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.

Bombardment-induced tunable superlattices in the growth of Au-Ni films.

Highly ordered superlattices are typically created through the sequential deposition of two different materials. Here, we report our experimental observation of spontaneous formation of superlattices in coevaporation of Au and Ni under energetic ion bombardment. The superlattice periodicities are on the order of a few nanometers and can be adjusted through the energy and flux of ion beams. Such a self-organization process is a consequence of the bombardment-induced segregation and uphill diffusion within the advancing nanoscale subsurface zone in the film growth. Our observations suggest that ion beams can be employed to make tunable natural superlattices in the deposition of phase-separated systems with strong bombardment-induced segregation.

Fossil-fueled power plants as a source of atmospheric carbon monoxide.

Elevated carbon monoxide (CO) mixing ratios in excess of those derived from emissions inventories have been observed in plumes from one gas- and coal-fired power plant and three of four lignite coal-fired electric utility power plants observed in east and central Texas. Observations of elevated CO on days characterized by differing wind directions show that CO emissions from the lignite plants were relatively constant over time and cannot be ascribed to separate sources adjacent to the power plants. These three plants were found to be emitting CO at rates 22 to 34 times those tabulated in State and Federal emissions inventories. Elevated CO emissions from the gas- and coal-fired plant were highly variable on time scales of hours to days, in one case changing by a factor of 8 within an hour. Three other fossil-fueled power plants, including one lignite-fired plant observed during this study, did not emit substantial amounts of CO, suggesting that a combination of plant operating conditions and the use of lignite coal may contribute to the enhanced emissions. Observed elevated CO emissions from the three lignite plants, if representative of average operating conditions, represent an additional 30% of the annual total CO emissions from point sources for the state of Texas.

Observations of ozone formation in power plant plumes and implications for ozone control strategies.

Data taken in aircraft transects of emissions plumes from rural U.S. coal-fired power plants were used to confirm and quantify the nonlinear dependence of tropospheric ozone formation on plume NO(x) (NO plus NO(2)) concentration, which is determined by plant NO(x) emission rate and atmospheric dispersion. The ambient availability of reactive volatile organic compounds, principally biogenic isoprene, was also found to modulate ozone production rate and yield in these rural plumes. Differences of a factor of 2 or greater in plume ozone formation rates and yields as a function of NO(x) and volatile organic compound concentrations were consistently observed. These large differences suggest that consideration of power plant NO(x) emission rates and geographic locations in current and future U.S. ozone control strategies could substantially enhance the efficacy of NO(x) reductions from these sources.

A prospective evaluation of elevated serum theophylline concentrations to determine if high concentrations are predictable.

PURPOSE: To evaluate prospectively whether serum theophylline concentrations of 25 mg/L and greater were predictable (and presumably preventable) by use of basic pharmacokinetic calculations. DESIGN: Prospective study. PATIENTS: Fifty-five patients with a serum theophylline concentration of at least 25.0 mg/L were evaluated initially and if subsequent elevated theophylline concentrations occurred. INTERVENTIONS: The predicted steady-state serum theophylline concentration was calculated from the dosage rate divided by the predicted clearance to determine how many elevated concentrations (greater than 20 mg/L) were predictable. Predicted clearances were 0.04 L/kg/hour for normal subjects less than 70 years of age and 0.02 L/kg/hour for patients with congestive heart failure, chronic obstructive pulmonary disease, or liver disease. Estimated clearances were determined and compared with predicted clearances. If patients did not have steady-state concentrations, additional calculations were made. MAIN RESULTS: From 6,368 consecutive theophylline determinations, 69 (1.08%) samples from 55 patients were 25 mg/L or higher. Predictably high concentrations occurred in 23 of 33 (69.7%) fully evaluable cases. These concentrations occurred because of a failure to consider decreased elimination clearance from congestive heart failure, chronic obstructive pulmonary disease, or hepatic disease. Five fatalities occurred, and in two cases, theophylline appeared to contribute to the patient's death. Three other patients experienced syncope. The predicted elimination clearance of theophylline of 0.02 L/kg/hour was too high in eight patients over 70 years old with cardiac or pulmonary disease. Nursing and pharmacy oversights were identified as three patients were given two theophylline products simultaneously. CONCLUSIONS: Most elevated theophylline concentrations are predictable (and preventable) by basic pharmacokinetic calculations. Patients experiencing elevated theophylline concentrations often had comorbid conditions and were greater than 60 years of age. The dosage rate of theophylline (mg/hour) can be estimated from predicted clearance (L/kg/hour) times desired steady-state serum concentration (mg/L).

Activation of renin-angiotensin system does not cause skeletal muscle cramps during hemodialysis.

Activation of the renin-angiotensin system usually occurs during hemodialysis and in hemodialyzed normal dogs parallels reductions in blood flow to a tissue group that is largely composed of skeletal muscle. To determine if excessive activation of this system might cause dialysis-associated skeletal muscle cramps in some patients, we conducted a double-blind, randomized and balanced trial in which 5 patients with frequent dialysis-associated cramps were each given either a 25 mg oral dose of captopril or placebo 1 h before 8 consecutive dialyses. Captopril increased the frequency of dialyses complicated by skeletal muscle cramps in 1 patient and did not affect cramp frequency in the other 4 patients. Predialysis plasma renin activity (PRA) averaged 3.9 ng/ml/h (+/- SD) and was the same as in unselected hemodialysis patients. Following captopril, PRA increased by an average of 2.2 +/- 0.7 times, similar to the 2.6-fold increase that was reported when this drug was used to prevent dialysis-associated hypertensive crises. However, hemodialysis by itself did not activate the renin-angiotensin system as consistently in patients with frequent dialysis-associated skeletal muscle cramps as in unselected hemodialysis patients and the ratio of post- to predialysis PRA averaged 1.0 +/- 0.6. We conclude that the renin-angiotensin system does not mediate, and that its activation during hemodialysis may actually help prevent, dialysis-associated skeletal muscle cramps.

Pharmacokinetics of N-acetylprocainamide in patients profiled with a stable isotope method.

N-Acetylprocainamide (NAPA) absorption and disposition were profiled in five patients with ventricular arrhythmias by the simultaneous intravenous administration of NAPA-13C and oral administration of a 500 mg NAPA hydrochloride tablet. NAPA distribution was modeled with a three compartment mammillary system. The central compartment volume of 14.1 +/- 2.6 L (mean +/- SD) was similar to expected intravascular space, corrected for NAPA partitioning between erythrocytes and plasma. Other compartment volumes, intercompartmental and nonrenal clearances, and the steady-state distribution volume of 1.45 +/- 0.09 L/kg were similar to normal subject values. The least-squares estimate of 1.67 for the NAPA renal clearance/creatinine clearance ratio was similar to the value of 1.68 previously reported for functionally anephric patients and showed the expected age-associated decrease. The oral NAPA dose was 78.0% +/- 11.7% absorbed and interindividual variation in NAPA absorption was correlated with fast intercompartmental clearance (r = 0.89, p = 0.045). Because fast intercompartmental clearance partly reflects splanchnic blood flow, hemodynamic changes may affect NAPA bioavailability, as has been found for procainamide.

Near infrared rugate filter fabrication by ion beam assisted deposition of Si((1-x))N(x) films.

The rugate filter employs a sinusoidal refractive index depth profile to produce high reflection in a narrow band of wavelengths. Fabrication relies on a continuously variable index of refraction in the wavelength regime of interest. The near IR refractive index of amorphous silicon-nitrogen films decreases continuously as the composition varies from pure silicon to stoichiometric silicon nitride (Si(3)N(4)). Ion implantation was found unsuitable as a fabrication method for rugate filters. Homogeneous and inhomogeneous films up to 5 microm in thickness have been produced by simultaneous deposition of electron beam evaporated silicon and of energetic nitrogen particles arising from an ion beam. The relative fluxes of beam and evaporant are found to determine the ratio of nitrogen to silicon in the films and therefore to determine the index. Single-band reflection filters of the rugate design of high peak optical density were fabricated under computer control using a quartz crystal oscillator shielded from the beam to monitor the silicon evaporation and three suppressed Faraday cups to monitor the ion beam current.

D-xylose absorption and disposition in patients with moderately impaired renal function.

D-Xylose kinetics were studied after oral and intravenous administration to 10 patients with impaired renal function, three of whom were being evaluated for intestinal malabsorption. The 0.32 +/- 0.06 L/kg (mean +/- SD) distribution volume of D-xylose in patients with uncomplicated renal impairment was larger than the value of 0.23 +/- 0.04 L/kg that we reported previously for normal subjects (P less than 0.01). Renal clearance was also reduced, averaging 87% of glomerular filtration rate estimated from creatinine clearance, so that the elimination-phase half-life was prolonged to 138 +/- 39 minutes from 75 +/- 11 minutes in normal individuals (P less than 0.01). The 25 gm oral D-xylose dose was 77.4% +/- 14.8% absorbed in the patients with uncomplicated renal impairment, similar to the 69.4% +/- 13.6% absorption reported in normal individuals. However, the absorption half-life was prolonged from 31 +/- 12 minutes in normal subjects to a value of 62 +/- 23 minutes (P less than 0.02). Of the usual clinical indexes of D-xylose absorption, the serum concentration measured 1 hour after the oral dose was best correlated with the extent of D-xylose absorption (r = 0.76; P less than 0.01), and the standard lower normal limit of 0.2 mg/ml was satisfactory.