Impact of biogenic volatile organic compounds on peroxyacetyl nitrate production in the southeast United States

Our atmosphere is arguably the fundamental entity that has made life on Earth possible. Knowledge of the delicate nature of our atmosphere continues to spread as green initiatives promote awareness of human influence on the environment. However, many climate scientists fear that unless immediate mitigation occurs, the reversal of human impact on our planet will be impossible, leading to unknown consequence. Perturbations to natural processes are likely to cause drastic change to the planet as we know it and ultimately result in significant health issues. It is important to push the boundaries of our understanding of atmospheric processes with intent to reduce the impact human activity has already imposed. This work focuses on the production of peroxyacetyl nitrate (PAN), a compound known for its adverse effects on plant life and human health, in two parts; (1) using relative production ratios to calculate relative PAN production using a chemical tracer, and (2) application of an explicit chemical model in simulating relative production of PAN in a southeastern US forest environment. Chapter two examines our current understanding of the isoprene photo-oxidation mechanism particularly in regards to the formation of two peroxyacyl nitrates: PAN and MPAN. A relationship when production is greater than loss processes between MPAN and PAN was found to be relatively constant throughout the experiment with a ratio of MPAN/PAN of 1.5 ± 19% RSD. This relationship can be used in ambient conditions to approximate isoprene contribution to PAN production, since MPAN is formed solely through isoprene oxidation. Absolute concentrations of isoprene nitrates and APNs are found to be significantly oversimulated. This shows an incomplete understanding of the isoprene oxidation mechanism and begs for continued studies to further our understanding of this chemical system. ^ Chapter three applied the observed ratio of MPAN/PAN within the chamber experiment to an ambient calculation to approximate isoprene contribution to PAN production in the SOAS campaign. Results show that an average of 44% ± 16% of PAN production results from the oxidation of isoprene. Further analysis using a 0-D ambient model show isoprene contributes 50-70% to PAN production, which statistically is not different from calculations using MPAN/PAN ratio from chamber experimentation. ^ Chapter four reflects on the results of this study to provide insight to the future of the field. Suggestions for future studies to improve understanding of the PAN mechanism are presented, as well as suggestions for future ambient modeling with a transport model

Assessment of Benthic Habitat Quality in Lower Green Bay, Lake Michigan with Special Regard to Potential Hexagenia Recolonization

With environmental remediation in the Great Lakes, Hexagenia have recovered or are recovering in systems from which they were once extirpated. An active Hexagenia recovery does not appear to be taking place in lower Green Bay. This study first examines the highly fluidized nature of lower Green Bay sediment as a possible cause for their lack of recovery due to nymphs’ potential inability to construct and maintain burrows essential to the completion of their life cycles. Hexagenia bilineata nymphs collected from the Upper Mississippi River were distributed into oxygenated aquaria containing substrates from lower Green Bay or the Upper Mississippi River collection site. Fluidized lower Green Bay sediment did not appear to hinder H. bilineata survival, growth, production, or biomass turnover in a laboratory setting. These metrics were, in several cases, greater in lower Green Bay substrates compared to control substrates from the nymph collection site. Hexagenia egg hatch and young nymph survival in lower Green Bay, tested in situ by artificially stocking eggs collected from adults emerged from western Lake Erie, were shown to be possible, as nine live nymphs ranging from 2-7 mm were recovered near egg stocking sites within one year of stocking. Additionally, meiobenthos, a group suggested to respond negatively to organic pollution, were sampled at several lower Green Bay sites. Densities of Ostracoda, Copepoda, and total meiobenthos, as well as taxon (order) diversity (Simpson’s Index, Shannon-Wiener Index, richness, and evenness) were compared between sites within and outside the Lower Green Bay and Fox River Area of Concern (AOC). Results showed that densities and diversity were not significantly lower within the AOC (p \u3c 0.05). Densities were often greater at sites within the AOC, and diversity was relatively consistent between sites. Overall, the results of this study may suggest potentially higher benthic habitat quality in lower Green Bay than was initially expected

MEMS Deformable Mirrors for Space-Based High-Contrast Imaging

Micro-Electro-Mechanical Systems (MEMS) Deformable Mirrors (DMs) enable precise wavefront control for optical systems. This technology can be used to meet the extreme wavefront control requirements for high contrast imaging of exoplanets with coronagraph instruments. MEMS DM technology is being demonstrated and developed in preparation for future exoplanet high contrast imaging space telescopes, including the Wide Field Infrared Survey Telescope (WFIRST) mission which supported the development of a 2040 actuator MEMS DM. In this paper, we discuss ground testing results and several projects which demonstrate the operation of MEMS DMs in the space environment. The missions include the Planet Imaging Concept Testbed Using a Recoverable Experiment (PICTURE) sounding rocket (launched 2011), the Planet Imaging Coronagraphic Technology Using a Reconfigurable Experimental Base (PICTURE-B) sounding rocket (launched 2015), the Planetary Imaging Concept Testbed Using a Recoverable Experiment - Coronagraph (PICTURE-C) high altitude balloon (expected launch 2019), the High Contrast Imaging Balloon System (HiCIBaS) high altitude balloon (launched 2018), and the Deformable Mirror Demonstration Mission (DeMi) CubeSat mission (expected launch late 2019). We summarize results from the previously flown missions and objectives for the missions that are next on the pad. PICTURE had technical difficulties with the sounding rocket telemetry system. PICTURE-B demonstrated functionality at >100 km altitude after the payload experienced 12-g RMS (Vehicle Level 2) test and sounding rocket launch loads. The PICTURE-C balloon aims to demonstrate 10(-7) contrast using a vector vortex coronagraph, image plane wavefront sensor, and a 952 actuator MEMS DM. The HiClBaS flight experienced a DM cabling issue, but the 37-segment hexagonal piston-tip-tilt DM is operational post-flight. The DeMi mission aims to demonstrate wavefront control to a precision of less than 100 nm RMS in space with a 140 actuator MEMS DM.DARPA; NASA Space Technology Research FellowshipOpen Access JournalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Medial collateral ligament injuries of the knee: current treatment concepts

The medial collateral ligament is one of the most commonly injured ligaments of the knee. Most injuries result from a valgus force on the knee. The increased participation in football, ice hockey, and skiing has all contributed to the increased frequency of MCL injuries. Prophylactic knee bracing in contact sports may prevent injury; however, performance may suffer. The majority of patients who sustain an MCL injury will achieve their pre-injury activity level with non-operative treatment alone; however, those with combined ligamentous injuries may require acute operative care. Accurate characterization of each aspect of the injury will help to determine the optimum treatment plan

Importance of biogenic volatile organic compounds to acyl peroxy nitrates (APN) production in the southeastern US during SOAS 2013

Gas-phase atmospheric concentrations of peroxyacetyl nitrate (PAN), peroxypropionyl nitrate (PPN), and peroxymethacryloyl nitrate (MPAN) were measured on the ground using a gas chromatograph electron capture detector (GC-ECD) during the Southern Oxidants and Aerosols Study (SOAS) 2013 campaign (1 June to 15 July 2013) in Centreville, Alabama, in order to study biosphere&ndash;atmosphere interactions. Average levels of PAN, PPN, and MPAN were 169, 5, and 9&thinsp;pptv, respectively, and the sum accounts for an average of 16&thinsp;% of NOy during the daytime (10:00 to 16:00 local time). Higher concentrations were seen on average in air that came to the site from the urban NOx sources to the north. PAN levels were the lowest observed in ground measurements over the past two decades in the southeastern US. A multiple regression analysis indicates that biogenic volatile organic compounds (VOCs) account for 66&thinsp;% of PAN formation during this study. Comparison of this value with a 0-D model simulation of peroxyacetyl radical production indicates that at least 50&thinsp;% of PAN formation is due to isoprene oxidation. MPAN has a statistical correlation with isoprene hydroxynitrates (IN). Organic aerosol mass increases with gas-phase MPAN and IN concentrations, but the mass of organic nitrates in particles is largely unrelated to MPAN.</p

Astrometric accelerations as dynamical beacons : discovery and characterization of HIP 21152 B, the First T-dwarf companion in the Hyades * * Based in part on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.

Benchmark brown dwarf companions with well-determined ages and model-independent masses are powerful tools to test substellar evolutionary models and probe the formation of giant planets and brown dwarfs. Here, we report the independent discovery of HIP 21152 B, the first imaged brown dwarf companion in the Hyades, and conduct a comprehensive orbital and atmospheric characterization of the system. HIP 21152 was targeted in an ongoing high-contrast imaging campaign of stars exhibiting proper-motion changes between Hipparcos and Gaia, and was also recently identified by Bonavita et al. (2022) and Kuzuhara et al. (2022). Our Keck/NIRC2 and SCExAO/CHARIS imaging of HIP 21152 revealed a comoving companion at a separation of 0.″37 (16 au). We perform a joint orbit fit of all available relative astrometry and radial velocities together with the Hipparcos-Gaia proper motions, yielding a dynamical mass of 24−4+6MJup , which is 1–2σ lower than evolutionary model predictions. Hybrid grids that include the evolution of cloud properties best reproduce the dynamical mass. We also identify a comoving wide-separation (1837″ or 7.9 × 104 au) early-L dwarf with an inferred mass near the hydrogen-burning limit. Finally, we analyze the spectra and photometry of HIP 21152 B using the Saumon & Marley (2008) atmospheric models and a suite of retrievals. The best-fit grid-based models have f sed = 2, indicating the presence of clouds, T eff = 1400 K, and logg=4.5dex . These results are consistent with the object’s spectral type of T0 ± 1. As the first benchmark brown dwarf companion in the Hyades, HIP 21152 B joins the small but growing number of substellar companions with well-determined ages and dynamical masses

Auditory Implicit Learning, and Its Transfer to and from Visual Implicit Learning

Reber and others have shown that the passive learning of synthetic grammars ("implicit learning") is a robust phenomenon when visual stimulus materials are employed. It was the main aim of this study to discover if the same effects occur in the auditory modality, and then to determine if such learning can be transferred from the visual to the auditory mode, and vice versa. In the present study, first, the standard effect was replicated with visual material (Experiment I). Second the effect was also shown to occur when the same material was presented to the auditory modality (Experiment II). It was then shown that implicitly learned material can be transferred from the visual to the auditory modality (Experiment III) and from the auditory to the visual modality (Experiment IV). The implications of the results are discussed with respect to the debate about the "abstractness" or "concreteness" of the mental representation of the material learned

California Gull Predator Management and Reproductive Success of Endangered California Least Terns in the San Francisco Bay, California

Gull predation is known to be an important source of egg and chick mortality for many waterbirds and can have severe impacts on recovery efforts for special status species. We evaluated the effectiveness of California gull management and removal by monitoring tern hatching and fledgling success annually. From 2005 to 2011, nesting success was monitored at a newly established California least tern colony at Hayward Regional Shoreline in San Francisco Bay. No gull management was undertaken prior to 2007. California gulls were the most abundant aerial predator (97%). We recorded 3,769 predatory gull-tern interactions and presumptive take of 26 tern eggs and 23 chicks. Although gull predatory behavior did not change statistically, gull management efforts resulted in significantly improved tern breeding success (measured by number of nests, eggs, chicks, and fledglings). From 2007 to 2011, this colony produced a total of 242 successful nests and 291 fledglings, an average nesting density of 196 nests per ha, and an average of 1.07 fledglings per breeding pair. We discuss difficulties of lethal control of predators, and suggest the importance of human presence for reducing gull predation at the site