Doctor of Philosophy

dissertationAdult second language (L2) learners often experience difficulty with novel L2 phonological contrasts, limiting their ability to establish contrastive lexical representations of L2 words. It has been demonstrated that the availability of orthographic input (OI), and variables interacting with OI, can shape the inferences learners make about L2 words' phonological forms. The present dissertation focuses on grapheme familiarity and congruence, in addition to L2 experience and the effect of instruction, in the case of native English speakers learning L2 Russian(-like) words presented in Cyrillic. Few studies have directly investigated effects of grapheme familiarity and congruence on phono-lexical acquisition simultaneously, systematically investigated the variables' effects on naïve and experienced L2 learners, or investigated how explicit intervention can mediate OI effects. The present dissertation addresses these gaps in our understanding. The two studies in this dissertation employed the artificial L2 lexicon paradigm. Taken together, the results indicate the following: (i) native language orthographic interference effects are robust in L2 word learning, especially when grapheme-phoneme correspondences are incongruent (unfamiliar and congruent stimuli did not cause difficulty); (ii) experience with the Russian language mediates this interference, with advanced learners performing near ceiling on all stimuli types and naïve learners performing least accurately; and (iii) naïve learners do not seem to benefit from textual enhancement and instruction prior to word learning in an experiment. The results of the present dissertation suggest that more research is needed to address the challenges associated with the interference effects of OI in L2 acquisition

Master of Arts

thesisRecent research indicates that knowledge of words' spellings can influence memory of phonological forms of second language (L2) words. For example, L2 learners whose first language uses the Roman alphabet remember newly-learned words more accurately when provided spelled forms in Roman orthography than when spelled forms are unavailable. Research also indicates that learners exposed to novel suprasegmental tone marks are more likely to remember tones associated with novel words and create tone-tone mark correspondences than learners not exposed to tone marks. However, while learners can use familiar letters and novel suprasegmental marks to make inferences about phonological forms, it is unknown whether learners can use entirely unfamiliar orthographic symbols. I therefore asked: Can learners use their knowledge of the alphabetic principle to infer phonological forms of new words when presented an unfamiliar L2 orthography? (Experiment 1). Did learners create graphemephoneme correspondences given orthographic representations? (Experiment 2). Native English speakers (no Arabic experience) were randomly assigned to Orthography or Control word learning groups. Six nonword minimal pairs contrasting Arabic velar-uvular contrasts (i.e., [k] and [q]) were randomly assigned picture "meanings". During a word learning phase, subjects saw pictures and spelled forms (either the word spelled in Arabic script-Orthography condition, or a meaningless sequence of Arabic letters-Control condition), and heard auditory forms. In Experiment 1, subjects determined whether a picture associated with, e.g., [kaʃu], matched an auditory form [qaʃu]. There was a significant effect of item type (p<.005), with matched items being easier, but no significant effect for subject group (p=.661) and no significant interaction of item type and subject group (p=.867). In Experiment 2, subjects determined whether orthographic representations and auditory words matched. Neither group performed significantly above chance on test items (Orthography mean = .513; Control mean = .539). Results suggest there are conditions under which novel scripts may not aid in learning L2 contrasts. However, it is unclear whether the lack of positive impact of orthographic representations results from difficulty associated with the Arabic script and/or perception of the target contrast

An Interdisciplinary Approach to Community-Engaged Research Surrounding Lead in Drinking Water in the Mississippi Delta

Childhood lead poisoning is a problem requiring interdisciplinary attention from toxicology, public health, social sciences, environmental law, and policy. In the U.S., Mississippi was ranked as one of the worst states for lead poisoning with limited childhood screening measures. We conducted community-engaged research by working with leaders in the largely rural Mississippi Delta region from 2016-2019 to collect household water samples and questionnaires and involve their communities in lead poisoning risk awareness and outreach. Drinking water from 213 homes was collected and analyzed for pH and lead concentrations. Highest lead concentrations were from households served by private wells, and detectable concentrations at or above 0.09 ppb were found in 66.2 percent of all samples. Nine samples exceeded 5 ppb, and these households received certified sink filters. Findings indicated that community-engaged research and outreach could be used to address data gaps relating to lead in drinking water in rural decentralized water systems

Altered Domain Structure of the Prion Protein Caused by Cu2+ Binding and Functionally Relevant Mutations: Analysis by Cross-Linking, MS/MS, and NMR

The cellular isoform of the prion protein (PrPC) serves as precursor to the infectious isoform (PrPSc), and as a cell-surface receptor, which binds misfolded protein oligomers as well as physiological ligands such as Cu2+ ions. PrPC consists of two domains: a flexible N-terminal domain and a structured C-terminal domain. Both the physiological and pathological functions of PrP depend on intramolecular interactions between these two domains, but the specific amino acid residues involved have proven challenging to define. Here, we employ a combination of chemical cross-linking, mass spectrometry, NMR, molecular dynamics simulations, and functional assays to identify residue-level contacts between the N- and C-terminal domains of PrPC. We also determine how these interdomain contacts are altered by binding of Cu2+ ions and by functionally relevant mutations. Our results provide a structural basis for interpreting both the normal and toxic activities of PrP

Characterizing RNA Dynamics at Atomic Resolution Using Solution-state NMR Spectroscopy

Many recently discovered non-coding RNAs do not fold into a single native conformation, but rather, sample many different conformations along their free energy landscape to carry out their biological function. Unprecedented insights into the RNA dynamic structure landscape are provided by solution-state NMR techniques that measure the structural, kinetic, and thermodynamic characteristics of motions spanning picosecond to second timescales at atomic resolution. From these studies a basic description of the RNA dynamic structure landscape is emerging, bringing new insights into how RNA structures change to carry out their function as well as applications in RNA-targeted drug discovery and RNA bioengineering

Exploring The Saturn System In The Thermal Infrared: The Composite Infrared Spectrometer

International audienceThe Composite Infrared Spectrometer (CIRS) is a remote-sensing Fourier Transform Spectrometer (FTS) on the Cassini orbiter that measures thermal radiation over two decades in wavenumber, from 10 to 1400 cm- 1 (1 mm to 7mu m), with a spectral resolution that can be set from 0.5 to 15.5 cm- 1. The far infrared portion of the spectrum (10 600 cm- 1) is measured with a polarizing interferometer having thermopile detectors with a common 4-mrad field of view (FOV). The middle infrared portion is measured with a traditional Michelson interferometer having two focal planes (600 1100 cm- 1, 1100 1400 cm- 1). Each focal plane is composed of a 1× 10 array of HgCdTe detectors, each detector having a 0.3-mrad FOV. CIRS observations will provide three-dimensional maps of temperature, gas composition, and aerosols/condensates of the atmospheres of Titan and Saturn with good vertical and horizontal resolution, from deep in their tropospheres to high in their mesospheres. CIRS's ability to observe atmospheres in the limb-viewing mode (in addition to nadir) offers the opportunity to provide accurate and highly resolved vertical profiles of these atmospheric variables. The ability to observe with high-spectral resolution should facilitate the identification of new constituents. CIRS will also map the thermal and compositional properties of the surfaces of Saturn's icy satellites. It will similarly map Saturn's rings, characterizing their dynamical and spatial structure and constraining theories of their formation and evolution. The combination of broad spectral range, programmable spectral resolution, the small detector fields of view, and an orbiting spacecraft platform will allow CIRS to observe the Saturnian system in the thermal infrared at a level of detail not previously achieved