Anthropogenic control over wintertime oxidation of atmospheric pollutants.

During winter in the mid-latitudes, photochemical oxidation is significantly slower than in summer and the main radical oxidants driving formation of secondary pollutants, such as fine particulate matter and ozone, remain uncertain, owing to a lack of observations in this season. Using airborne observations, we quantify the contribution of various oxidants on a regional basis during winter, enabling improved chemical descriptions of wintertime air pollution transformations. We show that 25-60% of NOx is converted to N2O5 via multiphase reactions between gas-phase nitrogen oxide reservoirs and aerosol particles, with ~93% reacting in the marine boundary layer to form >2.5 ppbv ClNO2. This results in >70% of the oxidizing capacity of polluted air during winter being controlled, not by typical photochemical reactions, but from these multiphase reactions and emissions of volatile organic compounds, such as HCHO, highlighting the control local anthropogenic emissions have on the oxidizing capacity of the polluted wintertime atmosphere.

Ozone production chemistry in the presence of urban plumes.

Ozone pollution affects human health, especially in urban areas on hot sunny days. Its basic photochemistry has been known for decades and yet it is still not possible to correctly predict the high ozone levels that are the greatest threat. The CalNex_SJV study in Bakersfield CA in May/June 2010 provided an opportunity to examine ozone photochemistry in an urban area surrounded by agriculture. The measurement suite included hydroxyl (OH), hydroperoxyl (HO2), and OH reactivity, which are compared with the output of a photochemical box model. While the agreement is generally within combined uncertainties, measured HO2 far exceeds modeled HO2 in NOx-rich plumes. OH production and loss do not balance as they should in the morning, and the ozone production calculated with measured HO2 is a decade greater than that calculated with modeled HO2 when NO levels are high. Calculated ozone production using measured HO2 is twice that using modeled HO2, but this difference in calculated ozone production has minimal impact on the assessment of NOx-sensitivity or VOC-sensitivity for midday ozone production. Evidence from this study indicates that this important discrepancy is not due to the HO2 measurement or to the sampling of transported plumes but instead to either emissions of unknown organic species that accompany the NO emissions or unknown photochemistry involving nitrogen oxides and hydrogen oxides, possibly the hypothesized reaction OH + NO + O2 → HO2 + NO2.

Molecular Composition and Volatility of Organic Aerosol in the Southeastern U.S.: Implications for IEPOX Derived SOA.

We present measurements as part of the Southern Oxidant and Aerosol Study (SOAS) during which atmospheric aerosol particles were comprehensively characterized. We present results utilizing a Filter Inlet for Gases and AEROsol coupled to a chemical ionization mass spectrometer (CIMS). We focus on the volatility and composition of isoprene derived organic aerosol tracers and of the bulk organic aerosol. By utilizing the online volatility and molecular composition information provided by the FIGAERO-CIMS, we show that the vast majority of commonly reported molecular tracers of isoprene epoxydiol (IEPOX) derived secondary organic aerosol (SOA) is derived from thermal decomposition of accretion products or other low volatility organics having effective saturation vapor concentrations <10(-3) µg m(-3). In addition, while accounting for up to 30% of total submicrometer organic aerosol mass, the IEPOX-derived SOA has a higher volatility than the remaining bulk. That IEPOX-SOA, and more generally bulk organic aerosol in the Southeastern U.S. is comprised of effectively nonvolatile material has important implications for modeling SOA derived from isoprene, and for mechanistic interpretations of molecular tracer measurements. Our results show that partitioning theory performs well for 2-methyltetrols, once accretion product decomposition is taken into account. No significant partitioning delays due to aerosol phase or viscosity are observed, and no partitioning to particle-phase water or other unexplained mechanisms are needed to explain our results.

Olfaction in the Anthropocene: NO3 negatively affects floral scent and nocturnal pollination.

There is growing concern about sensory pollutants affecting ecological communities. Anthropogenically enhanced oxidants [ozone (O3) and nitrate radicals (NO3)] rapidly degrade floral scents, potentially reducing pollinator attraction to flowers. However, the physiological and behavioral impacts on pollinators and plant fitness are unknown. Using a nocturnal flower-moth system, we found that atmospherically relevant concentrations of NO3 eliminate flower visitation by moths, and the reaction of NO3 with a subset of monoterpenes is what reduces the scent's attractiveness. Global atmospheric models of floral scent oxidation reveal that pollinators in certain urban areas may have a reduced ability to perceive and navigate to flowers. These results illustrate the impact of anthropogenic pollutants on an animal's olfactory ability and indicate that such pollutants may be critical regulators of global pollination.

PspK of Streptococcus pneumoniae increases adherence to epithelial cells and enhances nasopharyngeal colonization.

Streptococcus pneumoniae (the pneumococcus) colonizes the human nasopharynx and can cause invasive disease aided by the pneumococcal capsule. Group II nontypeable S. pneumoniae (NTSp) lacks a polysaccharide capsule, and a subgroup of NTSp carriage isolates has been found to have a novel gene, pneumococcal surface protein K (pspK), which replaces the capsule locus. A recent rise in the number of NTSp isolates colonizing the human nasopharynx has been observed, but the colonization factors of NTSp have not been well studied. PspK has been shown to play a role in mouse colonization. We therefore examined PspK-mediated immune evasion along with adherence to host cells and colonization. PspK bound human secretory immunoglobulin A (sIgA) but not the complement regulator factor H and did not decrease C3b deposition on the pneumococcal surface. PspK increased binding of pneumococci to epithelial cells and enhanced pneumococcal colonization independently of the genetic background. Understanding how NTSp colonizes and survives within the nasopharynx is important due to the increase in NTSp carriage. Our data suggest that PspK may aid in the persistence of NTSp within the nasopharynx but is not involved in invasion.

Quantifying trace gas uptake to tropospheric aerosol: recent advances and remaining challenges.

The interactions of trace gases with tropospheric aerosol can have significant effects on both gas phase and aerosol composition. In turn, this may affect the atmospheric oxidizing capacity, aerosol hygroscopicity and optical properties, and the lifetimes of trace aerosol species. Through the detailed description of specific reaction systems, this review article illustrates how detailed experimental studies of gas-particle interactions lead to both a comprehensive understanding of the underlying physical chemistry as well as accurate parameterizations for atmospheric modeling. The reaction systems studied illustrate the complexity in the field: (i) N(2)O(5) uptake, presented as a benchmark multiphase system, can lead to both NO(x) loss and halogen activation, (ii) loss of HO(2) on aqueous particles is surprisingly poorly studied given its potential importance for HO(x) loss, (iii) uptake of HNO(3) by marine aerosol and heterogeneous oxidation of organic-bearing particles are examples of how gas-particle interactions can lead to substantial alteration of aerosol composition, and (iv) the uptake of glyoxal to ammonium sulfate aerosol leads to highly complex particle-phase chemistry. In addition, for the first time, this article presents the challenges that must be addressed in the design and interpretation of atmospheric gas-to-particle uptake experiments.

Formaldehyde production from isoprene oxidation across NOx regimes.

The chemical link between isoprene and formaldehyde (HCHO) is a strong, non-linear function of NOx (= NO + NO2). This relationship is a linchpin for top-down isoprene emission inventory verification from orbital HCHO column observations. It is also a benchmark for overall photochemical mechanism performance with regard to VOC oxidation. Using a comprehensive suite of airborne in situ observations over the Southeast U.S., we quantify HCHO production across the urban-rural spectrum. Analysis of isoprene and its major first-generation oxidation products allows us to define both a "prompt" yield of HCHO (molecules of HCHO produced per molecule of freshly-emitted isoprene) and the background HCHO mixing ratio (from oxidation of longer-lived hydrocarbons). Over the range of observed NOx values (roughly 0.1 - 2 ppbv), the prompt yield increases by a factor of 3 (from 0.3 to 0.9 ppbv ppbv-1), while background HCHO increases by a factor of 2 (from 1.6 to 3.3 ppbv). We apply the same method to evaluate the performance of both a global chemical transport model (AM3) and a measurement-constrained 0-D steady state box model. Both models reproduce the NOx dependence of the prompt HCHO yield, illustrating that models with updated isoprene oxidation mechanisms can adequately capture the link between HCHO and recent isoprene emissions. On the other hand, both models under-estimate background HCHO mixing ratios, suggesting missing HCHO precursors, inadequate representation of later-generation isoprene degradation and/or under-estimated hydroxyl radical concentrations. Detailed process rates from the box model simulation demonstrate a 3-fold increase in HCHO production across the range of observed NOx values, driven by a 100% increase in OH and a 40% increase in branching of organic peroxy radical reactions to produce HCHO.

Instrumentation and Measurement Strategy for the NOAA SENEX Aircraft Campaign as Part of the Southeast Atmosphere Study 2013.

Natural emissions of ozone-and-aerosol-precursor gases such as isoprene and monoterpenes are high in the southeast of the US. In addition, anthropogenic emissions are significant in the Southeast US and summertime photochemistry is rapid. The NOAA-led SENEX (Southeast Nexus) aircraft campaign was one of the major components of the Southeast Atmosphere Study (SAS) and was focused on studying the interactions between biogenic and anthropogenic emissions to form secondary pollutants. During SENEX, the NOAA WP-3D aircraft conducted 20 research flights between 27 May and 10 July 2013 based out of Smyrna, TN. Here we describe the experimental approach, the science goals and early results of the NOAA SENEX campaign. The aircraft, its capabilities and standard measurements are described. The instrument payload is summarized including detection limits, accuracy, precision and time resolutions for all gas-and-aerosol phase instruments. The inter-comparisons of compounds measured with multiple instruments on the NOAA WP-3D are presented and were all within the stated uncertainties, except two of the three NO2 measurements. The SENEX flights included day- and nighttime flights in the Southeast as well as flights over areas with intense shale gas extraction (Marcellus, Fayetteville and Haynesville shale). We present one example flight on 16 June 2013, which was a daytime flight over the Atlanta region, where several crosswind transects of plumes from the city and nearby point sources, such as power plants, paper mills and landfills, were flown. The area around Atlanta has large biogenic isoprene emissions, which provided an excellent case for studying the interactions between biogenic and anthropogenic emissions. In this example flight, chemistry in and outside the Atlanta plumes was observed for several hours after emission. The analysis of this flight showcases the strategies implemented to answer some of the main SENEX science questions.

The interaction between monoamine oxidase inhibitors and narcotic analgesics in mice.

1. The administration of either iproniazid or tranylcypromine to mice potentiates the acute toxicity of pethidine, morphine, pentazocine and phenazocine.2. Blood levels of pentazocine in mice pretreated with tranylcypromine do not differ from the levels in animals not receiving the monoamine oxidase (MAO) inhibitor.3. There is no correlation between changes in brain and liver MAO activity and the increased pethidine toxicity.4. A comparison is made between the change in pethidine toxicity and the changes in the concentration of cerebral noradrenaline, dopamine and 5-hydroxytryptamine following the injection of tranylcypromine.5. It is concluded that the increased toxicity of potent analgesics in combination with MAO inhibitors is not due to a decelerated metabolism of the analgesic drug, but is related to an increased concentration of cerebral 5-hydroxytryptamine. A critical level of this monoamine, in the brain, may be necessary before the drug interaction will take place.

Rhinal cortex ablations fail to disrupt reinforcer devaluation effects in rhesus monkeys (Macaca mulatta).

Studies have shown that excitotoxic lesions of the amygdala attenuate reinforcer devaluation effects in monkeys and rats. Because the rhinal (i.e., entorhinal and perirhinal) cortex has prominent reciprocal connections with the amygdala and has been suggested to store knowledge about objects, it is possible that it too composes part of the critical circuitry subserving learning about objects and their associated reinforcement value. To test this possibility, rhesus monkeys with rhinal cortex removals as well as unoperated controls were tested using a reinforcer devaluation procedure. Monkeys with rhinal cortex removals and controls, unlike those with amygdala lesions, tended to avoid displacing objects overlying a devalued food. These results indicate that the rhinal cortex is not a critical part of the neural circuitry mediating the effects of reinforcer devaluation.

Comparative studies of a new commercial kit for the estimation of vitamin B12 in serum.

A commercial kit method (Technia Diagnostics) for the estimation of serum vitamin B12 claiming certain practical advantages was examined. Analytical and clinical performance were compared with a non-commercial radioisotope B12 method, previously compared to other commercial radioisotope B12 methods. The kit's analytical performance in our hands was satisfactory, although the within-batch precision and recovery of added cyanocobalamin were disappointing. Clinical performance was comparable with the non-commercial B12 method. Establishment of suitable reference ranges as a prerequisite to diagnostic use is apparent.

An evaluation of commercial radioisotope methods for the determination of folate and vitamin B12.

Five commercial kits for the determination of folate and six kits for the determination of vitamin B12 were investigated. Their performance has been compared with microbiological methods for the two vitamins and with a non-commercial radioisotopic method for B12. The results show the importance of the determination of the reference range for an individual laboratory for each method. The precision of the kits varied appreciably, as did their performance using specimens from patients with different haematological disorders. In particular, certain kits failed to detect all patients with pernicious anaemia. The relative accuracy of the kits was assessed. Various factors which should be taken into account in the final selection of a satisfactory kit are discussed.

The influence of associability changes in negative patterning and other discriminations.

Normal rats showed faster learning of a serial negative patterning (NP) discrimination (X+, A+, X-->A-) than of a comparable feature negative (FN) discrimination (A+, X-->A-). This advantage was absent in rats with lesions of the amygdala central nucleus. Earlier data indicated that this brain lesion interferes with surprise-induced increases in attention specified by the Pearce-Hall model (J. M. Pearce & G. Hall, 1980). In the NP task, but not the FN task, omission of the reinforcer after X on X-->A- trials was surprising. A variation of the NP task (NPX), in which X was reinforced on both X+ and X-->A- trials, was learned more rapidly than the NP task. Lesioned rats were unimpaired in learning the NPX task. Evaluation of the lesion effects and the results of posttraining transfer tests suggested that the NP advantage involved attentional processes, whereas the NPX advantage was based on the acquisition of inhibitory control by aspects of excitation conditioned to X.

Testing and analytical procedures for laboratory studies involving nonresponders during a limited observation period: an illustration using male sexual behavior in rats.

In many laboratory studies, a subpopulation of subjects fails to exhibit the response under investigation during the period of observation. For example, within any population of male rats, there is significant variation in the expression of sexual behavior in the presence of a receptive female. Some males may never display the full sequence of behaviors leading to ejaculation within the typical time frame of the testing session, with the resulting lack of behavioral response presenting problems in the analysis of the data. Conventional strategies range from screening such males from the study or dropping them from the analysis to constructing new variables based on estimates from existing parameters or increasing the length of the test session to capture sexual responses in a greater portion of males. Herein, we present an alternative strategy for analyzing data where outcomes are absent due to the limited observation period. Survival regression analysis enables inclusion of all subjects in the analysis whether or not they have shown the behavior of interest. Use of such a strategy not only has potential to reveal new results but also guards against bias from excluding nonresponders from the study or dropping more males from one experimental condition than another. Furthermore, this procedure can be helpful in generating the conditional probability (increase, decrease, or constant) of the response with the passage of time based on the hazard function and in estimating parameters for establishing an optimal behavioral test length for future studies.

Ventilatory effects of isoflurane: a comparison with halothane in a draw-over system.

Halothane and isoflurane were studied using a draw-over anaesthetic system in two groups each of 25 patients to compare the ventilatory effects of the two agents in field anaesthesia. Respiratory variables were measured and it was confirmed that isoflurane is a more potent respiratory depressant than halothane, but satisfactory anaesthesia for short procedures was possible.