoeuvre trajectory path. MADM methods are used to decide which vehicle(s) the autonomous vehicle should collide with, based on the severity of collisions. Severity of collisions is calculated in the simulator using the following variables: impact velocity between autonomous vehicle and vehicle ahead, impact velocity between vehicle behind and autonomous vehicle, manoeuvre acceleration and time-to-collision. Various MADM methods are investigated and three methods are selected including the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS), the Analytical Hierarchy Process (AHP), and the Analytical Network Process (ANP). Various collision scenarios are defined and tested in order to understand the impact that small changes in parameters of the autonomous vehicle and vehicles ahead and behind have on the decision made. The analysed decision making results are promising and lead to the conclusion that MADM methods can be successfully applied in autonomous vehicles.

Highly-resolved vertical profiles of ozone and reactive nitrogen in the lower troposphere were obtained using Millersville University's tethered balloon system and NASA's P-3B aircraft during the July 2011 Baltimore, MD/Washington DC and the September 2013 Houston, TX deployments of the NASA DISCOVER-AQ air quality field mission. The tethered balloon and surface measurement sites were located at Edgewood, MD and Smith Point, TX. The balloon profiles are used to connect aircraft data from the lowest portion of NASA's P-3B spirals (300 m AGL) to the surface thus creating complete profiles from the surface to 3–5 km AGL. The highest concentrations of surface ozone at these coastal sites resulted from mean flow transport of polluted air over an adjacent body of water followed by advection back over land several hours later, due to a bay or gulf breeze. Several meteorological processes including horizontal advection, vertical mixing, thermally direct circulation (i.e., bay, gulf, and, sea breezes) combined with chemical processes like photochemical production and deposition played a role in the local ozone maxima. Several small-scale, but highly polluted layers from the Chesapeake Bay advected landward over Edgewood, MD. The Houston Metro area was subject to large-scale recirculation of emissions from petrochemical sources by the Gulf of Mexico and Galveston Bay breezes.

To investigate the variability of in situ profile shapes under a variety of meteorological and pollution conditions, results are presented of an agglomerative hierarchical cluster analysis of the in situ O3 and NO2 profiles for each of the four campaigns of the NASA DISCOVER-AQ mission. Understanding the observed profile variability for these trace gases is useful for understanding the accuracy of the assumed profile shapes used in satellite retrieval algorithms as well as for understanding the correlation between satellite column observations and surface concentrations. The four campaigns of the DISCOVER-AQ mission took place in Maryland during July 2011, the San Joaquin Valley of California during January–February 2013, the Houston, Texas, metropolitan region during September 2013, and the Denver-Front Range region of Colorado during July–August 2014. Several distinct profile clusters emerged for the California, Texas, and Colorado campaigns for O3, indicating significant variability of O3 profile shapes, while the Maryland campaign presented only one distinct O3 cluster. In contrast, very few distinct profile clusters emerged for NO2 during any campaign for this particular clustering technique, indicating the NO2 profile behavior was relatively uniform throughout each campaign. However, changes in NO2 profile shape were evident as the boundary layer evolved through the day, but they were apparently not significant enough to yield more clusters. The degree of vertical mixing (as indicated by temperature lapse rate) associated with each cluster exerted an important influence on the shapes of the median cluster profiles for O3, as well as impacted the correlations between the associated column and surface data for each cluster for O3. The correlation analyses suggest satellites may have the best chance to relate to surface O3 under the conditions encountered during the Maryland campaign Clusters 1 and 2, which include deep, convective boundary layers and few interruptions to this connection from complex meteorology, chemical environments, or orography. The regional CMAQ model captured the shape factors for O3, and moderately well captured the NO2 shape factors, for the conditions associated with the Maryland campaign, suggesting that a regional air quality model may adequately specify a priori profile shapes for remote sensing retrievals. CMAQ shape factor profiles were not as well represented for the other regions.

The locus coeruleus (LC) is a critical node in the stress response, and its activation has been shown to promote hypervigilance and anxiety-like behavior. This noradrenergic nucleus has historically been considered homogeneous with highly divergent neurons that operate en masse to collectively affect central nervous system function and behavioral state. However, in recent years, LC has been identified as a heterogeneous structure whose neurons innervate discrete terminal fields and contribute to distinct aspects of behavior. We have previously shown that in late adolescent male rats, an acute traumatic stressor, simultaneous physical restraint and exposure to predator odor, preferentially induces c-Fos expression in a subset of dorsal LC neurons and persistently increases anxiety-like behavior. To investigate how these neurons respond to and contribute to the behavioral response to stress, we used a combination of retrograde tracing, whole-cell patch clamp electrophysiology, and chemogenetics. Here we show that LC neurons innervating the central nucleus of the amygdala (CeA) and medial prefrontal cortex (mPFC) undergo distinct electrophysiological changes in response to stressor exposure and have opposing roles in mediating anxiety-like behavior. While neurons innervating CeA become more excitable in response to stress and promote anxiety-like behavior, those innervating mPFC become less excitable and appear to promote exploration. These findings show that LC neurons innervating distinct terminal fields have unique physiological responses to particular stimuli. Furthermore, these observations advance the understanding of the LC as a complex and heterogeneous structure whose neurons maintain unique roles in various forms of behavior., Highlights • Locus coeruleus-central amygdala projections are hyperactive one week after stress. • Locus coeruleus-prefrontal cortex projections are hypoactive one week after stress. • Chemogenetic manipulation of each pathway distinctly affects anxiety-like behavior.

We quantify both the spatial and temporal variability of column integrated O3, NO2, CO, SO2, and HCHO over the Baltimore/Washington, DC area using output from the Weather Research and Forecasting model with on-line chemistry (WRF/Chem) for the entire month of July 2011, coinciding with the first deployment of the NASA Earth Venture program mission Deriving Information on Surface conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER-AQ). Using structure function analyses, we find that the model reproduces the spatial variability observed during the campaign reasonably well, especially for O3. The Tropospheric Emissions: Monitoring of Pollution (TEMPO) instrument will be the first NASA mission to make atmospheric composition observations from geostationary orbit and partially fulfills the goals of the Geostationary Coastal and Air Pollution Events (GEO-CAPE) mission. We relate the simulated variability to the precision requirements defined by the science traceability matrices of these space-borne missions. Results for O3 from 0 to 2 km altitude indicate that the TEMPO instrument would be able to observe O3 air quality events over the Mid-Atlantic area, even on days when the violations of the air quality standard are not widespread. The results further indicated that horizontal gradients in CO from 0 to 2 km would be observable over moderate distances (≥20 km). The spatial and temporal results for tropospheric column NO2 indicate that TEMPO would be able to observe not only the large urban plumes at times of peak production, but also the weaker gradients between rush hours. This suggests that the proposed spatial and temporal resolutions for these satellites as well as their prospective precision requirements are sufficient to answer the science questions they are tasked to address.

High spatial- and temporal-resolution ozone lidar profiles, in conjunction with ozonesonde and satellite observations, are well suited to characterize short-term ozone variations due to different physical and chemical processes, such as the impact of lightning-generated NOx (LNOx) on tropospheric ozone. This work presents the hourly variation of tropospheric-ozone profiles measured by an ozone lidar at the University of Alabama in Huntsville, on July 14, 18, and 27, 2011. These ozone lidar data are compared with two WRF/Chem simulations, one with lightning NO (LNO) emissions and the other without. On July 14, 2011, the ozone lidar observed an ozone laminar structure with elevated ozone concentrations of 65∼80 ppbv below 2 km, low ozone (50∼65) ppbv between 2 and 5 km, and high ozone up to 165 ppbv between 5 and 12 km AGL. WRF/Chem simulations, in conjunction with backward trajectory analysis, suggest that lightning events occurring within upwind regions resulted in an ozone enhancement of 28 ppbv at 7.5 km AGL over Huntsville. On July 27, LNO emissions were transported to Huntsville from upwind and account for 75% of NOx and an 8.3 ppbv of ozone enhancement at ∼10 km; the model overestimates ozone between 2.5 and 5 km AGL.

Emissions of nitrogen oxides (NOx) and, subsequently, atmospheric levels of nitrogen dioxide (NO2) have decreased over the U.S. due to a combination of environmental policies and technological change. Consequently, NO2 levels have decreased by 30–40% in the last decade. We quantify NO2 trends (2005–2013) over the U.S. using surface measurements from the U.S. Environmental Protection Agency (EPA) Air Quality System (AQS) and an improved tropospheric NO2 vertical column density (VCD) data product from the Ozone Monitoring Instrument (OMI) on the Aura satellite. We demonstrate that the current OMI NO2 algorithm is of sufficient maturity to allow a favorable correspondence of trends and variations in OMI and AQS data. Our trend model accounts for the non-linear dependence of NO2 concentration on emissions associated with the seasonal variation of the chemical lifetime, including the change in the amplitude of the seasonal cycle associated with the significant change in NOx emissions that occurred over the last decade. The direct relationship between observations and emissions becomes more robust when one accounts for these non-linear dependencies. We improve the OMI NO2 standard retrieval algorithm and, subsequently, the data product by using monthly vertical concentration profiles, a required algorithm input, from a high-resolution chemistry and transport model (CTM) simulation with varying emissions (2005–2013). The impact of neglecting the time-dependence of the profiles leads to errors in trend estimation, particularly in regions where emissions have changed substantially. For example, trends calculated from retrievals based on time-dependent profiles offer 18% more instances of significant trends and up to 15% larger total NO2 reduction versus the results based on profiles for 2005. Using a CTM, we explore the theoretical relation of the trends estimated from NO2 VCDs to those estimated from ground-level concentrations. The model-simulated trends in VCDs strongly correlate with those estimated from surface concentrations (r = 0.83, N = 355). We then explore the observed correspondence of trends estimated from OMI and AQS data. We find a significant, but slightly weaker, correspondence (i.e., r = 0.68, N = 208) than predicted by the model and discuss some of the important factors affecting the relationship, including known problems (e.g., NOz interferents) associated with the AQS data. This significant correspondence gives confidence in trend and surface concentration estimates from OMI VCDs for locations, such as the majority of the U.S. and globe, that are not covered by surface monitoring networks. Using our improved trend model and our enhanced OMI data product, we find that both OMI and AQS data show substantial downward trends from 2005 to 2013, with an average reduction of 38% for each over the U.S. The annual reduction rates inferred from OMI and AQS measurements are larger (−4.8 ± 1.9%/yr, −3.7 ± 1.5%/yr) from 2005 to 2008 than 2010 to 2013 (−1.2 ± 1.2%/yr, −2.1 ± 1.4%/yr). We quantify NO2 trends for major U.S. cities and power plants; the latter suggest larger negative trend (−4.0 ± 1.5%/yr) between 2005 and 2008 and smaller or insignificant changes (−0.5 ± 1.2%/yr) during 2010–2013.

National emission inventories (NEIs) take years to assemble, but they can become outdated quickly, especially for time-sensitive applications such as air quality forecasting. This study compares multi-year NO x trends derived from satellite and ground observations and uses these data to evaluate the updates of NO x emission data by the US National Air Quality Forecast Capability (NAQFC) for next-day ozone prediction during the 2008 Global Economic Recession. Over the eight large US cities examined here, both the Ozone Monitoring Instrument (OMI) and the Air Quality System (AQS) detect substantial downward trends from 2005 to 2012, with a seven-year total of −35% according to OMI and −38% according to AQS. The NO x emission projection adopted by NAQFC tends to be in the right direction, but at a slower reduction rate (−25% from 2005 to 2012), due likely to the unaccounted effects of the 2008 economic recession. Both OMI and AQS datasets display distinct emission reduction rates before, during, and after the 2008 global recession in some cities, but the detailed changing rates are not consistent across the OMI and AQS data. Our findings demonstrate the feasibility of using space and ground observations to evaluate major updates of emission inventories objectively. The combination of satellite, ground observations, and in-situ measurements (such as emission monitoring in power plants) is likely to provide more reliable estimates of NO x emission and its trend, which is an issue of increasing importance as many urban areas in the US are transitioning to NO x -sensitive chemical regimes by continuous emission reductions.

Satellite data of atmospheric pollutants are becoming more widely used in the decision-making and environmental management activities of public, private sector and non-profit organizations. They are employed for estimating emissions, tracking pollutant plumes, supporting air quality forecasting activities, providing evidence for “exceptional event” declarations, monitoring regional long-term trends, and evaluating air quality model output. However, many air quality managers are not taking full advantage of the data for these applications nor has the full potential of satellite data for air quality applications been realized. A key barrier is the inherent difficulties associated with accessing, processing, and properly interpreting observational data. A degree of technical skill is required on the part of the data end-user, which is often problematic for air quality agencies with limited resources. Therefore, we 1) review the primary uses of satellite data for air quality applications, 2) provide some background information on satellite capabilities for measuring pollutants, 3) discuss the many resources available to the end-user for accessing, processing, and visualizing the data, and 4) provide answers to common questions in plain language.

To investigate the ability of column (or partial column) information to represent surface air quality, results of linear regression analyses between surface mixing ratio data and column abundances for O3 and NO2 are presented for the July 2011 Maryland deployment of the DISCOVER-AQ mission. Data collected by the P-3B aircraft, ground-based Pandora spectrometers, Aura/OMI satellite instrument, and simulations for July 2011 from the CMAQ air quality model during this deployment provide a large and varied data set, allowing this problem to be approached from multiple perspectives. O3 columns typically exhibited a statistically significant and high degree of correlation with surface data (R(sup 2) > 0.64) in the P- 3B data set, a moderate degree of correlation (0.16 < R(sup 2) < 0.64) in the CMAQ data set, and a low degree of correlation (R(sup 2) < 0.16) in the Pandora and OMI data sets. NO2 columns typically exhibited a low to moderate degree of correlation with surface data in each data set. The results of linear regression analyses for O3 exhibited smaller errors relative to the observations than NO2 regressions. These results suggest that O3 partial column observations from future satellite instruments with sufficient sensitivity to the lower troposphere can be meaningful for surface air quality analysis.

During a classic heat wave with record high temperatures and poor air quality from July 18 to 23, 2011, an elevated reservoir of air pollutants was observed over and downwind of Baltimore, MD, with relatively clean conditions near the surface. Aircraft and ozonesonde measurements detected approximately 120 parts per billion by volume ozone at 800 meters altitude, but approximately 80 parts per billion by volume ozone near the surface. High concentrations of other pollutants were also observed around the ozone peak: approximately 300 parts per billion by volume CO at 1200 meters, approximately 2 parts per billion by volume NO2 at 800 meters, approximately 5 parts per billion by volume SO2 at 600 meters, and strong aerosol optical scattering (2 x 10 (sup 4) per meter) at 600 meters. These results suggest that the elevated reservoir is a mixture of automobile exhaust (high concentrations of O3, CO, and NO2) and power plant emissions (high SO2 and aerosols). Back trajectory calculations show a local stagnation event before the formation of this elevated reservoir. Forward trajectories suggest an influence on downwind air quality, supported by surface ozone observations on the next day over the downwind PA, NJ and NY area. Meteorological observations from aircraft and ozonesondes show a dramatic veering of wind direction from south to north within the lowest 5000 meters, implying that the development of the elevated reservoir was caused in part by the Chesapeake Bay breeze. Based on in situ observations, Community Air Quality Multi-scale Model (CMAQ) forecast simulations with 12 kilometers resolution overestimated surface ozone concentrations and failed to predict this elevated reservoir; however, CMAQ research simulations with 4 kilometers and 1.33 kilometers resolution more successfully reproduced this event. These results show that high resolution is essential for resolving coastal effects and predicting air quality for cities near major bodies of water such as Baltimore on the Chesapeake Bay and downwind areas in the Northeast.

Air quality models, such as the Community Multiscale Air Quality (CMAQ) model, indicate decidedly higher ozone near the surface of large interior water bodies, such as the Great Lakes and Chesapeake Bay. In order to test the validity of the model output, we performed surface measurements of ozone (O3) and total reactive nitrogen (NOy) on the 26-m Delaware II NOAA Small Research Vessel experimental (SRVx), deployed in the Chesapeake Bay for 10 daytime cruises in July 2011 as part of NASA’s GEO-CAPE CBODAQ oceanographic field campaign in conjunction with NASA’s DISCOVER-AQ air quality field campaign. During this 10-day period, the EPA O3 regulatory standard of 75 ppbv averaged over an 8-h period was exceeded four times over water while ground stations in the area only exceeded the standard at most twice. This suggests that on days when the Baltimore/Washington region is in compliance with the EPA standard, air quality over the Chesapeake Bay might exceed the EPA standard. Ozone observations over the bay during the afternoon were consistently 10e20% higher than the closest upwind ground sites during the 10-day campaign; this pattern persisted during good and poor air quality days. A lower boundary layer, reduced cloud cover, slower dry deposition rates, and other lesser mechanisms, contribute to the local maximum of ozone over the Chesapeake Bay. Observations from this campaign were compared to a CMAQ simulation at 1.33 km resolution. The model is able to predict the regional maximum of ozone over the Chesapeake Bay accurately, but NOy concentrations are significantly overestimated. Explanations for the overestimation of NOy in the model simulations are also explored.

We show that Aura Ozone Monitoring Instrument (OMI) nitrogen dioxide (NO2) tropospheric column data may be used to assess changes of the emissions of nitrogen oxides (NOx) from power plants in the United States, though careful interpretation of the data is necessary. There is a clear response for OMI NO2 data to NOx emission reductions from power plants associated with the implementation of mandated emission control devices (ECDs) over the OMI record (2005–2011). This response is scalar for all intents and purposes, whether the reduction is rapid or incremental over several years. However, it is variable among the power plants, even for those with the greatest absolute decrease in emissions. We document the primary causes of this variability, presenting case examples for specific power plants.

One of the important science requirements of the Geostationary Coastal and Air Pollution Events (GEO-CAPE) mission is to be able to measure ozone with two degrees of freedom in the troposphere and sensitivity in the lowest 2 km (lowermost troposphere, LMT), in order to characterize air quality and boundary layer transport of pollution. Currently available remote sensing techniques utilize backscattered solar ultraviolet (UV) radiances or thermal infrared (TIR) emissions to perform ozone retrievals. However, in the TIR, measurement sensitivity to the LMT requires high thermal contrast between the Earth’s surface and the near-surface (tens to hundreds of meters above surface) atmosphere, while in the UV, the measurement sensitivity to the LMT is low because of Rayleigh scattering. In this paper, we explore the feasibility of using multi-spectral intensity measurements in the UV, visible (VIS), mid infrared (MIR) and TIR, and polarization measurements in the UV/VIS, to improve tropospheric and lowermost tropospheric ozone retrievals. Simulations for 16 cloud and aerosol free atmospheric profiles spanning a range of ozone mixing ratios indicate that adding VIS measurements to UV measurements significantly enhances the sensitivity to lowermost tropospheric ozone, but only makes a slight improvement to the total degrees of freedom for signal (DFS). On the other hand, the combination of UV and TIR significantly improves the total DFS as well as the lowermost tropospheric DFS. The analysis presented here is a necessary and important first step for defining spectral regions that can meet the GEO-CAPE measurement requirements, and subsequently, the requirements for instrumentation. In this work, the principle of multi-spectral retrievals has been extended from previously published literature and we show that the UV + VIS, UV + TIR and UV + VIS + TIR combinations have the potential to meet the GEO-CAPE measurement requirements for tropospheric ozone. Our analysis includes errors from water and surface properties; further analysis is needed to include temperature, additional gas interferents, clouds, aerosols and more realistic surface properties. These simulations must be run on a much larger dataset, followed by OSSEs (Observing System Simulation Experiments), where simulated retrievals are assimilated into chemical-transport models, to quantitatively assess the impact of the proposed measurements for constraining the spatiotemporal distribution of ozone in the LMT for basic science studies and applications such as air quality forecasts.

Two fine-scale meteorological processes, fair-weather cumulus cloud development and a bay breeze, are examined along with their impacts on air chemistry. The impact of model resolution on fair-weather cumulus cloud development, transport of pollutants through clouds, sulfur dioxide to sulfate conversion in clouds, and the development of the Chesapeake Bay breeze are examined via 13.5, 4.5, 1.5, and 0.5 km resolution simulations covering the Washington – Baltimore area. Results show that as the resolution increases, more pollutants are transported aloft through fair-weather cumulus clouds causing an increase in the rate of oxidation of sulfur dioxide to sulfate aerosols. The high resolution model runs more nearly match observations of a local pollutant maximum near the top of the boundary layer and produce an increase in boundary layer venting with subsequent pollutant export. The sensitivity of sulfur dioxide to sulfate conversion rates to cloud processing is examined by comparing sulfur dioxide and sulfate concentrations from simulations that use two different methods to diagnose clouds. For this particular event, a diagnostic method produces the most clouds and the most realistic cloud cover, has the highest oxidation rates, and generates sulfur dioxide and sulfate concentrations that agree best with observations. The differences between the simulations show the importance of accurately simulating clouds in sulfate simulations. The fidelity of the model’s representation of the bay breeze is examined as a function of resolution. As the model resolution increases, a larger temperature gradient develops along the shoreline of the Chesapeake Bay causing the bay breeze to form sooner, push farther inland, and loft more pollutants upward. This stronger bay breeze results in low-level convergence, a buildup of near surface ozone over land and a decrease in the land-to-sea flux of ozone and ozone precursors as seen in measurements. The resulting 8 h maximum ozone concentration over the Bay is 10 ppbv lower in the 0.5 km simulation than in the 13.5 km simulation.

We investigated variations in the relative sensitivity of surface ozone formation in summer to precursor species concentrations of volatile organic compounds (VOCs) and nitrogen oxides (NOx) as inferred from the ratio of the tropospheric columns of formaldehyde to nitrogen dioxide (the "Ratio") from the Aura Ozone Monitoring Instrument (OMI). Our modeling study suggests that ozone formation decreases with reductions in VOCs at Ratios less than 1 and NOx at Ratios greater than 2; both NOx and VOC reductions may decrease ozone formation for Ratios between 1 and 2. Using this criteria. the OMI data indicate that ozone formation became: 1. more sensitive to NOx over most of the United States from 2005 to 2007 because of the substantial decrease in NOx emissions, primarily from stationary sources, and the concomitant decrease in the tropospheric column of NO2. and 2. more sensitive to NOx with increasing temperature, in part because emissions of highly reactive, biogenic isoprene increase with temperature, thus increasing the total VOC reactivity. In cities with relatively low isoprene emissions (e.g .. Chicago). the data clearly indicate that ozone formation became more sensitive to NOx from 2005 to 2007. In cities with relatively high isoprene emissions (e.g ., Atlanta), we found that the increase in the Ratio due to decreasing NOx emissions was not obvious as this signal was convolved with variations in the Ratio associated with the temperature dependence of isoprene emissions and, consequently, the formaldehyde concentration.

Summary Objective To examine whether urine concentrations of type II collagen neoepitope (uTIINE) distinguish subjects with progressive radiographic and/or symptomatic knee osteoarthritis (OA) from those with stable disease. Methods Subjects were 120 obese middle-aged women with unilateral knee OA who participated in a 30-month randomized-controlled trial of structure modification with doxycycline, in which a standardized semiflexed anteroposterior view of the knee was obtained at baseline, 16 months and 30 months. Subjects were selected from a larger sample to permit a priori comparisons between 60 OA progressors and 60 nonprogressors, as defined by joint space narrowing (JSN) in the medial tibiofemoral compartment. Each group contained 30 subjects who exhibited clinically significant increases in knee pain over 30 months and 30 who did not. Urine samples were obtained every 6 months for determination of the creatinine (Cr)-adjusted uTIINE concentration. Results Baseline uTIINE levels were unrelated to JSN in the placebo group. However, among subjects in the active treatment group, a 1-standard deviation increment in baseline uTIINE (68ng/mM Cr) was associated with a marginally significant, two-fold increase in the odds of progression of JSN (odds ratio 2.04, 95% confidence interval 0.98–4.28). The within-subject mean of uTIINE values at baseline, 6 months and 12 months was associated with concurrent JSN measured at 16 months (0.10mm of JSN per 69ng/mM Cr, P =0.008). Similar results were seen in the interval between months 16 and 30 and in analyses using the maximum of intercurrent uTIINE levels. Conclusion Baseline uTIINE was not a consistent predictor of JSN in subjects with knee OA. However, serial measurements of uTIINE reflect concurrent JSN.

SummaryObjectiveRecent studies using various standardized radiographic acquisition techniques have demonstrated the necessity of reproducible radioanatomic alignment of the knee to assure precise measurements of medial tibiofemoral joint space width (JSW). The objective of the present study was to characterize the longitudinal performance of several acquisition techniques with respect to long-term reproducibility of positioning of the knee, and the impact of changes in positioning on the rate and variability of joint space narrowing (JSN).MethodsEighty subjects were randomly selected from each of three cohorts followed in recent studies of the radiographic progression of knee osteoarthritis (OA): the Health ABC study (paired fixed-flexion [FF] radiographs taken at a 36-month interval); the Glucosamine Arthritis Intervention Trial (GAIT) (paired metatarsophalangeal [MTP] radiographs obtained at a 12-month interval), and a randomized clinical trial of doxycycline (fluoroscopically assisted semiflexed anteroposterior (AP) radiographs taken at a 16-month interval).Manual measurements were obtained from each radiograph to represent markers of radioanatomic positioning of the knee (alignment of the medial tibial plateau and X-ray beam, knee rotation, femorotibial angle) and to evaluate minimum JSW (mJSW) in the medial tibiofemoral compartment. The effects on the mean annualized rate of JSN and on the variability of that rate of highly reproduced vs variable positioning of the knee in serial radiographs were evaluated.ResultsParallel or near-parallel alignment was achieved significantly more frequently with the fluoroscopically guided positioning used in the semiflexed AP protocol than with either the non-fluoroscopic FF or MTP protocol (68% vs 14% for both FF and MTP protocols when measured at the midpoint of the medial compartment; 75% vs 26% and 34% for the FF and MTP protocols, respectively, when measured at the site of mJSW; P

We review the pattern of activity in the parasympathetic and sympathetic nerves innervating the heart. Unlike the conventional textbook picture of reciprocal control of cardiac vagal and sympathetic nervous activity, as seen during a baroreceptor reflex, many other reflexes involve simultaneous co-activation of both autonomic limbs. Indeed, even at 'rest', the heart receives tonic drives from both sympathetic and parasympathetic cardiac nerves. Autonomic co-activation occurs during peripheral chemoreceptor, diving, oculocardiac, somatic nociceptor reflex responses as well as being evoked from structures within the brain. It is suggested that simultaneous co-activation may lead to a more efficient cardiac function giving greater cardiac output than activation of the sympathetic limb alone; this permits both a longer time for ventricular filling and a stronger contraction of the myocardium. This may be important when pumping blood into a constricted vascular tree such as is the case during the diving response. We discuss that in some instances, high drive to the heart from both autonomic limbs may also be arrhythmogenic.

Many current global chemistry-transport models limit the annual global source strength of reactive nitrogen from lightning activity to ∼5 Tg N yr −1 . However, there is strong evidence from aircraft and cloud-resolving model studies and theory that production of NO by an intracloud flash is not an order of magnitude smaller than from a cloud-to-ground flash, an assumption commonly used in the global models. We suggest that modification of the global models to accept comparable production of NO by both types of discharge and the necessarily larger input of NO to higher altitudes will require a reduction in their global annual source strength from lightning activity in order to match existing observations.

Summary Objective To evaluate the prevalence of synovitis in painful medial tibiofemoral knee osteoarthritis (OA) and to evaluate correlation between synovitis and the structural severity and progression of tibiofemoral cartilage damage. Design Study : multicenter, longitudinal, 1-year duration. Patients : primary painful knee OA (ACR criteria) of the medial tibiofemoral compartment, with pain of the signal knee on at least 30 days in the past 2 months, medial joint space width ≥2mm, at least 10% of one cartilage surface of the medial compartment affected by superficial fibrillation or worse at baseline arthroscopy. Arthroscopic parameters : knee arthroscopy under local anesthesia was performed and videorecorded at entry and after 1 year. Medial chondropathy was scored by using Societe Francaise d'Arthroscopie (SFA) score (0–100) and reader's overall assessment (VAS score, 100mm). Progression of medial chondropathy was defined by a change in SFA and VAS scores over 4.5 and 8.0mm after 1 year, respectively. Medial perimeniscal synovium was scored as normal (few translucent and slender villi, fine vascular network), reactive (proliferation of opaque villi), or inflammatory (hypervascularization and/or proliferation of hypertrophic and hyperemic villi). Medial chondropathy and synovitis were scored by a single reader blind to chronology of paired videotapes. Results Four hundred and twenty-two patients were enrolled (mean age: 61 years, females: 59%, body mass index: 31, mean disease duration: 4 years) and completed the 1-year study. Synovial abnormalities were present in 50% of the patients with reactive and inflammatory aspects in 29% and 21% of the patients, respectively. Patients with a reactive or inflammatory medial synovium had a more severe medial chondropathy. The worsening in medial chondropathy after 1 year was statistically more severe in the group of patients with an inflammatory perimeniscal synovial membrane at baseline compared to patients with normal and reactive aspects, with no difference between these two latter groups. The odds ratio for progression in VAS score after 1 year was 3.11 (95% CI [1.07, 5.69]) for patients with inflammatory synovium at baseline compared to patients with normal synovium. Conclusions This study suggests that abnormalities of the medial perimeniscal synovium are a common feature of painful medial knee OA, associated with more severe medial chondropathy. It also suggests that an inflammatory aspect of the medial perimeniscal synovium could be considered as a predictive factor of subsequent increased degradation of medial chondropathy.

Current and projected (up to 2050 A.D.) concentrations of boundary layer trace gases, including NO x , CO, CH 4 , and several nonmethane hydrocarbons were redistributed throughout the troposphere in a simulation of a central U.S. squall line using the Goddard Cumulus Ensemble (GCE) convective cloud model. Vertical profiles of the redistributed trace gases were used in a one-dimensional photochemical model to determine the vertical profile of the potential production of 0 3 . Several different emission scenarios were considered. In the case where NO x emissions were doubled along with an increase in CO, CH 4 , and NMHC's, the middle troposphere showed an enhancement of 41% for O 3 production relative to the 1985 case. For the reduction scenario, where NO x emissions were decreased by a factor of two, the O 3 produced in the middle troposphere was reduced by 50%. Given the role of convection in the regional O 3 budget of the central U.S. during the summertime, our results suggest that substantial changes in emissions could bring about changes in mid-tropospheric O 3 large enough to be observed by satellite remote sensing.

Whole-cell patch-clamp recordings (WCR) were made from sympathetic preganglionic neurons (SPN) in neonate rat spinal cord slices. SPN were identified histologically by filling them with the fluorescent dye Lucifer Yellow contained within the patch pipette solution. Current clamp recordings were obtained from SPN with a potassium based pipette solution. The cells exhibited many of the characteristic properties of SPN seen previously with intracellular recordings in both the rat and the cat. However, we found an order of magnitude increase in both cell input resistance (950 M omega) and time constant (118 ms) over those seen with conventional recordings. We believe these values approximate better the situation in intact cells, and will have a vital bearing upon how SPN integrate inputs. We conclude that WCR in spinal cord slices provides a powerful tool for investigating the cellular properties of SPN.