1925 research outputs found
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Thermal and radiolytic processing of astrophysical ice analogs
Get PDFVolatile molecules (water (H2O), carbon dioxide (CO2), methane (CH4), hydrogen sulfide (H2S), etc.) present in astrophysical environments condense as ices onto surfaces as large as planetary bodies, and as small as interstellar dust grains. Once condensed, these ices are exposed to both ionizing radiation and thermal processing, which alters their chemical history. To understand the distribution of molecular ices in the solar system and the interstellar medium (ISM), determine reaction pathways to complex molecules in the condensed phase, and interpret spectral data from observational, mission, and modeling studies, it is fundamental to describe the processes that alter molecular ices at low temperatures and pressures.
Here I present experimental studies characterizing these astrophysically-relevant ices and several of the radiolytic and thermal processes that alter these ices. Experiments are performed in a new ultra-high vacuum chamber in the Processes Environments and Astrochemistry on Extraterrestrial Surfaces (PEAXS) Laboratory at Northern Arizona University (NAU), which was constructed in partial fulfillment of this dissertation.
Charged particle bombardment of H2O ice surfaces simultaneously produces radiolytic products and sputters material, providing source material for the tenuous atmospheres around icy satellites, including Europa. We measure the total sputtering yield, or number of ejected molecules per incident ion, for low energy argon ions, analogous to the cold, heavy ion population within the magnetosphere of Jupiter, at temperatures relevant to Europa. We find that current theoretical sputtering models over predict our empirical radiolytic oxygen sputtering yields, and consequently the contribution of sputtered molecular oxygen (O2) due to the cold, heavy magnetospheric ions that irradiate Europa.
The observational absence of the stable low temperature phase of H2O ice, microporous amorphous solid water (ASW), in the outer solar system and ISM is surprising given that temperatures should favor the formation of microporous ASW during ambient condensation. However, we demonstrate that energetic electrons efficiently compact amorphous ice, destroying porosity and internal surface area. We find that microporous ASW should only be expected in the youngest ices in interstellar molecular clouds. To enable future detection of microporous ASW using the James Webb Space Telescope (JWST), we identify several new near-infrared (NIR) features indicative of microporous ASW and demonstrate how they may also probe, the currently elusive homonuclear molecules.
Thermally-driven chemical reactions within astrophysical ices receive significantly less attention than radiation-driven chemistry due to the low temperatures and minimal diffusion associated with astrophysical ices. However, we find several instances of thermally-driven oxidation reactions that occur at temperatures as low as 70 K. We demonstrate that a reaction occurs in ice mixtures of H2S, ozone (O3), and H2O producing sulfur dioxide (SO2), sulfur anions, and O2 at low temperatures, and hydrated sulfuric acid at high temperatures. This reaction is consistent with the observed hemispheric separation of sulfur species and radiolytically-produced oxidants on the Jovian satellites. We also demonstrate that a reaction occurs within ammonia (NH3), O3, and H2O ice mixtures that produces the nitrate ion, which is thermally stable as ammonium nitrate salt at high temperatures. Ammonium nitrate exhibits several NIR spectral features that may be consistent with the observed 2 μm features on several icy solar system worlds, including Charon, Miranda, and Enceladus
Learning from the past, planning for the future: experience-driven insights into management, climate adaptation, and fire adaptation on the Colorado plateau
Get PDFABSTRACT
Current adaptation strategies utilized by federal, state, and local land management agencies face a great deal of challenges. Ecosystems have and will continue to undergo transformations due to ecological stressors. Natural resource managers have experienced varying degrees of wildfire and drought intensification. Findings from interviews conducted with over 37 natural resource managers from federal, state, and local agencies across the Colorado Plateau of the Western U.S. are discussed and analyzed. Primary takeaways from these interviews include discussions with respondents related to ecological stressors, ecosystem response, strategies and decision-making related to drought and wildfire, primary barriers and limitations, perceptions surrounding adaptation, facilitation and implementation of adaptation, and identification of needs to support effective adaptive management. Results from a survey of managers and decision-makers across the Southwest based on the insights and perspectives gathered in interviews are discussed. Several key findings include: 86% of participants citing lack of resources as the primary limiting factor for effective management, 89% of participants reporting that disturbances are happening at scales and timeframes outside of what managers perceive as “normal,” and that 63% of participants found that ecosystems have been substantially or completely stressed by ecological changes including drought, wildfire, and/or climate change impacts. This study concludes that for adaptation to be an effective management practice, there needs to be greater consensus among managers surrounding the meaning and application of the term.
Key Words: climate adaptation, ecosystem stress and transformation, drought, wildfire, climate change, resilience, wilderness, southwest, public lands, natural resource managemen
Tau of doors: footprints of the past
Get PDFT-shaped doors are an enigmatic architectural feature. These features were built in the US Southwest and Mexican Northwest (SW/NW) first at Chaco Canyon around 1020 CE, then expanding throughout the region. T-shaped doors interest archaeologists because of their apparent sudden appearance and potential connection to structures in Mesoamerica. Lekson (2015) has used these features in his argument for the “Chaco Meridian,” a singular social and political group that began at Chaco and later migrated to two monumental sites along a north-south meridian in the SW/NW, first Aztec, New Mexico, then Paquimé, Chihuahua. His argument is bolstered by a perceived scarcity of T-shaped doors outside of this north-south corridor. T-shaped doors do occur outside that corridor in what is now Arizona but have not been systematically identified and counted prior to this research. Callis (2021) has further argued T-shaped doors originate in Mesoamerica because of the similarity of Maya symbols to the T-shape in the SW/NW. This paper addresses the following research questions. What are T-shaped doors? Where do T-shaped doors occur in Arizona? Is there a connection between the Chaco Canyon and Arizona T-shaped doors? To address these questions, I created a data set to systematically identify and count T-shaped doors in Arizona. Based on the following research, T-shaped doors in Arizona do not coincide with Lekson’s and Callis’s theories, and instead Bernardini’s Indigenous Hopi framework as presented in Becoming Hopi (2021) is a far better explanation of this enigmatic feature
Is binarity necessary for the evolution of massive stars to the luminous blue variable and Wolf-Rayet stages?
No full textThe fundamental question in massive star evolution is how important binarity is in their evolution. Luminous blue variables (LBVs) and Wolf-Rayet (WR) stars are the last phases of evolution for the most massive stars and whether a close companion star is required for their evolution and what their relation is to each other is heavily debated. In single-star evolution, the most massive stars have a short-lived transitionary phase as LBVs before evolving into WR stars. In the binary evolution, LBVs are mass gainers and WRs undergo mass-loss via Roche Lobe overflow. To shed light on this fundamental question, we analyze the spatial distribution of LBVs compared to their progenitor O-type stars and descendant WR stars. We found the LBVs have a spatial distribution similar to the other massive star samples, meaning that a close companion star is not required in their formation. For WR stars, we model the near-infrared, optical, and ultraviolet spectrum of carbon-rich (WC-type) and oxygen-rich (WO-type) WR stars to determine their physical parameters, which can be compared to those predicted by the Geneva single-star and BPASS binary evolutionary models. The WC- and WO- type stars have successes and problems with both types of evolution, possibly also indicating that they could have evolved as single stars. Through this process, the WOs were found to be further evolved than the WCs confirming that they are the last ``hurrah'' of massive star evolution. Overall, massive stars may not require a close companion star to form and evolve
Power system operation with high penetration of electric vehicles and renewable energy
Get PDFThis dissertation document explores the potential impacts of integrating electric vehicles (EVs) and variable renewable energies (VRE) on power system operation. EV penetration scenarios of the light-duty vehicle fleet of 10%, 20%, and 30% are considered in the RTS-GMLC test system. RTS-GMLC is an updated version of the IEEE RTS-96 test system, allowing for modern inter-hour or real-time market modeling; it has a generation fleet with characteristics comparable to current power systems used in the western United States, and VRE penetration equal to 34% of annual energy consumption. The impacts of EVs are investigated during the annual peak in the summer and during four weeks of the year in which high VRE combined with low loads lead to overgeneration. Uncoordinated and coordinated EV charging scenarios are considered. In the uncoordinated scenario, charging is undertaken at the convenience of the EV owners, and this is modeled using data from the Idaho National Laboratory's EV Project. To create an uncoordinated charging load profile, the parameters of importance are the number of vehicles, charger type, battery capacity, availability for charging, and battery beginning and ending states of charge. Beta distributions were found to be the most appropriate distribution for statistically modeling the initial and final state of charge (SoC) of vehicles in an EV fleet. A Monte Carlo technique was implemented by sampling the charging parameters of importance to create an uncoordinated charging load time series. Coordinated charging is modeled as a controllable load using an "aggregator" model, wherein EV charging is scheduled to minimize operating costs while meeting the daily charging requirements subject to EV availability and charging constraints. To capture the impacts, the production cost model (PCM) Power System Optimizer (PSO), created by Polaris, is employed. The model uses load and VRE forecasts as part of a multiple-planning cycle rolling horizon approach to commit realistic generating units based on their start-up characteristics, while preserving the flexibility of units with short start-up times and EV charging. At each EV penetration level, the uncoordinated charging costs were higher than the coordinated ones. At 10% EV penetration, the uncoordinated charging cost per vehicle was four times higher than with coordinated charging during a low load week in February. During a high-VRE, low-load week in April, with uncoordinated EV charging at 30% penetration (3% energy penetration), the peak load increased as much as 27%. Using coordinated EV charging, the EV load shifts to hours with low prices, coincident with either low load, high VRE, or both. Furthermore, coordinated charging reduces the curtailment of PV by as much as nine times during the winter operation season, and the curtailment of wind generation by more than half during the summer operation season, compared to the scenarios with no EVs and uncoordinated EV charging. Using multiple planning cycles, load and VRE forecasts, and a “look ahead” period during scheduling and dispatching, units were judged to be important in creating and utilizing the flexibility of coordinated EV charging
Stratigraphy, age, and structural evolution of South Dome Rock Mountains basin, southeast Blythe basin, Arizona
No full textThe Colorado River extensional corridor, an area affected by large-magnitude Basin and Range extension and overprinted by younger transtensional deformation, provides an opportunity to study the inboard deformation associated with the inception and evolution of the Pacific-North America plate boundary. Earlier work shows that not all post-middle Miocene dextral shear predicted to have occurred across the Pacific-North America plate boundary east of the San Andreas fault is accounted for in the Colorado River extensional corridor region. Some or all of the unaccounted dextral shear may have occurred in the Blythe pull-apart basin, a sedimentary basin in the Colorado River extensional corridor that has been interpreted as a fault-bounded pull-apart basin related to the inboard part of the Pacific-North America plate boundary. At the southeast margin of the Blythe pull-apart basin, geologic mapping coupled with my new geochronologic, stratigraphic, and structural analysis of the south Dome Rock Mountains basin and related fault systems suggest (1) the older fluvial section of the basin formed between ~35 and ~23.7 Ma, before regional Basin and Range extension; (2) a series of ~23.7–22 Ma volcanic rocks record Basin and Range volcanism in the area; (3) the upper basin formed above the hanging wall of the southwest-dipping listric south Dome Rock Mountains fault from 22–12.8 Ma; and (4) the basin was inverted and deformed by <12.8 Ma dextral shear
Conspecific brood parasitism: reevaluating a bird’s-eye view
Get PDFConspecific brood parasitism, also known as intraspecific brood parasitism, is characterized by individuals depositing eggs into the established nests of others of the same species. One of the most widely held explanations for this behavior is that the brood parasites “make the best of a bad job,” or the BOBJ hypothesis, put forward by Dawkins (1980). That is, they are able to reproduce successfully via parasitism and persist within the population despite having fitness that is less than the average of the non-parasitic, nesting individuals. We show that brood parasitism in modern birds may instead represent a conditional polymorphism that persists because nest loss, social interactions, or other environmental influences may prevent a fraction of the population from rearing offspring within their own nests. When the fitness of unsuccessful females is included in the form of a “zero class” along with the fitness of successful females, calculations of average fitness reveal that the fitness of parasitic and non-parasitic females is equivalent. These conditions are necessary and sufficient to maintain quantitative genetic variation underlying the tendency to become a brood parasite. These findings suggest that the BOBJ hypothesis as the de facto interpretation of brood parasitism should be re-examined and open the door to new understandings of the relationship between conspecific brood parasitism (CBP) and population ecology. A potential next step in this re-examination of CBP is to look to the ancestral lineage of modern birds. Like many other aspects of modern bird biology, CBP as a polymorphism in the breeding population may have a dinosaurian origin. Using a published literature review by Yom-Tov (2001) which identifies the nest characteristics of modern birds that engage in CBP, we suggest non-avian dinosaur taxa that could be viewed in the context of potential CBP
Developing analytical chemical analysis procedures for craft beers and their adjunct ingredients
Get PDFThroughout history, commercially available beer has remained unregulated relative to other food and beverage products. At present, the brewing industry is transitioning from minimal oversight to regulations that are more in line with other commercial beverages. Mounting pressure from regulatory bodies and industry rivals has created considerable demand for better QA/QC procedures pertaining to beer. One topic of growing interest and concern is the heavy metal content of finished beer. There are currently no effective regulations on the heavy metal content of commercially available beer. Recent research has indicated the presence of previously unknown heavy metal contaminant exposure routes in the industry.
The raw materials used to make beer are mostly agricultural goods. Therefore, they are potential facilitators of common farm contaminants such as living organisms, fertilizers, and pesticides. The brewing process through which raw materials become beer is one that involves metal tanks, acidic conditions, and elevated temperatures. These conditions are ideal for the leaching of metal contaminants into beer. Additionally, the growing trend of adding unique, unprecedented ingredients to process beer has resulted in alarming outcomes. These factors are all quite worrisome, as it is the responsibility of brewers to ensure that consumers are not chronically ingesting contaminants such as trace metals. The industry needs methods that ensure proper quality control and consumer safety. Optimized analytical grade analysis procedures would be a significant boon to this effort.
Research into the viability of two procedures was conducted: (1) the destructive analysis of trace metals within beer products via spectroscopic methods and (2) a nondestructive approach to quantifying and assessing the in-solution stability of unique drug compound ingredients over time. An adequate digestion protocol would enable analysts to prepare a sample for elemental analysis, without losing analyte or introducing heavy metal contaminants. Applying such methods to beer is a difficult task. Beer is a loose term that applies to a complex organic sample matrix with distinct compositions and infinite varietals. Even consecutive executions of the same brewing processes can produce batches with significant chemical differences. This presentation will focus on the development of analytical sample digest methods that overcome these hurdles and enable brewers and chemists alike to probe their beer with rigor and reproducibility.
Role Play
No full textThis collection, titled Role Play, explores the cultural impact of queer identity and community, both historically and through the modern lens of a speaker ‘raised cisgender and straight’, while also combatting stereotypes associated with binary gender roles. It attempts to do so in two main ways: through brutal honesty, and through gratitude and grace. While the speaker discovers themselves through evolving gender and sexual identities, the collection simultaneously critiques heteronormative society for its historically unforgiving discrimination of the queer community and unrealistic expectations for concepts like ‘normalcy’ and ‘belonging’. Our queerness has violent roots, and we bloom anyway. The speaker, occasionally referred to as “the writer”, does not shy away from the reader’s belonging and relatability in the collection. The reader is taken on an emotional journey through the layers of a traumatized community; first, we see the hurt and armor, the defensive hard shell that eventually gets cracked, and the poems with softer quality, with gratitude and growth, prevail in the second half of the manuscript. This arrangement is realistic to a common trajectory for healing. The pain must be acknowledged before the growth can take its place
Fat outside: an arts-based and narrative inquiry approach to building fat-positive community and connection in nature
No full textStudies have shown that there are direct correlations between exposure to nature and improved self-perception of body image, as well as reduced stress levels (Kondo, Jacoby and Smith, 2018; Stieger, Archinger, and Swami, 2020). Those who face fat discrimination or anti-fat bias are often barred from enjoying the benefits of nature and outdoor spaces, whether because of others’ comments on their body size, accessibility to gear/space, or lack of safety, etc. This research explored the question: “How might intentional fat-positive spaces outdoors encourage fat people to build community in ways that connect them to themselves, others, and natural spaces?” Using narrative inquiry and arts-based research methodologies, I collected data from four participants through individual interviews, a set of two art pieces, and a group hike event with a focus group discussion and follow-up survey. I analyzed the data based on emergent themes and compared results for connection to self, others, and nature in the context of two theoretical frameworks: intersectional, feminist fat liberation and political ecology of the body.
The goal of the study was to increase inclusivity, access, and belonging for fat people in the outdoors, while contributing narratives to the growing field of fat studies. Key findings showed that throughout the fat-positive group hike event, participants experienced reduced anxiety and increased comfortability compared to when they were outdoors alone. The art pieces illustrated an overall reduced focus on negative body image and an increase in mindfulness outdoors. These findings suggested that Fat Outside participants developed a beneficial fat-positive community, resulting in deeper and more positive connections to themselves, others, and nature. Future research may further explore how fat outdoor groups impact community long-term and shift or maintain fat people’s views of themselves, society, and the outdoors