UMD Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/3
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Item CROSS-LINGUISTIC DIFFERENCES IN THE LEARNING OF INFLECTIONAL MORPHOLOGY: EFFECTS OF TARGET LANGUAGE PARADIGM COMPLEXITY(2020) Solovyeva, Ekaterina; DeKeyser, Robert M.; Second Language Acquisition and Application; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Inflectional morphology poses significant difficulty to learners of foreign languages. Multiple approaches have attempted to explain it through one of two lenses. First, inflection has been viewed as one manifestation of syntactic knowledge; its learning has been related to the learning of syntactic structures. Second, the perceptual and semantic properties of the morphemes themselves have been invoked as a cause of difficulty. These groups of accounts presuppose different amounts of abstract knowledge and quite different learning mechanisms. On syntactic accounts, learners possess elaborate architectures of syntactic projections that they use to analyze linguistic input. They do not simply learn morphemes as discrete units in a list—instead, they learn the configurations of feature settings that these morphemes express. On general-cognitive accounts, learners do learn morphemes as units—each with non-zero difficulty and more or less independent of the others. The “more” there is to learn, the worse off the learner. This dissertation paves the way towards integrating the two types of accounts by testing them on cross-linguistic data. This study compares learning rates for languages whose inflectional systems vary in complexity (as reflected in the number of distinct inflectional endings)—German (lowest), Italian (high), and Czech (high, coupled with morpholexical variation). Written learner productions were examined for the accuracy of verbal inflection on dimensions ranging from morphosyntactic (uninflected forms, non-finite forms, use of finite instead of non-finite forms) to morpholexical (errors in root processes, application of wrong verb class templates, or wrong phonemic composition of the root or ending). Error frequencies were modeled using Poisson regression. Complexity affected accuracy differently in different domains of inflection production. Inflectional paradigm complexity was facilitative for learning to supply inflection, and learners of Italian and Czech were not disadvantaged compared to learners of German, despite their paradigms having more distinct elements. However, the complexity of verb class systems and the opacity of morphophonological alternations did result in disadvantages. Learners of Czech misapplied inflectional patterns associated with verb classes more than learners of German; they also failed to recall the correct segments associated with inflections, which resulted in more frequent use of inexistent forms.Item Effects of physico-chemical cues from the blood-brain barrier microenvironment on tumor cell migration and morphology(2019) Pranda, Marina Alexandrovna; Stroka, Kimberly M; Bioengineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Cancer metastasis is particularly deadly, leading to 90% of cancer deaths. During metastasis, tumor cells break off from a primary tumor and travel to distant sites. Metastasis to the brain results in a poor patient prognosis. However, several common cancers, such as breast cancer and melanoma, metastasize to the brain. In order to metastasize to the brain, tumor cells have been shown to cross the highly selective blood-brain barrier (BBB), which separates the brain parenchyma from the circulatory system. The BBB is highly impermeable, even for many chemotherapeutics, however, tumor cells are able to cross it by a poorly understood mechanism. The BBB consists of endothelial cells connected by tight junctions, and is supported by cells of the neurovascular unit, such as astrocytes. Furthermore, the composition of the extracellular matrix beyond the BBB is unique and contains hyaluronic acid (HA). In disease, HA organization or biophysical properties may become altered. The goal of this study was to investigate how specific physico-chemical interactions of tumor cells and the BBB microenvironment may impact tumor cell behavior at the BBB, as well as explore cold atmospheric plasma (CAP) as potential cancer treatment. This understanding could lead to better future therapeutics and a better prognosis for patients. We hypothesized that biophysical and biochemical cues from the BBB microenvironment, as well as the tumor cell phenotype, can influence tumor cells’ migration and morphology. In this dissertation, we investigated the interaction of tumor cells with astrocyte-secreted biochemical cues and the biophysical cues from a HA/gelatin extracellular matrix on tumor cell morphology, migration, and incorporation into an endothelium. Our results showed that tumor cell migration and morphology are significantly altered by astrocyte-secreted factors and the HA/gelatin extracellular matrix; however, the extracellular matrix is less significant during incorporation. We also showed that brain- and bone-seeking tumor cells display varied morphologies on matrices with niche-relevant mechanical properties. Finally, we demonstrated that CAP selectivity for reducing migration of tumor vs. normal cells is highly sensitive to cell culture media formulation. Together, these results provide new insights into tumor cell behavior at the BBB and inform future studies and therapeutic development.Item SYNTHESIS AND CONTROL OF MORPHOLOGY OF POLY METHYL METHACRYLATE AND POLY ACRYLIC ACID MICRO-PARTICLES BY THE MODIFIED SUSPENSION POLYMERIZATION TECHNIQUES(2015) Kim, Yunju Jung; Choi, Kyu Yong; Chemical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This thesis studied the synthesis and control of morphology of two kinds of polymers by modified suspension polymerization techniques. The first polymer, poly (methyl methacrylate), is a transparent thermoplastic polymer, which is typically used in diffusing film in the backlight unit of an LCD. Also, the synthesis of micron-sized polymer particles with complex internal morphologies such as hollows, multihollows, and multiporous structures is of growing interest in many technological applications such as microelectronic displays and microencapsulation. The direct synthesis of such materials is carried out in heterogeneous processes with controlled phase separation mechanisms. In such systems, detailed knowledge of heterogeneous polymerization kinetics and phase separation phenomena is essential for investigating the process characteristics. An in situ polymerization and phase separation technique has been used to construct a ternary phase diagram for the free radical precipitation polymerization of methyl methacrylate (MMA), n-hexane, and poly(methyl methacrylate) (PMMA) system. The onset of the phase separation point during polymerization is directly monitored in real time by laser light scattering (LLS) technique for a broad range of polymer concentrations. The presented method overcomes the difficulty of determining the cloud points by titrating unreactive blends of polymer and solvent at high initial monomer concentrations that lead to high polymer concentration and high viscosity of the mixture fluid at the system phase separation point. We present the micro dispersive suspension polymerization (MDSP) process to produce complex particle morphologies in a single-stage process. MDSP is a hybrid of suspension and dispersion polymerizations. The micron-sized polymer particles are polymerized by suspension polymerization, and the internal morphology of particle is polymerized by dispersion polymerization inside the polymer particles. Varying the initial conditions for the phase separation in precipitation and dispersion polymerizations, final particles’ morphology may change from solid polymer particles to complex porous polymeric structures. In this heterogeneous process, the system evolution depends on the composition and molecular characteristics of the coexisting phases and on the characteristics of the interface. Using MDSP, we were able to develop a phase diagram to show the regions of multi-hollow/porous and core-shell/pomegranate-like poly (methyl methacrylate) (PMMA) particles. We also show that controlling morphology of polymer particles by thermodynamic and kinetic variables is technically feasible. The second polymer, poly (acrylic acid), is an absorbing polymer. Superabsorbent polymers (SAP) can absorb and retain extremely large amounts of water or aqueous solutions relative to their own mass. Partially neutralized sodium polyacrylate is industrially a very important polymer for many applications. However, in industry sodium polyacrylate is mostly manufactured by bulk polymerization, and the resultant bulk polymer is pulverized using a kneader to obtain small discrete polymer particles. It is environment-unfriendly process and the produced granules from bulk have irregular shapes, rather than a spherical shape. This study is aimed at investigating the inverse suspension polymerization of acrylic acid to make spherical polymer particles. In particular, the study is focused on how the resulting polymer morphology and characteristics are affected by the polymerization conditions. A feasible and simple technique to obtain Na-polyacrylate microparticles with sizes below 10 µm was investigated using a high shear mixing device. To maintain the stability of submicron size of aqueous droplets in the oil medium, a co-surfactant system containing Span 80 and Tween 80 was used. Neutralization of acrylic acid was proved from EDX analysis. Na-polyacrylate submicron particles were characterized by size, surface morphology, swelling capacity, and conversion. When the speed of homogenization was lowered from 3000 rpm to 1000 rpm, particles over 10 µm were obtained, but more nano-sized particles were present outside. We also developed the technique above to increase polymer particle size to tens of microns. In this process, a wrinkled and cracked surface of Na-polyacrylate particles was observed in the special environment of post treatment. Surface area, swelling capacity, and swelling speed of different morphologies and sizes were characterized and analyzed. In order to synthesize spherical Na-polyacrylate particles with smooth surface regardless of post treatment, polymerization time was progressed longer than 20 hr. Na-polyacrylate particles had a solid structure at high conversion over 0.996 after longer than 15 hrs of polymerization, which made particles maintain their shapes regardless of post treatment. When a high monomer concentration was used in this polymerization, perfectly smooth and spherical polymer particles were obtained after 9 hr, which was faster than when a lower monomer concentration was used.Item Narrow Space : Designing the Interstitial(2015) Steen, Siobhan Marie; Rockcastle, Garth; Architecture; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This thesis is an investigation of the formal and phenomenological characteristics of a specific spatial morphology: narrow, tall, long, habitable space which occurs between at least two other spaces whether connected or not. This investigation does not aim to address all types of interstitial space. The general form of the space is the constant; variables include size, scale, modulation, intended and unintended uses. The method of investigation will be the creation of a matrix of examples that allows sorting by the various categories. It is expected that examining sorted categories will lead to a comprehensive and profound understanding of this spatial type. And that this, in turn, will prompt a program that will provide the basis for a demonstration of the range of uses of this spatial type. An investigation of the interstitial is intended to illuminate the author’s affinity and intuitive use of this spatial form in her work and to generate a framework for the author from which to approach architecture, using interstitial space intentionally as the primary organization and driver of form in future explorations.Item MORPHOLOGY IN URBANIZED STREAMS OF THE PUGET SOUND LOWLAND REGION(2004) Boyle, Pamela Roxana; Prestegaard, Karen; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Increased runoff from urbanization may result in erosion to the stream channel and banks, leading to channel incision, bed changes, loss of instream debris and habitat, and an overall reduction of heterogeneity and channel complexity. These impacts are especially evident in low gradient, gravel-bed, meandering streams - the major type of stream in the Puget Sound Lowland region. The failure of many stream restoration projects is due to a lack of understanding of how morphological features of a stream respond to hydrological changes. Single cross-section methods (instead of reach-level) are generally used and may not adequately portray the complexity, or variation, of the stream channel and bed. Three main hypotheses in this thesis are: 1) a single cross-section taken within a reach does not adequately describe a stream compared to a mean value calculated from several measurements; 2) urban streams with more urbanized drainage areas have higher shear stresses, and thus move larger bed particles and have higher reach mobility; and 3) urban channels have less channel complexity than non-urban channels. Results showed that a single cross-section may not adequately describe the morphological variables of a stream reach; however, this method may be appropriate for calculating reach shear stress. In addition, shear stress and mobility were not found to increase with increasing urbanization. Furthermore, complexity was not found to decrease with increasing urbanization. These two latter results indicate that urbanization (or percent imperviousness) alone cannot be used as a variable to investigate changes in stream morphology and hydraulics. In fact, a measure of sediment supply could be considered an additional independent variable by which to study urbanization impacts to streams. Substrate distributions from this thesis also support this finding.Item The Development of Syntactic Complexity and the Irregular Past Tense in Children Who Do and Do Not Stutter(2009) Bauman, Jessica; Ratner, Nan B; Hearing and Speech Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This study examined spontaneous language samples and standardized test data obtained from 31 pairs of children who stutter (CWS), ages 25-59 months, and age-matched children who do not stutter (CWNS). Developmental Sentence Scores (DSS; Lee, 1974) as well as the relationships among age, DSS, and other standardized test scores were compared for both groups. No substantial differences were found between groups in the syntactic complexity of spontaneous language; however, the two groups show different relationships between age and DSS and between test scores and DSS. Additionally, observed differences between CWS and CWNS in patterns of past-tense errors and usage are discussed in light of a recent theoretical model of language performance in populations with suspected basal ganglia involvement (Ullman, 2004).Item Light available to the seagrass Zostera marina when exposed to currents and waves(2009) McKone, Katie Lynn; Koch, Evamaria W; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Aquatic organisms are regularly exposed to varying degrees of hydrodynamic forces such as currents and waves. Seagrasses, which are rooted in the sediment, have flexible leaves, allowing them to sway back and forth with waves and deflect with currents. Furthermore, seagrasses can acclimate to local hydrodynamic forces exerted upon them by changing their morphology, which may benefit the organism via reduced drag, but may also bring disadvantages such as increased self-shading. We examined the interaction between water flow and morphology of the seagrass Zostera marina, and how this interaction affects light availability to the plant. We also assessed carbon and nutrient content of Z. marina, as the uptake of these constituents has been linked to hydrodynamic conditions and sediment composition. Our results indicate that local hydrodynamics and sediment composition induce morphological variation in the seagrass Z. marina, and that this variation influences light availability to the seagrass canopy.Item INTERFACE EFFECTS ON NANOELECTRONICS(2009) Conrad, Brad Richard; Williams, Ellen D; Physics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Nanoelectronics consist of devices with active electronic components on the nanometer length scale. At such dimensions most, if not all, atoms or molecules composing the active device region must be on or near a surface. Also, materials effectively confined to two dimensions, or when subject to abrupt boundary conditions, generally do not behave the same as materials inside three dimensional, continuous structures. This thesis is a quantitative determination of how surfaces and interfaces in organic nanoelectronic devices affect properties such as charge transport, electronic structure, and material fluctuations. Si/SiO2 is a model gate/gate dielectric for organic thin film transistors, therefore proper characterization and measurement of the effects of the SiO2/organic interface on device structures is extremely important. I fabricated pentacene thin film transistors on Si/SiO2 and varied the conduction channel thickness from effectively bulk (~40nm) to 2 continuous conducting layers to examine the effect of substrate on noise generation. The electronic spectral noise was measured and the generator of the noise was determined to be due to the random spatial dependence of grain boundaries, independent of proximity to the gate oxide. This result led me to investigate the mechanisms of pentacene grain formation, including the role of small quantities of impurities, on silicon dioxide substrates. Through a series of nucleation, growth and morphology studies, I determined that impurities assist in nucleation on SiO2, decreasing the stable nucleus size by a third and increasing the overall number of grains. The pentacene growth and morphology studies prompted further exploration of pentacene crystal growth on SiO2. I developed a method of making atomically clean ultra-thin oxide films, with surface chemistry and growth properties similar to the standard thick oxides. These ultra-thin oxides were measured to be as smooth as cleaned silicon and then used as substrates for scanning tunneling microscopy of pentacene films. The increased spatial resolution of this technique allowed for the first molecular resolution characterization of the standing-up pentacene crystal structure near the gate dielectric, with molecules oriented perpendicular to the SiO2 surface. Further studies probed how growth of C60 films on SiO2 and pentacene surfaces affected C60 morphology and electronic structure to better understand solar cell heterojunctions.Item Lexical Structure and the Nature of Linguistic Representations(2006-08-09) Fiorentino, Robert D.; Poeppel, David; Linguistics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation addresses a foundational debate regarding the role of structure and abstraction in linguistic representation, focusing on representations at the lexical level. Under one set of views, positing abstract morphologically-structured representations, words are decomposable into morpheme-level basic units; however, alternative views now challenge the need for abstract structured representation in lexical representation, claiming non-morphological whole-word storage and processing either across-the-board or depending on factors like transparency/productivity/surface form. Our cross-method/cross-linguistic results regarding morphological-level decomposition argue for initial, automatic decomposition, regardless of factors like semantic transparency, surface formal overlap, word frequency, and productivity, contrary to alternative views of the lexicon positing non-decomposition for some or all complex words. Using simultaneous lexical decision and time-sensitive brain activity measurements from magnetoencephalography (MEG), we demonstrate effects of initial, automatic access to morphemic constituents of compounds, regardless of whole-word frequency, lexicalization and length, both in the psychophysical measure (response time) and in the MEG component indexing initial lexical activation (M350), which we also utilize to test distinctions in lexical representation among ambiguous words in a further experiment. Two masked priming studies further demonstrate automatic decomposition of compounds into morphemic constituents, showing equivalent facilitation regardless of semantic transparency. A fragment-priming study with spoken Japanese compounds argues that compounds indeed activate morphemic candidates, even when the surface form of a spoken compound fragment segmentally-mismatches its potential underlying morpheme completion due to a morpho-phonological alternation (rendaku), whereas simplex words do not facilitate segment-mismatching continuations, supporting morphological structure-based prediction regardless of surface-form overlap. A masked priming study on productive and non-productive Japanese de-adjectival nominal derivations shows priming of constituents regardless of productivity, and provides evidence that affixes have independent morphological-level representations. The results together argue that the morpheme, not the word, is the basic unit of lexical processing, supporting a view of lexical representations in which there are abstract morphemes, and revealing immediate, automatic decomposition regardless of semantic transparency, morphological productivity, and surface formal overlap, counter to views in which some/all complex words are treated as unanalyzed wholes. Instead, we conclude that morphologically-complex words are decomposed into abstract morphemic units immediately and automatically by rule, not by exception.