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Resolving the Role of Wave-Induced Pressure Gradients on the Movement of Sediments in Nearshore Environments
No full textCharacterizing the hydrodynamic forces responsible for the initiation of sediment motion is fundamental for improved understanding of large-scale sediment transport processes in nearshore environments. Traditional sediment transport models assume incipient sediment motion is only driven by the force applied by bed stress (Bagnold, 1966; Shields, 1936) while more recent work has shown that incipient motion is influenced by the forcing of the horizontal pressure gradient due to surface gravity waves (Foster et al., 2006; Frank et al., 2015; Sleath, 1999). Wave-induced vertical pressure gradients can also destabilize the sediment bed through the process of momentary liquefaction (Florence et al., 2022b; Mory et al., 2007; Zen and Yamazaki, 1991). Understanding the rapid mobilizations of sediment beds requires improved resolution of the full wave-induced pressure field (i.e., the pressure in both the vertical and horizontal directions).
This dissertation seeks to advance our general understanding of how sediment moves in nearshore environments through several field experiments and observational methods. Observations of vertical pressure gradients are collected in the surf zone of an ocean beach using novel autonomous pressure-profiling instruments. These pressure-profiling instruments, known as Pressure Sticks, are designed and constructed as an integral part of this dissertation. Multiple Pressure Sticks deployed in a cross-shore array are used to directly measure the wave-induced horizontal pressure gradient. Pressure propagation into sediment beds is also investigated with these field observations. Continuous measurements of the location of the sediment-water interface are collected using an optical backscatter instrument called the SediMeter from Lindorm, Inc. These elevation observations are used to track the location of the pressure sensors relative to the sediment-water interface. Additionally, these elevation measurements are able to quantify any occurrence of small-scale net sediment movement.
Observations of vertical pressure gradients show that exceedances of momentary liquefaction thresholds occur within 16 - 20 cm of the sediment-water interface in the surf zone of a moderately-sloping, nearly macro-tidal sandy beach in New Hampshire. These exceedances occur at the onset of the wave crest. As the depth normalized wave height (H/h) and the Sleath parameter increase (specifically H/h \u3e 0.4 and Sleath \u3e 0.1) so does the likelihood of exceedances of momentary liquefaction thresholds. Additionally, the individual wave steepness and nonlinearity are other wave properties that may be necessary to induce large vertical pressure gradients.
Attenuation and phase lags of the pressure signal propagating into the sediment bed are observed. A numerical model for pressure propagation into sediment beds based in Biot Consolidation theory compares fairly well to the field observations of pressure propagation, with a percent difference of less than 6% and root mean square error values of less than 0.03 meters. Deviations between the model and the observations occur at sediment depths that are consistent with the depth and timing of large vertical pressure gradients that deviate from the expected hydrostatic condition. Additionally, model agreement decreased with decreasing water depths (increasing H/h). The sediment elevation measurements show that as the water depth increases with the rising tide, the sediment elevation decreases (losing sediment) while on the falling tide when the water depth is decreasing the sediment elevation increases (gaining sediment). During the high water depth times (lower H/h), there is minimal sediment movement. Exceedances of both the momentary liquefaction thresholds and the horizontal forcing thresholds occur during these times of sediment elevation change
INVESTIGATING THE ROLE OF SOUNDSCAPE PROPERTIES AND GENETIC MATERIAL AS SENTINEL INDICATORS OF THE ACOUSTIC ENVIRONMENT IN GULF OF MAINE COASTAL MARINE ECOSYSTEMS
No full textABSTRACT By identifying soundscape properties and taxa detected with metabarcoding that accurately predict substrate composition, assumptions about propagative properties of the environment can be rapidly formed without the use of active acoustic sensing or invasive environmental sampling techniques. “Sentinel indicators,” are variables, processes, or components within ecosystems that can be measured or quantified and have sensitivity to environmental pressures. Passive acoustic monitoring (PAM) and metabarcoding of seawater samples (MSS) are two minimally invasive potential methods of identifying sentinel indicators of soundscape and propagation properties of marine habitats by detecting the presence of marine taxa and extracting information from soundscapes. To better understand how soundscape features are related to environmental components that impact sound propagation, an observational experiment was conducted comparing the soundscapes of three different habitat types in coastal Gulf of Maine (GoM) waters: eelgrass, macroalgae, and sand. Using the Soundscape Code (Wilford et al., 2021) to rapidly and quantitatively characterize soundscapes of different habitats revealed soundscape properties are indicators capable of discriminating among coastal habitats at fine spatial scales using discriminant analysis. Impulsiveness and Uniformity metrics are important sentinel indicators for predicting habitat composition from acoustic recordings, demonstrating the value of quantifying soundscape properties beyond amplitude. This ability to efficiently obtain information about the acoustic environment is valuable for informing propagation models associated with marine biota as well as for quantifying uncertainty in the use of acoustic sensing instruments by humans such as echosounders. Both PAM and MSS are viable, minimally invasive methods for long-term detection of marine biota. A comparative study of these observational techniques was conducted to determine whether taxonomic detections from MSS could be predicted by Soundscape Code metrics (SCMs), and to identify which method serves as a more reliable detector of sound producing taxa. The present investigation revealed that there was little overlap in sound producing taxa detected by either method. Snapping shrimp were the dominant biological sound source in acoustic recordings across all habitats and locales, but were not detected with MSS. Fish were the second most prevalent source of biological sound, though these detections were not identified to species level in the acoustic recordings. Using MSS, 28 taxonomic groups of fish were detected with the MiFish-U primer set, many of which include sound producing species. Phocidae was the only family of marine mammal detected in metagenomic samples, while there were no confirmed detections of marine mammals in acoustic data that could be positively taxonomically identified. Vessel traffic and construction were dominant, high amplitude anthropogenic sound sources in nearly every habitat due to the close proximity of recorders to areas with high anthropogenic activity. These high levels of anthropogenic sound likely masked many biological sound sources and may have also influenced the behavior of sound producing taxa in a way that further reduced their detectability. Overall, MSS proved the stronger identifier of sound producing taxa, though this was a product of the broad taxonomic scope of taxa detectable with metabarcoding and was not a reliable indicator of which taxa make the greatest contribution to soundscapes. To determine whether Soundscape Code metrics were able to serve as reliable predictors of the taxonomic profiles of GoM habitats, partial least squares discriminant analysis (PLS-DA) models were developed at the Order and Family levels. The model that explained the greatest amount of variance in taxonomic profiles used 35 Orders that were identified as indicators of geographic locales using Indicator Species Analysis (ISA). However, of the four best performing models, none possessed any predictive power, demonstrating that Soundscape Code metrics did not serve as reliable predictors of taxonomic profiles for the sampled habitats. The likely explanation is that the soundscapes recorded were dominated by anthropogenic and geophysical inputs, as well as snapping shrimp, all of which were absent in the taxonomic profiles detected with MSS. Reliable predictive models still may be possible for soundscapes dominated by biological sound sources, but for the habitats investigated, a strong relationship did not exist between acoustic predictors and genetically detected biological responses
Age Distribution of Minors Portrayed in Image-Based Sexual Abuse and Child Sexual Abuse Material
No full textChild sexual abuse material (CSAM) poses a significant threat, especially in the current technological age. A better understanding of victim characteristics is needed to direct investigation and prevention efforts properly. However, determining the age distribution of children in CSAM has been difficult due to numerous factors, including differing laws governing CSAM, the priority placed on investigating younger victims, and the difficulty of determining from images alone the age of young people. This meta-analysis sought to understand the proportion of image abuse victims who are under the age of 13 compared to those who are 13 years or older and whether this proportion differed by data source or year of CSAM collection. It found that the overall prevalence of victims under the age of 13 as a proportion of all CSAM victims was 63%. This proportion differed by data source, particularly when examining data gathered from general population surveys. The prevalence of victims under the age of 13 as a proportion of all CSAM victims was 34%, while law enforcement (62%), internet watch agencies (74%), and web crawlers (87%) reported proportions greater than 60%. This meta-analysis also noted a significant increase in adolescent victims since 2020, most likely due to both the increase in general population surveys, which allowed older victims an avenue to report their experiences without fear of negative reactions, and changing technology and social norms that have increased the production of youth-produced sexual images. The findings of this study suggest that there are more victims aged 13 or older than are represented in law enforcement and agency studies due to the priorities such organizations place on investigating images of pre-pubescent victims. While this bias may have good justifications, the estimates of age distribution in CSAM that include law enforcement and agency reports will misrepresent the true age distribution. Future research should investigate other methods for prioritizing CSAM cases, such as the severity of abuse depicted in the images or the recency of the report
Rhode Islanders Divided on Sinking of Boats Off Venezuelan Coast, Oppose Overthrowing Maduro 11/19/2025
No full textRhode Islanders are about evenly split on the recent sinking of suspected drug trafficking boats off the Venezuelan coast but clearly oppose attempting to remove Venezuelan President Nicholas Maduro from power. More than six in ten Rhode Island residents disapprove of President Trump\u27s handling of the economy, with those who disapprove of his economic choices most often citing tariffs and the prices of goods as the reasons why they feel that way. Nearly half of Rhode Islanders support the deal to end the recent federal shutdown but two-thirds of Democrats are opposed. A majority support extending Obamacare premium subsidies, a key Democratic demand during the shutdown, and nearly all believe federal workers who were furloughed or remained on the job during the shutdown should receive backpay
Essays on Economic Evaluations of Environmental Conservation
No full textThis dissertation advances the field of environmental economics by addressing critical gaps in the non-market valuation of habitat conservation and dam removal. Three interrelated studies refine methodological approaches to stated preference valuation of habitat conservation and dam removal decisions and provide empirical insights that enhance our understanding of how individuals and communities value ecological restoration.
The first essay focuses on New England\u27s urgent need for conservation action due to habitat loss, driven by human activities like deforestation and urbanization. The study evaluates New England’s private homeowners\u27 investment decisions in wildlife-friendly landscaping by incorporating both time and money. This approach goes beyond traditional monetary valuation frameworks, acknowledging that conservation efforts require both financial contributions and personal engagement. Using a survey of over 2,000 homeowners in the region and a bivariate probit model, the study quantifies homeowners’ willingness to spend (WTS) time alongside their willingness to pay (WTP) money for wildlife habitat landscaping, offering a more comprehensive measure of homeowners\u27 commitment to local habitat restoration. Also, the study identifies factors that influence homeowners’ time and money investment decisions. Findings reveal that homeowners are willing to invest at least 101 hours and $401 yearly to landscape their property to benefit local wildlife. Urban homeowners are more inclined to invest in conservation efforts than rural homeowners, and elderly homeowners (within retirement age) are less likely to invest time and money than their younger counterparts. While conservation awareness and knowledge of wildlife species encourage conservation participation, fear of damage caused by wildlife discourages involvement. The findings provide valuable insights for policymakers and conservation organizations in designing targeted policies and incentive programs that promote private land conservation in New England. The study’s contributions enrich the literature on private land conservation by demonstrating that time constraints and ecological awareness significantly influence conservation behavior.
The second essay advances the discourse on dam removal and river restoration by conducting the first meta-analysis of stated preference studies on dam removal. Given the increasing recognition of the ecological and social benefits of dam decommissioning and the predominantly case-specific studies on dam removal, this study synthesizes 17 studies spanning 25 years to evaluate trends in willingness to pay (WTP) for dam removal. The study identifies broader trends in WTP and evaluates how methodological and socioeconomic factors influence valuation estimates. Employing the multilevel random effects (MLRE) model on a Box-Cox transformed data, as the preferred model, the study addresses key meta-analysis challenges, including heterogeneity, heteroskedasticity, and within-study dependence. The findings show that WTP estimates decrease with a short payment duration (one year), the contingent valuation method compared to choice experiments, and factors such as respondents\u27 income and age. Conversely, WTP estimates increase with larger sample sizes, the study country, and among male respondents. This meta-analysis provides a crucial basis for researchers and policymakers looking to generalize WTP estimates across various contexts.
The final essay examines the economic implications of dam removal, using primary data from a referendum-style contingent valuation survey on the Mill Pond Dam in Durham, New Hampshire. The study focuses on the Kaldor-Hicks (K-H) criterion of social welfare to examine the economic plausibility of a policy referendum. This study is among the first to apply the K-H criterion to evaluate dam removal policies, assessing whether majority-supported referendum outcomes truly lead to socially efficient decisions. The study makes a methodological and policy contribution by disaggregating stakeholders into supporters and opposers of dam removal and incorporating willingness to accept (WTA) compensation for those opposing removal. Unlike most valuation studies that focus solely on WTP for ecological improvements, this research captures the full spectrum of economic preferences by recognizing that environmental policies create both winners and losers.
The study estimates mean WTP among supporters and mean WTA among opponents of dam removal, revealing the extent of compensation required to make removal a Pareto-improving decision. Using the aggregate WTP and aggregate WTA as proxies for social benefits and losses, the findings show net societal benefit based on the K-H criterion. However, the uncertainty in the valuations (with WTA confidence interval spanning zero) implies that it is difficult to make firm conclusions on welfare and the plausibility of the policy to remove the dam. The key contribution of this study is in pioneering the K-H criterion to reveal welfare trade-offs obscured by referendum vote shares, offering a novel economic lens for environmental policy.
In conclusion, these studies offer a comprehensive evaluation of the non-market values associated with habitat conservation and dam removal. The dissertation’s contributions lie in its inclusion of time in private conservation decisions, the incorporation of the Kaldor-Hicks criterion of social welfare in referendum-based policy evaluation, and the first meta-analysis of WTP for dam removal, highlighting important factors that influence stated preference valuation of environmental conservation
ENVIRONMENTAL DRIVERS OF PHYTOESTROGENS IN FORAGE LEGUMES
No full textForage legumes are an important source of feed in animal agriculture. However, some legumes produce phytoestrogens, a group of secondary compounds that mimic the animal sex hormone estrogen. Livestock that consume phytoestrogen-rich forage legumes may experience reproductive problems and can serve as a source of phytoestrogens entering the human food supply through milk. Phytoestrogens in legumes are thought to be involved in mediating plant responses to environmental stress and act as signaling molecules to establish symbiotic relationships with microbes, yet there is little data on how environmental cues or management factors influence phytoestrogen concentrations in forage legumes. This research aimed to fill that gap for multiple forage legume species through a semi-systematic literature review, a field experiment representing a range of harvest practices, and several controlled environment experiments manipulating different environmental cues known to vary in the field. In the semi-systematic literature review, we found that phytoestrogen concentrations can vary widely (from 0.1 to 37.8 mg/g of DM) among different forage legume species and cultivars. Further, phytoestrogen concentrations in the milk of dairy cows can vary from 50.8 to 1,658.9 μg/L, depending on the legume species and proportion of legumes in the feed ration, with equol making up most of the phytoestrogen compounds detected. Adverse reproductive health effects of phytoestrogens on cows include impaired fertility, decreased corpus luteum function, lower conception rates, and increased silent heat. In greenhouse and field experiments, we found that red clover has much higher baseline phytoestrogen levels than white clover, while concentrations in kura clover and cowpea were very low or nondetectable. Among the harvest management practices we investigated, harvest frequency (three versus five cuts per growing season) had the greatest influence on phytoestrogen levels in both red clover and white clover. In the five-cut treatment, phytoestrogens varied widely between cutting events, while in the three-cut treatment, concentrations remained relatively stable across cuts. Individual phytoestrogen compounds showed similar patterns of variability based on harvest frequency. In a greenhouse study where plants were subjected to moisture stress, drought stress increased total phytoestrogen concentration in red clover by 100%. Waterlogging stress did not increase total phytoestrogen concentrations. Among the plant physiological responses measured in red clover, leaf water potential was the best single predictor of variation in formononetin, biochanin A, and total phytoestrogen levels. Phytoestrogen concentrations in kura clover were low or undetectable, regardless of water stress treatment. Two greenhouse experiments were conducted to examine the influence of insect herbivory on phytoestrogen concentrations in red clover, kura clover, and white clover. In experiment I, herbivory over a seven-day period increased phytoestrogen levels in red clover by 112% but not in kura clover. In experiment II, herbivory over a nine-day period followed by a nine-day recovery period, resulted in total phytoestrogen levels in red clover that were 84% higher compared to the control, while only glycitein concentration was increased when herbivory occurred for a full eighteen days. In a growth chamber study manipulating temperature and CO2 concentration, elevated temperature decreased total phytoestrogen concentration in red clover by 50% compared to the ambient control. While elevated CO2 altered the concentration of daidzein in red clover, it did not influence total phytoestrogen concentration. The phytoestrogen concentration in cowpea was below detection level regardless of temperature or CO2 treatment. Taken together, these results suggest that, among forage legumes commonly grown in the Northeast US, red clover is by far the most phytoestrogenic, and that a variety of biotic and abiotic factors can strongly influence its phytoestrogen concentrations
Design and Development of Systems for Wave-Soil-Structure Interaction Modelling in a Geotechnical Centrifuge
No full textAs hurricanes, and therefore storm surges, become stronger on average, civil engineering research has increasingly focused on the impact of flooding on coastal communities. While hurricane-induced flood scour has been understood to be a mechanism of structural failure for decades, there is still not a complete model for scour in the near-coast environment. To build on the current body of scour research, an apparatus for the physical modelling of wave-soil-structure interactions has been developed for the University of New Hampshire geotechnical centrifuge laboratory. The new model container design is capable of wave generation, wave absorption, and the real-time measurement of pore pressure development in soil and structural rocking as a result of wave action. This combination of experimental capabilities is relatively unique among contemporaneous research, especially in the geo-centrifuge. Calibration experiments performed using the container verified that wave generation and absorption were reasonably accurate to expected values. Additional preliminary experiments demonstrated the container’s capability to measure the impact of a structure’s presence on wave-soil interactions. Furthermore, the system is futureproofed for further investigation using the apparatus; live-test soil desaturation, lateral forcing on model structures, and tracking of scour development are all possible using the container as currently designed
DIFFERENTIATED LEARNING IN AN UPPER-LEVEL UNDERGRADUATE PHYSICS THEORY COURSE
No full text‘One-size-fits-all’ education aims to cater to the ‘average’ student, but the ‘average’ student does not exist. Students are individuals, each with a set of needs, abilities, preferences, and interests unique to them. A variety of instructional approaches should thus be used to differentiate students’ learning. This differentiation has been studied mostly for K-12. My study extends this research into an upper-level undergraduate physics theory course. For this phenomenographic pilot study, I interviewed ten students about the differentiated homework assignments in their upper-level undergraduate classical mechanics course at the University of New Hampshire. I performed an issue-focused analysis of the data, using the theoretical frameworks of physics identity and self-determination theory. This analysis shows that when given the choice of which homework questions to answer, some students intentionally and thoughtfully chose the questions that they believed would benefit their learning. Also, giving students this autonomy positively affected the students both in the course, beyond the course grade, and outside of the course in a variety of ways
Effects of silvicultural burns on Quercus rubra regeneration near its northern range limit
No full textNorthern red oak (Quercus rubra) is predicted to expand its range northward in the northeastern United States with climate change and could greatly improve resilience of managed forests by expanding the functional diversity. However, red oak regeneration across its range currently faces many challenges including predation, pathogens, and consequences of forest mesophication such as insufficient light and competition with more mesic species. The latter challenges are potentially caused by the near absence of fire in most northeastern forested landscapes since the early 1900s. Therefore, prescribed burns may help address these challenges and hence promote oak recruitment and establishment. We studied six prescribed burn/unburn pairs of stands from across the White Mountain National Forest in New Hampshire, USA, most of which were managed over the past decade, plus one unmanaged stand where a wildfire occurred. In summers 2023 and 2024, we surveyed naturally regenerated oak seedlings along transects representing gradients of burn intensity, distance from edge, overstory density, and soil disturbance. Seedlings were aged, measured for height and diameter at root collar, and assessed for herbivory and pathogen damage. We found seedling density to be almost three times greater in prescribed burn stands relative to paired unburned stands. Seedlings in burned stands also grew better, evidenced by greater diameter at root collar, greater extension growth, and more leaves. Our study demonstrates positive effects of prescribed burns in recently harvested stands for red oak regeneration near its northern range limit and affirms prescribed fire as a potentially beneficial silvicultural management tool in introducing the species north of its current distribution
Flexibly Changing Resource Allocation in Individuals with Mild Traumatic Brain Injury (mTBI)
No full textIntroduction: The current study examined how individuals with mild traumatic brain injuries (mTBIs) can shift their attentional efforts in real-time. These abilities were examined within a dual-task, during which individuals had to perform two tasks simultaneously. The first research question compared the performance of healthy controls and concussion participants on individual subtasks of the dual-task. The second research question explored how effective healthy controls versus concussion participants were in shifting their attentional resources. The final research question examined the effect of fatigue, specifically whether concussion participants would demonstrate a greater fatigue effect and have more difficulty at the end of the task.
Methods: 51 undergraduate and graduate students were recruited as participants for the current study. The healthy control group was comprised of 32 individuals. The concussion group was comprised of 19 individuals with self-reports of a head injury within one month and five years prior to the start of the study. Participants completed 2 different testing sessions. The first testing session was used to collect demographic information and complete cognitive assessments to characterize the sample. The experimental dual-task, composed of a letter identification task and a tracking task, was completed during the second testing session. Performance for each individual task was recorded (d’ (letter identification) and TTD (tracking)) and analyzed within separate generalized linear mixed models (GLMMs).
Results: Healthy controls and concussion participants did not significantly differ in performance on the letter identification task (d’). For the tracking task, healthy controls had significantly greater TTDs, indicative of worse tracking, compared to concussion participants. However, healthy controls demonstrated worse tracking during allocation policies that did not prioritize the tracking task, indicating appropriate shifting of attentional resources, compared to concussion participants who demonstrated comparable TTDs regardless of the allocation policy. Additionally, all participants demonstrated a fatigue effect for the tracking task, having worse tracking at the end of the task compared to the beginning.
Discussion: The results of the current study revealed that healthy controls are able to shift their attentional resources in real-time. Concussion participants did not demonstrate this ability, and as a result, a true attentional deficit within this group could not be identified. Additional analyses revealed that the control and experimental groups did not differ significantly on most demographic variables and experimental measures (i.e. NIH Toolbox), suggesting that more robust findings were not identified because the groups were too similar. Future research should include individuals with more severe injuries and persisting deficits and seek opportunities to increase task difficulty