25 research outputs found
High resolution charge-exchange spectroscopic measurements of aluminum impurity ions in a high temperature plasma
Charge-exchange recombination spectroscopy, which is generally used to measure low-Z impurities in fusion devices, has been used for measuring Al+11 and Al+13 impurities in the Madison Symmetric Torus reversed field pinch. To obtain the impurity ion temperature, the experimental emission spectrum is fitted with a model which includes fine structure in the atomic transition. Densities of these two ionization states, calculated from charge-exchange emission brightness, are used in combination with a collisional radiative model to estimate the abundance of all other charge states of aluminum in the plasma and the contribution of aluminum to the effective ionic charge of the plasma
Emissions of volatile organic compounds (VOCs) from concentrated animal feeding operations (CAFOs): chemical compositions and separation of sources
Concentrated animal feeding operations (CAFOs) emit a large number of
volatile organic compounds (VOCs) to the atmosphere. In this study, we
conducted mobile laboratory measurements of VOCs, methane (CH4) and
ammonia (NH3) downwind of dairy cattle, beef cattle, sheep and chicken
CAFO facilities in northeastern Colorado using a hydronium ion
time-of-flight chemical-ionization mass spectrometer (H3O+
ToF-CIMS), which can detect numerous VOCs. Regional measurements of CAFO
emissions in northeastern Colorado were also performed using the NOAA WP-3D
aircraft during the Shale Oil and Natural Gas Nexus (SONGNEX) campaign.
Alcohols and carboxylic acids dominate VOC concentrations and the reactivity
of the VOCs with hydroxyl (OH) radicals. Sulfur-containing and phenolic
species provide the largest contributions to the odor activity values and
the nitrate radical (NO3) reactivity of VOC emissions, respectively.
VOC compositions determined from mobile laboratory and aircraft measurements
generally agree well with each other. The high time-resolution mobile
measurements allow for the separation of the sources of VOCs from different
parts of the operations occurring within the facilities. We show that the
emissions of ethanol are primarily associated with feed storage and
handling. Based on mobile laboratory measurements, we apply a multivariate
regression analysis using NH3 and ethanol as tracers to determine the
relative importance of animal-related emissions (animal exhalation and
waste) and feed-related emissions (feed storage and handling) for different
VOC species. Feed storage and handling contribute significantly to emissions
of alcohols, carbonyls, carboxylic acids and sulfur-containing species.
Emissions of phenolic species and nitrogen-containing species are
predominantly associated with animals and their waste
Impact of primary kidney disease on the effects of empagliflozin in patients with chronic kidney disease: secondary analyses of the EMPA-KIDNEY trial
Background: The EMPA KIDNEY trial showed that empagliflozin reduced the risk of the primary composite outcome of kidney disease progression or cardiovascular death in patients with chronic kidney disease mainly through slowing progression. We aimed to assess how effects of empagliflozin might differ by primary kidney disease across its broad population. Methods: EMPA-KIDNEY, a randomised, controlled, phase 3 trial, was conducted at 241 centres in eight countries (Canada, China, Germany, Italy, Japan, Malaysia, the UK, and the USA). Patients were eligible if their estimated glomerular filtration rate (eGFR) was 20 to less than 45 mL/min per 1·73 m2, or 45 to less than 90 mL/min per 1·73 m2 with a urinary albumin-to-creatinine ratio (uACR) of 200 mg/g or higher at screening. They were randomly assigned (1:1) to 10 mg oral empagliflozin once daily or matching placebo. Effects on kidney disease progression (defined as a sustained ≥40% eGFR decline from randomisation, end-stage kidney disease, a sustained eGFR below 10 mL/min per 1·73 m2, or death from kidney failure) were assessed using prespecified Cox models, and eGFR slope analyses used shared parameter models. Subgroup comparisons were performed by including relevant interaction terms in models. EMPA-KIDNEY is registered with ClinicalTrials.gov, NCT03594110. Findings: Between May 15, 2019, and April 16, 2021, 6609 participants were randomly assigned and followed up for a median of 2·0 years (IQR 1·5–2·4). Prespecified subgroupings by primary kidney disease included 2057 (31·1%) participants with diabetic kidney disease, 1669 (25·3%) with glomerular disease, 1445 (21·9%) with hypertensive or renovascular disease, and 1438 (21·8%) with other or unknown causes. Kidney disease progression occurred in 384 (11·6%) of 3304 patients in the empagliflozin group and 504 (15·2%) of 3305 patients in the placebo group (hazard ratio 0·71 [95% CI 0·62–0·81]), with no evidence that the relative effect size varied significantly by primary kidney disease (pheterogeneity=0·62). The between-group difference in chronic eGFR slopes (ie, from 2 months to final follow-up) was 1·37 mL/min per 1·73 m2 per year (95% CI 1·16–1·59), representing a 50% (42–58) reduction in the rate of chronic eGFR decline. This relative effect of empagliflozin on chronic eGFR slope was similar in analyses by different primary kidney diseases, including in explorations by type of glomerular disease and diabetes (p values for heterogeneity all >0·1). Interpretation: In a broad range of patients with chronic kidney disease at risk of progression, including a wide range of non-diabetic causes of chronic kidney disease, empagliflozin reduced risk of kidney disease progression. Relative effect sizes were broadly similar irrespective of the cause of primary kidney disease, suggesting that SGLT2 inhibitors should be part of a standard of care to minimise risk of kidney failure in chronic kidney disease. Funding: Boehringer Ingelheim, Eli Lilly, and UK Medical Research Council
Solid liner implosions on Z for producing multi-megabar
Density fluctuation measurements by far-forward collective scattering in the MST reversed-field pinch Rev. Sci. Instrum. 83, 10E302 (2012) Mapping return currents in laser-generated Z-pinch plasmas using proton deflectometry Appl. Phys. Lett. 100, 203505 (2012) Solid liner implosions on Z for producing multi-megabar, shockless compressions Phys. Plasmas 19, 056310 (2012) Stagnation of a gas puff Z pinch Phys. Plasmas 19, 032705 (2012) Additional information on Rev. Sci. Instrum. An advanced neutral particle analyzer (ANPA) capable of simultaneously measuring hydrogen and deuterium ions of energies up to 45 keV has recently been developed for use on the Madison Symmetric Torus. The charge-to-mass separation allows for separate analysis of bulk deuterium ions and hydrogen ions injected with a 1 MW, 25 keV neutral beam. Orientation of the ANPA allows sampling of different regions of ion velocity space; a radial viewport favors collection of ions with high v ⊥ /|v| while a recently installed tangential viewport favors ions with high v || /|v|, such as those from the core-localized fast ion population created by the neutral beam. Signals are observed in the ANPA's highest energy channels during periodic magnetic reconnection events, which are drivers of anisotropic, non-Maxwellian ion energization in the reversed-field pinch. ANPA signal strength is dependent on the background neutral density, which also increases during magnetic reconnection events, so careful analysis must be performed to identify the true change in the ion distribution. A Monte Carlo neutral particle tracing code (NENE) is used to reconstruct neutral density profiles based on D α line emission, which is measured using a 16-chord filtered photodiode array
Interannual variability of ammonia concentrations over the United States: sources and implications
The variability of atmospheric ammonia (NH<sub>3</sub>), emitted largely from
agricultural sources, is an important factor when considering how inorganic
fine particulate matter (PM<sub>2.5</sub>) concentrations and nitrogen cycling are
changing over the United States. This study combines new observations of
ammonia concentration from the surface, aboard aircraft, and retrieved by
satellite to both evaluate the simulation of ammonia in a chemical transport
model (GEOS-Chem) and identify which processes control the variability of
these concentrations over a 5-year period (2008–2012). We find that the
model generally underrepresents the ammonia concentration near large source
regions (by 26 % at surface sites) and fails to reproduce the extent of
interannual variability observed at the surface during the summer (JJA).
Variability in the base simulation surface ammonia concentration is dominated
by meteorology (64 %) as compared to reductions in SO<sub>2</sub> and NO<sub><i>x</i></sub>
emissions imposed by regulation (32 %) over this period. Introduction of
year-to-year varying ammonia emissions based on animal population, fertilizer
application, and meteorologically driven volatilization does not
substantially improve the model comparison with observed ammonia
concentrations, and these ammonia emissions changes have little effect on the
simulated ammonia concentration variability compared to those caused by the
variability of meteorology and acid-precursor emissions. There is also little
effect on the PM<sub>2.5</sub> concentration due to ammonia emissions variability
in the summer when gas-phase changes are favored, but variability in
wintertime emissions, as well as in early spring and late fall, will have a
larger impact on PM<sub>2.5</sub> formation. This work highlights the need for
continued improvement in both satellite-based and in situ ammonia
measurements to better constrain the magnitude and impacts of spatial and
temporal variability in ammonia concentrations
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Emissions of volatile organic compounds (VOCs) from concentrated animal feeding operations (CAFOs): chemical compositions and separation of sources
Concentrated animal feeding operations (CAFOs) emit a large number of
volatile organic compounds (VOCs) to the atmosphere. In this study, we
conducted mobile laboratory measurements of VOCs, methane (CH4) and
ammonia (NH3) downwind of dairy cattle, beef cattle, sheep and chicken
CAFO facilities in northeastern Colorado using a hydronium ion
time-of-flight chemical-ionization mass spectrometer (H3O+
ToF-CIMS), which can detect numerous VOCs. Regional measurements of CAFO
emissions in northeastern Colorado were also performed using the NOAA WP-3D
aircraft during the Shale Oil and Natural Gas Nexus (SONGNEX) campaign.
Alcohols and carboxylic acids dominate VOC concentrations and the reactivity
of the VOCs with hydroxyl (OH) radicals. Sulfur-containing and phenolic
species provide the largest contributions to the odor activity values and
the nitrate radical (NO3) reactivity of VOC emissions, respectively.
VOC compositions determined from mobile laboratory and aircraft measurements
generally agree well with each other. The high time-resolution mobile
measurements allow for the separation of the sources of VOCs from different
parts of the operations occurring within the facilities. We show that the
emissions of ethanol are primarily associated with feed storage and
handling. Based on mobile laboratory measurements, we apply a multivariate
regression analysis using NH3 and ethanol as tracers to determine the
relative importance of animal-related emissions (animal exhalation and
waste) and feed-related emissions (feed storage and handling) for different
VOC species. Feed storage and handling contribute significantly to emissions
of alcohols, carbonyls, carboxylic acids and sulfur-containing species.
Emissions of phenolic species and nitrogen-containing species are
predominantly associated with animals and their waste
Evaluation of the accuracy of thermal dissociation CRDS and LIF techniques for atmospheric measurement of reactive nitrogen species
The sum of all reactive nitrogen species (NOy) includes
NOx (NO2 + NO) and all of its oxidized forms, and the
accurate detection of NOy is critical to understanding atmospheric
nitrogen chemistry. Thermal dissociation (TD) inlets, which convert NOy
to NO2 followed by NO2 detection, are frequently used in
conjunction with techniques such as laser-induced fluorescence (LIF) and
cavity ring-down spectroscopy (CRDS) to measure total NOy when set at
> 600 °C or speciated NOy when set at
intermediate temperatures. We report the conversion efficiency of known
amounts of several representative NOy species to NO2 in our TD-CRDS
instrument, under a variety of experimental conditions. We find that the
conversion efficiency of HNO3 is highly sensitive to the flow rate and
the residence time through the TD inlet as well as the presence of other
species that may be present during ambient sampling, such as ozone (O3).
Conversion of HNO3 at 400 °C, nominally the set point used to
selectively convert organic nitrates, can range from 2 to 6 % and may
represent an interference in measurement of organic nitrates under some
conditions. The conversion efficiency is strongly dependent on the operating
characteristics of individual quartz ovens and should be well calibrated
prior to use in field sampling. We demonstrate quantitative conversion of
both gas-phase N2O5 and particulate ammonium nitrate in the TD
inlet at 650 °C, which is the temperature normally used for conversion of
HNO3. N2O5 has two thermal dissociation steps, one at low
temperature representing dissociation to NO2 and NO3 and one at
high temperature representing dissociation of NO3, which produces
exclusively NO2 and not NO. We also find a significant interference from
partial conversion (5–10 %) of NH3 to NO at 650 °C in the
presence of representative (50 ppbv) levels of O3 in dry zero air.
Although this interference appears to be suppressed when sampling ambient
air, we nevertheless recommend regular characterization of this interference
using standard additions of NH3 to TD instruments that convert reactive
nitrogen to NO or NO2
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Evaluation of the accuracy of thermal dissociation CRDS and LIF techniques for atmospheric measurement of reactive nitrogen species
Abstract. The sum of all reactive nitrogen species (NOy) includes NOx (NO2 + NO) and all of its oxidized forms, and the accurate detection of NOy is critical to understanding atmospheric nitrogen chemistry. Thermal dissociation (TD) inlets, which convert NOy to NO2 followed by NO2 detection, are frequently used in conjunction with techniques such as laser induced fluorescence (LIF) and cavity ringdown spectroscopy (CRDS) to measure total NOy when set at > 600 °C, or speciated NOy when set at intermediate temperatures. We report the conversion efficiency of known amounts of several representative NOy species to NO2 in our TD-CRDS instrument, under a variety of experimental conditions. We find that the conversion efficiency of HNO3 is highly sensitive to the flow rate and the residence time through the TD inlet, as well as the presence of other species that may be present during ambient sampling, such as ozone (O3). Conversion of HNO3 at 400 °C, nominally the set point used to selectively convert organic nitrates, can range from 2–6 % and may represent an interference in measurement of organic nitrates under some conditions. The conversion efficiency is strongly dependent on the operating characteristics of individual quartz ovens, and should be well calibrated prior to use in field sampling. We demonstrate quantitative conversion of both gas phase N2O5 and particulate ammonium nitrate in the TD inlet at 650 °C, the temperature normally used for conversion of HNO3. N2O5 has two thermal dissociation steps, one at low temperature representing dissociation to NO2 and NO3, and one at high temperature representing dissociation of NO3, which produces exclusively NO2 and not NO. We also find a significant interference from partial conversion (5–10 %) of NH3 to NO at 650 °C in the presence of representative (50 ppbv) levels of O3 in dry zero air. Although this interference appears to be suppressed when sampling ambient air, we nevertheless recommend regular characterization of this interference using standard additions of NH3 to TD instruments that convert reactive nitrogen to NO or NO2.
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Classical confinement and outward convection of impurity ions in the MST RFP Additional information on Phys. Plasmas Classical confinement and outward convection of impurity ions in the MST RFP a)
Impurity ion dynamics measured with simultaneously high spatial and temporal resolution reveal classical ion transport in the reversed-field pinch. The boron, carbon, oxygen, and aluminum impurity ion density profiles are obtained in the Madison Symmetric Torus [R. N. Dexter et al., Fusion Technol. 19, 131 (1991)] using a fast, active charge-exchange-recombination-spectroscopy diagnostic. Measurements are made during improved-confinement plasmas obtained using inductive control of tearing instability to mitigate stochastic transport. At the onset of the transition to improved confinement, the impurity ion density profile becomes hollow, with a slow decay in the core region concurrent with an increase in the outer region, implying an outward convection of impurities. Impurity transport from Coulomb collisions in the reversed-field pinch is classical for all collisionality regimes, and analysis shows that the observed hollow profile and outward convection can be explained by the classical temperature screening mechanism. The profile agrees well with classical expectations. Experiments performed with impurity pellet injection provide further evidence for classical impurity ion confinement. V C 2012 American Institute of Physics