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Reconstructing Ice Cap Changes in Northern Greenland Using Proglacial Lake Sediments
No full textThe Arctic is experiencing climate change induced warming at a rate 3 to 4 times faster than the rest of the globe due to a phenomenon known as Arctic amplification. To better understand the current effects of climate change and the paleoclimate of the Arctic, we turned to a proglacial lake in Northern Greenland. Peary Land, a polar desert, is the northernmost region in Greenland and is characterized by a barren landscape. Our study site, Lake Southwest (LSW), is surrounded by small, cold-based glaciers which drain directly into the lake. LSW is a small proglacial lake and provides us with a high-resolution sediment archive that is strongly impacted by glacier dynamics. Lake sediments here capture minute climatic fluctuations over the last ~3,500 years (basal age = 1700 BCE) as retreat and growth of the glacier(s) directly provides sediment into the LSW basin via bedrock erosion. Grain size analysis, 210Pb & 137Cs isotope analysis, and x-ray fluorescence scanning were completed on the 1.5-meter-long core recovered from LSW in 2021. We found that meltwater from the nearby ice caps/glaciers to be the largest contributing factor of non-organic material into LSW. The length of ice-free vs. ice-covered conditions limited the amount and size of sediment which could have been transported into the lake, with said conditions a reflection of a rapidly changing environment. We saw coarser-grained sediments only starting to appear in greater relative abundance over the last 100 years. Changes in the isotope data (specifically Ti and Ca) throughout the core appear to take longer to respond to these fluctuating conditions, whereas grain size changes relatively fast. Further research into a potential relationship between diatom abundance and grain size changes over the last centennial is required to determine if this is an isolated event within the LSW catchment area or applicable to the entire region of Northeast Greenland.Geolog
Leveraging Technology To Support The Goals Of Dual Language Bilingual Education: An Explanatory Sequential Mixed Methods Study
No full textThis explanatory sequential mixed methods study explored how and why dual language (DL) teachers used technology and the extent to which their use of technology supported the goals of DL of bilingualism, biliteracy, academic achievement, and sociocultural competence. The study was guided by Mishra and Koehler’s (2006) technological pedagogical content framework, Bunch’s (2013) pedagogical language knowledge, Biesta’s et al. (2015) teacher agency framework, and Moersch’s (1997) levels of technology implementation framework. In the quantitative phase, data was collected with an original survey, and in the qualitative phase, data was generated through observations, interviews, and artifacts. Survey responses were analyzed using descriptive statistics. The qualitative data was analyzed using descriptive and in vivo coding. Codes were used to develop emergent themes. Overall, the DL teachers leveraged technology in various ways for planning, instruction, and assessment supporting their students’ academic achievement by building background knowledge, introducing concepts with comprehensible input, and providing vocabulary practice. They also used different digital tools to develop students’ sociocultural competence by building a strong classroom community, incorporating students into the curriculum, and teaching about different cultures. Moreover, the participants used technology to communicate with parents and seek professional development opportunities. DL teachers’ technology use was influenced by contributing and inhibiting contextual factors. Practical implications stipulated include providing DL teachers with appropriate planning time, supporting teachers with professional development that is relevant to DL and encouraging effective technology integration, allowing for curriculum flexibility, and investing in resources in the partner language.EducationDoctor of Philosophy (Ph.D.
The Superpower of Sleep: Poor Sleep Quality Predicts Worse Executive Control Under Conditions of Stress
No full textBackground: Over 60% of college students do not obtain the minimum recommended amount of sleep daily and over 54% experience above average levels of stress. Exposure to stress and poor sleep are each related to executive control, which is a set of cognitive abilities that are essential for daily functioning. Despite the prevalence of poor sleep and high stress, studies have rarely examined the joint impact of sleep and stress on executive control in students. Objective: The purpose of this study was to examine whether the impairing effect of stress on executive control is stronger in individuals who obtain poor sleep. Method: 76 undergraduate students recruited from William & Mary were randomly assigned to complete either a stress induction or a control task. Executive control was measured after the stress induction and control task. Self-reported sleep and actigraphy were tracked for a week prior to laboratory tasks. Results: Sleep quality on the previous night did not predict executive control measured under control or stress conditions. Whereas average sleep quality did not predict executive control measured under control conditions, poor average sleep quality predicted worse executive control under conditions of stress. Conclusion: Sleep quality impacts the extent to which executive control is impaired by stress. Due to the importance of executive control and the common experience of poor sleep and stress, specific interventions should focus on supporting students in obtaining sufficient sleep. Keywords: Executive control, stress, sleep quality, collegePsychologyBachelors of Science (BS
The Roles of Tidal Marshes in the Estuarine Biochemical Processes: A Numerical Modeling Study
No full textObservations suggest that the existence of tidal marsh can alter the oxygen and nutrient dynamics in adjacent water bodies, but assessing the impacts of large tidal marshes on an estuary is challenging. In this study, we use a modeling approach to investigate the roles of tidal marshes on the estuarine biochemical processes. The marsh model, which simulates the ecological functions of marshes at seasonal and annual time-scales, is embedded inside an unstructured-grid three-dimensional hydrodynamic and eutrophication model (SCHISM-ICM). This modeling system simulates the growth and metabolism of the tidal marshes and links biological processes to nutrient dynamics in the water column and sediment. This model dynamically simulates nutrient recycling and physical transport of the materials between marshes and open water through wetting-drying processes. This coupled model system is validated and successfully applied to the York River Estuary. Model results suggest that tidal marshes influence the local diurnal dissolved oxygen (DO) cycle by exporting dissolved organic carbon and high sediment oxygen demand in the marsh system through the tidal exchange. The high deposition rates of organics and diurnal DO cycle enhance the sediment release of phosphorus. On the other hand, marshes tend to decrease dissolved inorganic nitrogen in the water column by settling particulate nutrients and enhancing the denitrification process. The study demonstrates that tidal marshes exert substantial impacts on the estuarine biochemical processes. The developed tidal marsh model enhances eutrophication modeling and advances the understanding of the feedback effects between marsh biogeochemistry and estuarine eutrophication processes on a systemic scale.Virginia Institute of Marine Scienc
The Teshuvah of Jacques Derrida: Judaism Hors-texte
No full text‘Sparks’of Judeity appear everywhere within Derrida’s discourse. They illuminate previous gnomic terminology and propel future focus. His early deconstruction of Husserl’s pseudo-intuitive epoché in 1964, for example, accrues added significance when seen as a pseudo-interiority in The Gift of Death in contrast to the silent avowal of Kierkegaard’s Abraham in the moment of the Akedah. Levinas’s “ethics beyond ethics” allows Derrida to launch a second sailing after deconstruction. In the autobiographical “Circumfession,” Derrida assumes an inner life hors-texte and, sans exemplarity, a personal election as a Jew. In “Abraham, the Other,” he claims a “hyper-ethical, hyper-political, hyper-philosophical responsibility…that burns at the most irredentist core of what calls itself ‘jew.’” Derrida’s teshuvah finds its full fruition in later political writings such as “Force of Law,” enacting a new equation: “deconstruction is justice” (243)
Identity Building in Appalachia
No full textExpanding our understanding of how speakers with multiple conflicting identities may navigate the tensions between them through language use, this research looks at how two lesbians in Appalachia use the Appalachian feature of monophthongal /aɪ/ to express their identities as queer and/or Appalachian. Due to the studied and expressed disconnect between the two identities, I look at the possibility that the speakers will change their use of the Appalachian feature when discussing queer subjects. Using data from interviews conducted with the two speakers, I isolated two sections of speech pertaining to either queer or Appalachian topics and analyzed them for the amount of monophthongal /aɪ/ used in each section. Both speakers were found to use equal amounts of monophthongal /aɪ/ across both topics. This routine use of /aɪ/ is discussed using sociolinguistic and sociophonetic theories, such as Bucholtz and Hall’s (2004) concept of adequation and Reed’s (2014) proposed measure of rootedness.LinguisticsBachelors of Arts (BA
From The Hubbard Model To Coulomb Interactions: Quantum Monte Carlo Computations In Strongly Correlated Systems
No full textThe study of interacting quantum many-body systems poses one of the main challenges in areas including condensed matter physics, nuclear physics, cold atoms physics, quantum chemistry, and materials science. Currently, no general approach is capable of handling the full complexity of interacting quantum systems, providing systematically accurate results across different ranges of many-body models and materials. The continued development of more general and more accurate numerical methodologies is instrumental in meeting the challenges of understanding and predicting the properties of interacting quantum systems. Quantum Monte Carlo (QMC) methods represent an important class of many-body techniques extensively employed in studying correlated quantum systems. However, their effective application to non-trivial quantum systems requires specialized adaptations to ensure sufficient sampling efficiency. In this thesis, we introduce novel advancements and applications of the auxiliary-field quantum Monte Carlo (AFQMC) methods on Hubbard Model, atoms/molecules, and magic-angle twisted bilayer graphene. One of our development is the construction of pseudo-BCS wave functions using the one-body density matrix, offering a systematically improvable ansatz for correlated fermion systems. In AFQMC calculations, these pseudo-BCS wave functions serve as trial wave functions to control the sign/phase problem, using the two-dimensional Hubbard model as an example. Furthermore, we propose an interface between branching random walks and Markov chain Monte Carlo sampling, enabling seamless switching between these two. In the context of AFQMC, this interface facilitates a smooth transition from constrained-path sampling to constraint release, reducing systematic errors. We demonstrate this method in atoms and molecules, where improvements in accuracy can be clearly quantified and near-exact results are obtained. Leveraging the above developments, we apply AFQMC to investigate magic-angle twisted bilayer graphene (TBG) by studying a many-body Hamiltonian which consists of Bistritzer and MacDonald's single-particle model and realistic electron-electron Coulomb interactions. As our state-of-art AFQMC approach allows accurate treatment of the many-body Hamiltonian while controlling the sign problem, we determine the ground-state properties of this model across different integer fillings and quantify the errors from mean-field theory calculations. Overall, our developments in AFQMC offer broad applicability ranging from the Hubbard Model to Coulomb interactions which pave the way for intense studies encompassing abstract models, correlated materials with direct experimental comparisons, and what is in between involving both model and realistic interactions.PhysicsDoctor of Philosophy (Ph.D.
