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The Coevolution of Topography and Runoff Generation in Humid Landscapes
No full textTopography is an important control on runoff generation, as slope and relief affect hydraulic gradients, and curvature affects the convergence or divergence of flow paths. Over long timescales, however, runoff also shapes topography through surface erosion. This coevolution suggests that there may be a close relationship between landscape hydrology and topography that could provide insights into both hydrological and geomorphic processes. However, we do not have a strong theoretical framework for how topography and runoff generation should be linked, nor have there been many studies to determine how these links are expressed in the field. Here I address these areas, focusing on humid climates where runoff is primarily generated through groundwater return flow and precipitation on saturated areas. First, I present a new coupled model of runoff generation and landscape evolution that incorporates fluvial erosion driven by runoff from a shallow aquifer, hillslope diffusion, and uplift. Then, I nondimensionalize the model under the condition of steady and uniform groundwater recharge, and provide a mathematical framework for understanding the link between hillslope length, geomorphic process rates, and subsurface hydrological properties. Next, I explore the hydrological function of coevolved landscapes in more detail, focusing particularly on the emergence of variable source area hydrology. For this aim, I extend the model and nondimensionalization to include evapotranspiration and a simple representation of the vadose zone. I show, among other things, that coevolution with subsurface hydrology can explain why steeper landscapes are likely to have smaller variably saturated areas than landscapes with more gentle topography, and link this difference to subsurface properties and climate. Lastly, I test some of the model predictions in the field by exploring the hydrologic and geomorphic differences between two small watersheds in the Piedmont physiographic province near Baltimore that have contrasting subsurface architecture. I show that the site with a thin permeable subsurface has larger variable source areas and shorter hillslopes than the site with a thick permeable subsurface, as predicted by the model. A full parameterization of the model for the two sites suggests that subsurface properties are necessary to explain these differences
PREPARING EDUCATORS TO INCORPORATE TRANSFERABLE SKILLS INTO TEACHING AND TRAINING
No full textTransferable skills, such as critical thinking, problem solving, communication, and collaboration, are some of the most in-demand skills in today’s workforce. Despite modern pedagogical approaches rooted in problem-based learning (PBL), a framework that lends itself to the acquisition of transferable skills, students in high school classrooms still demonstrate differing levels of transferable skills while completing the same course curriculum. Using Bronfenbrenner’s (1979) ecological systems framework, I conducted a needs assessment study to explore factors contributing to student acquisition of transferable skills, operating on the assumption that one of the most significant factors to such acquisition was the students’ teachers. The needs assessment found that Project Lead The Way (PLTW) master teachers (trainers) face multiple challenges when teaching transferable skills during training, including training time, training platform (virtual or in-person), and participant engagement. Bandura’s (1994) self-efficacy theory informed this study’s intervention, which assumed the form of a series of professional development workshops for PLTW master teachers. These professional development sessions engaged teachers in collaboration activities to promote their self-efficacy and provide them with resources they could use in their practice to assist in students’ development of transferable skills. More specifically, this mixed-methods intervention-based study aimed to help PLTW master teachers develop knowledge of the transferable skill resources available to them within the PLTW curriculum, increase their self-efficacy in teaching transferable skills, and increase their self-efficacy in their ability to engage others in collaboration during training. The study found that less than half of the participating master teachers were integrating transferable skills into their practice. The intervention resulted in a notable increase in the teachers’ self-efficacy regarding their ability to teach transferable skills. Focus groups and survey responses highlighted the need to increase master teachers’ awareness of PLTW’s transferable skill resources. Implications for future research are explored, including following up with this study’s participants to determine the long-term effectiveness of the professional development provided
THE MECHANISM AND FUNCTION OF EXTRACELLULAR VESICLE RELEASE BY GDE2 AND GDE3
No full textGDE2 and GDE3 (Glycerophosphodiester phosphodiesterase 2/3) are members of a small family of six-transmembrane proteins. These proteins have the catalytic ability to cleave GPI-APs (Glycosylphosphatidylinositol-anchored proteins) off the cell surface, which is linked to most of their known biological functions. During my thesis, I discovered a novel role for these enzymes in releasing extracellular vesicles (EVs). EVs are small lipid particles released by cells that are important for intercellular communication. Overexpression of GDE2 or GDE3 in HEK293T cells is sufficient to release EVs. Characterization of GDE3-EVs indicates that they are a subtype of EV released from the plasma membrane called Microvesicles (MVs). These GDE3-MVs contain AnnexinA1 and GDE3 itself. In astrocytes, where GDE3 is expressed, GDE3 releases MVs by remodeling the actin cytoskeleton via the protein WAVE3 (WASF3, Wiskott-Aldrich syndrome protein family member 3). Because EVs function as intercellular signaling platforms, I hypothesized that GDE3-derived EVs regulate neuronal function. In a series of experiments with Daniel Daudelin, we found that neurons of Gde3-KO (knock-out) mice have impaired post-synaptic function and that EVs produced by WT (wild-type) astrocytes can restore this post-synaptic deficit. Importantly, EVs produced by Gde3-KO astrocytes, or astrocytes with inhibited WAVE3 function, cannot restore post-synaptic function of Gde3-KO neurons. This reinforces the specificity of the GDE3-WAVE3 biogenesis pathway for producing functionally distinct EVs. The biology of GDE2-derived EVs remains less clear. Unlike with GDE3-EVs, the molecules that define GDE2-EVs and the biogenesis pathway of these EVs are unknown. GDE2 is expressed in neurons where it appears to play a role in the production of EVs following stimulation of neurons. To advance EV work on GDE2 and GDE3, I developed external epitope-tagged versions of both proteins, which allowed immunoprecipitation of EVs containing either protein. This allows for precise capture of GDE2/3+ EVs, which will assist in the unbiased characterization of them in vitro and in vivo. In my thesis, I advanced our understanding of the GDE enzymes by defining a new role in EV release. My work has also highlighted the diversity of EV types, biogenesis pathways, and functions
AIR POLLUTION, COMMUNITY MOBILITY, AND CLINIC-BASED COGNITIVE AND PHYSICAL FUNCTION IN OLDER ADULTS
No full textBackground: As the proportion of older adults in the population rises, identifying effective strategies to prevent or delay dementia onset is a public health priority. Evidence suggests that air pollution is a modifiable risk factor for dementia. Studies also show that constrained self-reported community mobility is associated with increased dementia risk. Yet, it remains unclear how novel measures of air pollution (i.e., toxic chemical releases) or objective community mobility are associated with older adults’ health outcomes. We examined associations between two potentially modifiable neighborhood-level factors – toxic chemical emissions (Aim 1) and community mobility (Aim 2) - and older adults’ cognitive or physical function. We also investigated whether acute (i.e., daily) air pollution exposure was associated with community mobility (Aim 3).
Methods: Data for Aim 1 came from the Cardiovascular Health Cognition Study. Logistic regression models examined associations between 5-year average (1988-1992) toxicity-weighted concentration emissions from industrial facilities and odds of prevalent dementia. Discrete-time proportional hazards models assessed dementia risk through 1999. Aims 2-3 leverage data from the Program to Improve Mobility in Aging (PRIMA) study. Spearman correlations characterized associations between clinic-based performance measures and GPS-derived community mobility (Aim 2). Mixed effects ordinal logistic regression models were used to examine associations between daily air pollution concentrations and community mobility (Aim 3).
Results: Living in census tracts with higher toxicity-weighted concentrations was associated with higher odds of prevalent dementia (OR=1.34; 95% CI: 1.01, 1.78) and a heightened vascular dementia risk (HR=1.65; 95% CI: 1.04, 2.61). From Aim 2, more out-of-home time and a larger activity space were associated with better performance on clinic-based measures of walking endurance and executive functioning. Results from Aim 3 suggest that short-term exposure to PM2.5 and NO2 was not significantly associated with daily community mobility.
Conclusions: Toxic chemical emissions and community mobility are two potentially modifiable neighborhood-level factors that should be considered in public health interventions and policies seeking to reduce dementia risk. These findings highlight the importance of considering features of the neighborhood environment when examining health outcomes and motivate the need for policy-level changes targeting risk factors that are difficult to implement at the individual-level
The Dismal Ledger: Encounters Between Parliamentary Procedure, Dysfunction, and Formulation of the Federal Budget
No full textThis thesis surveys parliamentary dysfunction in the United States Senate within the curation of the federal budget. Often, research surrounding the federal budget comes in quantitative methods, seeking measurable impacts on fiscal policy. Quantitative methods are used within this work to explore the role procedural interpretation, political
economy, and intergovernmental lobbying has on parliamentary procedure in the United States Senate.
This thesis finds that procedural misinterpretation, political economy, and
intergovernmental lobbying does have an impact on the role the federal budget plays in parliamentary procedure in the Senate.
The federal budget reaches into nearly every aspect of American government,
acting as a critical vehicle of the social contract. As such, the federal budget can act as a carrier of influence, lobbying, and dysfunction into all branches of government and the federalist system
EXPLORING MUTAGENESIS AND DEVELOPING NOVEL NUCLEAR MAGNETIC RESONANCE TECHNIQUES TO STUDY NONRIBOSOMAL PEPTIDE SYNTHETASE CARRIER PROTEIN AND CYCLIZATION DOMAINS
No full textNonribosomal peptide synthetases (NRPSs) are a class of enzymes that produce complex natural products with applications in medicine and industry. Their modular architecture is targeted as a means to introduce new chemical groups into custom peptides for battling many global health threats such as antimicrobial-resistant pathogens and viruses. These mega-enzymes are highly dynamic and engage in transient interactions. Thus, bioengineering NRPSs is challenging as breakdowns in domain-domain and domain-substrate interactions can occur. Two key domains, condensation and carrier protein domains, interact resulting in the formation of bonds between amino acid substrates. How these domains engage each other amidst a complex multi-domain architecture is unknown.
To better understand the basic principles of condensation domain and carrier protein interactions, we turn to our model system yersiniabactin synthetase. Within this system, I characterized a specialized condensation domain, the cyclization domain Cy1, and its interactions with one of its partner carrier protein domains, ArCP. I performed mutagenesis on Cy1 to explore mechanistic questions involving engagement with ArCP and revealed that some point-site mutations globally remodel Cy1. These mutants exhibited impaired function, dynamics, and an allosteric response to the substrate-loaded form of ArCP. These results highlight the need to integrate domain dynamics and allostery into NRPS mechanisms and more generally emphasize the impacts of mutagenesis amidst a dynamic protein landscape.
To study NRPS proteins and their interactions in vitro requires both homogenous samples and the use of nuclear magnetic resonance (NMR) to reveal atomic-level details. I advanced upon previous works to generate substrate loaded carrier proteins using a modified one-pot chemoenzymatic route and apply NMR to monitor this biosynthetic process. Additionally, I developed new NMR methods to filter signals from isotopically labeled carrier proteins harboring unlabeled prosthetics and substrates. These new methods create a foundation for focusing on interactions of the phosphopantetheine arm and substrate without interferences from signals arising from the protein core. The new one-pot protocols and methods I have developed in this work will be useful for future studies exploring interactions between carrier proteins and their many partners in solution
The Reception of Marcus Iunius Brutus in Roman Imperial Literature: Roman Exemplarity and Collective Memory throughout the Ages
No full textOn March 15th 44 BC, Marcus Junius Brutus and his companions stormed the Capitoline Hill and they barricaded themselves within, after they assassinated the dictator, Julius Caesar. The aftermath of Caesar’s assassination reignited political chaos in Rome and renewed civil wars. In writing about this political turmoil, historians and literary writers over two millennia, from Cicero to Voltaire, attempted to give meaning to the actions of Brutus. This dissertation engages with the reception of Brutus in Roman imperial writers, Latin and Greek, and the significances which they impart to Brutus. Previous scholarly studies mined imperial authors to reconstruct the events of the Ides of March or to give a biographical account of Brutus’ life. A reception study of Brutus in imperial literature complements existing scholarship, by evaluating the methodology by which imperial authors interpret Brutus. In particular, we will survey how imperial authors cast Brutus as an exemplum – a paradigm for moral or immoral action, deemed imitable (or not) by posterity.
Chapter one examines Brutus as exemplum libertatis, in which Brutus signifies liberty, ranging from political freedom to Stoic conceptions of freedom. Chapter two considers Brutus as the “protector” of state institutions and traditions, whether of the res publica/mos maiorum (in Latin senses) or of democratia/isonomia (in Greek ones). Chapter three surveys Brutus presented as an ingrate for killing Caesar, the pater patriae (“father of the fatherland”), and thereby became a model of parricide. Chapter four analyzes the creation of Brutus as “conspirator”, a novel exemplum emerging only in the imperial age. Finally, chapter five surveys Brutus as a man of letters.
Although the exempla of Brutus crystallized around key events, details, and themes, the meanings and interpretations of them are as numerous as the texts which attempt to encapsulate and describe Brutus. Brutus and his exempla demonstrate how the collective memory of an individual persists and evolves over the centuries, not only in its malleability to fit new realities, but also by providing later ages a discursive framework by which they can engage with the past and their own social milieu
INTERNATIONAL RESEARCH COLLABORATION
Get PDFInternational collaborative research incorporates cross-country groups that allocate research affairs, manage research, and encourage research outcomes to develop comprehension and encourage affirmative alterations in execution. International research can benefit a specific field, incorporating more important influence and extensive pertinence. It also allows us to enlarge research discoveries to various cultures, districts, and communities. Also, international collaborative research offers opportunities to create reciprocally advantageous connections and decipher worldwide issues. However, with international collaboration, the challenges that come with it can also increase.
Utilizing responses from questionnaires and articles on international research
collaborations, this project aims to display the need for educational programs that can assist research administrators with overcoming barriers to international research collaborations. The responses from the questionnaires demonstrate that research administrators want educational opportunities to gain experience in how to deal with challenges that come from international research collaborations
On Mean Curvature Flows Coming out of Cones
No full textIn this thesis, we study several aspects of mean curvature flows (MCFs) coming out of cones. As geometric heat flows, MCFs are expected to immediately smooth out singular initial data, so it is natural to consider this phenomenon in the model case of cones. These flows also serve as models of possible continuations of MCFs after conical singularities. The topics discussed include the existence, uniqueness and symmetry of the evolution of cones.
In the first part, we study the existence and uniqueness properties of such flows. The most natural family are called self-expanders, which are extensively studied by Bernstein--Wang in a series of work starting from \cite{BWSpace}. Building on the theory of self-expanders, we first construct a family of non-self-similar MCFs coming out of a given cone, provided there is an unstable self-expander asymptotic to the cone. Using spectral analysis, we will then classify solutions coming out of a generic cone with low entropy.
In the second part, we show rigidity when we impose additional symmetry on the cone structure. In particular, we prove that for a rotationally symmetric double cone, any initially smooth MCF coming out of the cone remains rotationally symmetric at all future times, even past singularities. Note that the flows we consider are not only smooth self-expanders, but also the examples constructed in the first part. This generalizes earlier results of Fong--McGrath and Bernstein--Wang