8413 research outputs found
Sort by
Aquatic Ecosystem Function Under Climate Stress: Linking Hydroclimate Volatility to Biogeochemical Responses in Streams and Lakes
No full textFreshwater ecosystems are undergoing rapid and widespread transformations in response to accelerating and volatile global hydroclimatic change. Hydroclimate refers to the climate-driven dynamics of water availability and movement, shaped by both global and regional atmospheric processes (e.g., evaporation, precipitation) and hydrologic storage (e.g., snowpack, groundwater, surface waters, and vegetation). Climate-driven shifts in hydroclimatic regimes, land-use intensification, and biogeochemical disturbance are altering the structure and function of rivers, lakes, and wetlands across the globe—disrupting their ability to cycle nutrients, carbon, and support biodiversity. In aquatic environments, metabolism (e.g., gross primary production [GPP], ecosystem respiration [ER], and net ecosystem productivity [NEP]) represents a tractable, integrative measure of ecosystem function. Because metabolic rates reflect the balance of autotrophic and heterotrophic processes, they are sensitive to both chronic pressures and episodic disturbances, offering insight into how ecosystems respond to variability in light, temperature, hydrology, and nutrient availability. As hydroclimate volatility increases the frequency and intensity of wet-dry transitions, it becomes increasingly urgent to understand how aquatic metabolism responds across spatial and temporal scales to anticipate shifts in ecosystem resilience and biogeochemical cycling.The three chapters presented here offer novel empirical and theoretical contributions to aquatic ecosystem ecology, focusing on the metabolic consequences of changing hydroclimatic conditions. Chapter one demonstrates how shifts in the timing and magnitude of streamflow in mountain headwater catchments decouple hydrologic and biological processes, whereas wet years reduce GPP and alter nitrogen dynamics—even between neighboring streams with similar morphology. Chapter two expands this case study perspective to the downstream oligotrophic lake, by evaluating how stream inflows influence nearshore metabolic regimes across four different shores in Tahoe, Sierra Nevada, USA. Here we show how GPP or ER differ from drought to wet years depending on hydrologic connectivity across the different nearshore locations. In chapter three we quantified the spatial synchrony in both GPP and ER for 48 unique streams spanning, geographic, land cover, and morphometric gradients to find that local factors such as flow and light mediate spatial synchrony in GPP and ER more strongly than regional climatic drivers. Collectively, these studies highlight that while aquatic ecosystem function is influenced by broad-scale environmental forcing, it can be more strongly mediated by local conditions. By examining aquatic ecosystem metabolism across gradients of connectivity, flow, and climatic variability, this work advances both applied understanding of freshwater vulnerability and theoretical frameworks for scaling carbon fluxes in a changing world
Psychometrics & Utility of a Sexual Misconduct Disclosure Questionnaire and Website
No full textSexual misconduct encompasses illegal and often traumatic, nonconsensual sexual behaviors ranging from privacy breaches to penetration. Sexual misconduct occurs more frequently than the rate it is reported, hindering the survivor’s ability to heal and pursue justice. Due to the adverse mental and physical health effects associated with sexual misconduct, psychological, social, and legal services exist. However, access to these resources is limited and disparate, hindering many people’s ability to feel empowered to pursue prosecution through the formal disclosure process. This study aimed (1) to further psychometrically evaluate the Sexual Misconduct Disclosure Questionnaire (SMDQ) so that it can be used to identify relevant barriers to the formal disclosure process. It also aimed (2) to evaluate the efficacy of a resources website in promoting survivors’ willingness to pursue formal disclosure by providing relevant resources for barriers addressed in the SMDQ. A randomly controlled trial was used to gain information on the test-retest reliability and construct validity of the SMDQ. The efficacy of its associated website was also assessed for its ability to increase knowledge about overcoming barriers. The SMDQ demonstrated strong psychometric properties of construct validity and test-retest reliability, identifying privacy concerns, insufficient evidence, and shame as the most common barriers to disclosure. While the pilot website performed comparably to the control condition, it did not significantly increase willingness to report. These findings highlighted that barriers rarely exist independently and are major challenges requiring reform on the individual and institutional levels. Future research should explore how incorporating standardized tools such as the SMDQ in disclosure processes can promote reporting rates and survivor outcomes
Relationship Between the Lactate Thresholds and Endurance Performance in Trained Runners
No full textThe study explored the relationship between the aerobic threshold (AeT), anaerobic threshold (AnT), and endurance performance in trained runners. A total of 63 participants were tested and 52 were included (38 male, 14 female). They conducted a treadmill graded exercise test (GXT) to determine their AeT and AnT, as well as heart rate and blood lactate levels at each threshold. The participants were categorized into elite (D1 cross-country athletes and professional athletes) and recreational groups, with a minimum of two hours of running per week required for inclusion.The key findings were as follows:
• Significant differences were observed between elite and recreational runners in both speed and heart rate at the AeT and AnT. Specifically, elite athletes had higher speeds and heart rates at both thresholds.
• The percentage difference between AeT and AnT heart rates was significantly lower in the elite group (6.8% ± 2.1%) than the recreational group (8.9% ± 3%), indicating better lactate clearance and metabolic efficiency in elite runners.
The percent difference in heart rate was a valuable metric for comparing elite and recreational runners, with athletes outside the observed range (below 5% or above 9% difference) potentially indicating deficits in training. Above 9% indicating an athlete’s performance may be limited aerobically, while below 5% meaning they are anaerobically deficient, lacking the ability to produce more lactate. These findings suggest that the percentage difference between AeT and AnT heart rates may serve as an additional marker for endurance performance, especially for individualizing training prescriptions, because the percentage difference between threshold heart rates may show training deficits
How interactions with plants influence butterfly responses to environmental stressors: from pathogens to climate change
No full textGlobal insect declines have been reported with increasing fervor from the scientific community as well as the public discourse. The factors contributing to declines are numerous and likely interactive, but the best-documented contributors are habitat loss, pesticide use, climate change, disease, invasive species, and pollution. For Lepidoptera, moths and butterflies, population trajectories are heterogeneous across taxa and geography. Butterflies, superfamily Papilionoidea, are among the most thoroughly studied groups in Lepidoptera due to their popularity and relative ease of identification. Several high-resolution (species-level) long-term monitoring efforts of butterflies have revealed widespread declines across diverse ecosystems. In this dissertation, I focus on a few of the main drivers of butterfly population declines – disease, invasive plants, and climate change, and ask whether butterflies’ relationships with their food plants can increase or decrease their susceptibility to these stressors. My four dissertation projects can be divided conceptually into two major questions: 1) do larval host plants, including exotic hosts, mediate herbivore-pathogen interactions in a specialist caterpillar? and 2) do nectar resources shape butterfly responses to anthropogenic change? Under the first conceptual framework, I used a laboratory rearing experiment, chemical analysis, and molecular viral detection methods to examine the effects of larval host plant species and secondary chemistry on viral transmission, infection intensity, and survival in caterpillars of a North American butterfly species, Euphydryas phaeton (Nymphalidae). Euphydryas phaeton are an appealing study system as they are chemical specialists on host plants containing iridoid glycosides, and have recently incorporated an exotic host plant into their diet. Therefore, they are ideal for investigating the evolution of diet breadth, and the effects of plant defensive chemistry on herbivore fitness and interactions with higher trophic levels.
In my first dissertation project we found that caterpillars utilizing their native host plant had reduced survival when experimentally infected with a viral pathogen, in comparison to those feeding on the exotic host plant, motivating the hypothesis of dietary range expansion driven by pathogen resistance on the novel host. Additionally, I utilized a field study to examine viral prevalence in the gregarious caterpillars of E. phaeton in their natural habitat. I found that the distribution of the virus at the landscape scale occurred with viral “hotspots” or areas with high infection prevalence, and that viral prevalence correlated with underlying host plant chemistry in a manner that was host plant dependent.
For the second major theme, I leveraged large datasets, including a long-term butterfly monitoring program from the Sierra Nevada mountains (Shapiro transect), natural history observations from GBIF, and a three-year intensive survey of nectar plants to better understand the role of floral composition and availability for diversity and population trends of montane butterflies. I found that there is variation in nectar breadth among adult butterflies of the Sierra Nevada, though the majority of species tended towards generalism. Surprisingly, nectar specialists had more positive population trajectories than generalists, indicating a possible fitness cost to generalism in these communities. Additionally, I gathered three years of floral data across six montane sites where long-term butterfly monitoring takes place. I found that butterfly diversity is strongly related to floral diversity, relative to floral abundance, indicating these butterflies are depending on a diverse assemblage of floral resources through the flying season. Additionally, it appears that an extreme heat event in California during the summer of 2024 may have driven advanced butterfly phenology relative to flower phenology, and accounted for reduced abundance and diversity later in the season
AN ANALYSIS OF VISUAL ELEMENTS OF NAVIGATION IN AUGMENTED AND VIRTUAL REALITIES
No full textHuman navigation is a fundamental form of human activity, and with the adventof the technologies of augmented and virtual reality, there is an increase in possible environments requiring navigation and the methods by which environments
are navigated. Many tools and methods appropriate for older navigation contexts
exist, but these may not be applicable or useful in these newer contexts. This work
examines the challenges these contexts pose and provides tools and novel methods
to address them, by focusing on the sense of vision and the navigation elements
that address that sense.
Augmented reality allows for greater precision in path-routing and ease of following directions for the user, but the challenges of localization and the physical
constraints of navigation in the real world must be addressed for the technology to
provide utility to the user. Research into augmented reality navigation suffers from
significant limitations, which are identified in the course of this dissertation. An
effort to support the development of augmented reality solutions is also included
in the form of a software tool for creating depth maps from sensors of augmented
reality devices.
Virtual reality environments can be a struggle to navigate within due to cybersickness, leading to a research focus on locomotion techniques. These locomotion
techniques can be improved by creative modifications due to the presence of fewer
physical constraints than exist in the real world, and this dissertation presents several strategies to improve a classic locomotion technique: teleportation.
Overall, the goal of the work presented here is to improve the user experience of
navigating, both in virtual and real contexts, by analyzing and contributing visual
navigation strategies where they are lacking in the current field of research
2023 Nevada Middle School Youth Risk Behavior Survey (YRBS): Positive Childhood Experiences (PCEs) Special Report
No full textThis surveillance project was partially supported by a grant from the Centers for Disease Control and Prevention (CDC-PS18-1807). Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the CDC. Supplemental funding was also provided by the Nevada Division of Public and Behavioral Health. This report was supported by funds made available from the Centers for Disease Control and Prevention under award #NU81CE002075 Essentials for Childhood: Preventing Adverse Childhood Experiences Through Data to Action (EfC:PACE D2A). The content in this report is provided by the authors and does not necessarily represent the official position of or endorsement by the Centers for Disease Control and Prevention
The Nevada State Undergraduate Research Journal - Volume 10 Issue 2
No full textThe Nevada State Undergraduate Research Journal (NSURJ) was established in 2011 by the Associated Students of the University of Nevada (ASUN). In the Fall of 2014, NSURJ published its first volume. Now, NSURJ celebrates its eleventh year of publishing original, thesis-driven, professionally reviewed undergraduate research. NSURJ was founded to empower the undergraduate student body of Nevada and provide an outlet for their original, creative, and scholarly work. In 2024, these researchers travelled to Sri Lanka under a National Science Foundation Grant received by the Honor's College. Students and faculty travelled to Wasgamuwa National Park to participate in a variety of programs aiming to mitigate human-elephant conflicts, where they went above, beyond, and abroad normative research.NSF Grant #2107351, IRES Track I: Modeling Human-Elephant-Conflict Using GIS Methodologies with Engaged Community Ecosystem Management near Wasgamuwa National Park, Sri Lanka, Board of Regents, NSHE, obo University of Nevada, Ren
Isolation and Quantification of a Three-Component GPS-Signal Anomaly in the Western United States Occurring Between 2001 & 2005: A Geodetic Perspective
No full textA subtle, yet significant, anomalous signal is observed in the three components (east, north, up) of residual GPS station time-series across the western United States between the years 2001 and 2005. This anomaly is most prominent in the vertical and east components, with maximum amplitude occurring around mid-2003 roughly centered around Utah where a peak amplitude of 5-7 mm in the vertical component is measured. Localized variations are also observed in the Pacific Northwest. Here, we aim to isolate, quantify, and confirm the existence of this anomalous signal in the United States. We analyze a 10-year dataset (2000-2010) of daily solutions from 358 unique GPS stations across the United States and Canada. The signal persists after a robust time-series analysis is performed. The analysis removes long-term velocity trends, annual and semi-annual signals, and non-periodic surface loads of non-tidal atmospheric and oceanic loading (NTAOL). This time span is chosen to encapsulate and highlight the proposed anomalous period observed between 2002 and 2005. Data from before 2001 and after 2005 serve as a baseline for statistical comparison. A 365-day windowed average and median for each GPS station are computed and binned into various spatial extents, which are then plotted and mapped for regional analysis. Our analysis and subsequent results provide strong statistical evidence for the existence of a prominent anomaly across the United States between 2002 and 2005. Our comprehensive review of potential physical origins successfully explains and excludes various causes that include unaccounted hydrological loading/unloading and a mechanistic origin from a megathrust detachment under Nevada. While the precise underlying cause remains outside the scope of this study, leading theories include variations in the length of day (LOD) and deep Earth geophysics for which the hypothesized foundation originates from the interactions and dynamics at the core-mantle boundary
AIEI Webinar Series on Balanced Mix Design (Session 4 of 5): Testing Conditions
No full textThis webinar focuses on two key considerations for Balanced Mix Design (BMD) testing: mixture aging and testing temperature. Both parameters can be adjusted by agencies to better reflect local environmental conditions and material characteristics. The discussion covers the importance of aging in evaluating cracking performance, various aging methods, and how testing temperature influences rutting evaluations.United States Department of TransportationFederal Highway Administratio
Assessing the effects of deficit irrigation on alfalfa grown in Northern Nevada
No full textIncreasing water demands and prolonged periods of drought are forcing many farmers in Nevada to grow alfalfa without meeting its full irrigation demands, a practice known as deficit irrigation. Deficit irrigation (DI) is a strategy that can help increase crop water productivity (CWP), but it can also lead to water stress conditions that negatively impact alfalfa hay yield and may influence hay quality. This research is focused on alfalfa due to its importance for Nevada in terms of its economic benefits, widespread cultivation in the state, and its relatively high consumptive water use in comparison to the water demands of other crops, such as sorghum or corn. The main objective of this research was to assess the effects of practicing DI on alfalfa grown in northern Nevada. The main agronomic indicators that were considered to analyze such effects were alfalfa dry yield, CWP, and nutritive value of two alfalfa varieties that were expected to have contrasting water demands, as one is marketed as drought-tolerant and the other as highly productive. Additionally, the relationship between leaf area index (LAI) and canopy cover (CC) was determined due to their importance as indicators of biophysical processes of plant canopies and their correlation with yield. Finally, root biomass and diameter were estimated using ground-penetrating radar (GPR) to assess the effects of DI on root development, as roots play an essential role in water acquisition and the storage of carbohydrates