ScholarWorks@UMassAmherst
We are now able to accept submissions directly in ScholarWorks. For submissions that are not doctoral dissertations or masters theses, please log in with your NetID, click the + (plus) in to the top left corner, and select the Submit Research option.
Graduate students filing for February 2025 degrees: We are now accepting submissions directly to ScholarWorks. Directions for submissions can be found in this guide. Please email scholarworks@library.umass.edu if you have any questions.
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Recent Submissions
Publication Surface dissipation and foliar penetration of acetamiprid on tea leaves in the presence or absence of adjuvants(2024)This study is to investigate the surface dissipation and foliar penetration of acetamiprid following application to live tea plants in the presence and absence of two adjuvants (Alligare 90 (R) (R) and Peptoil (R)). (R)). SERS mapping protocol with a self-assembled AuNP mirror as substrates was utilized for in situ and real time pesticide analysis. The surface dissipation analysis showed that acetamiprid with Alligare 90 (R) (R) had the lowest dissipation rate (34%) compared to acetamiprid alone (60%) or with Peptoil (R) (R) (44%), indicating the addition of Alligare 90 (R) (R) was more effective in reducing the surface dissipation of acetamiprid than Peptoil (R). (R). The study also investigated the foliar penetration of acetamiprid into tea leaves with and without adjuvants using SERS and LC-MS/MS. The study concludes that the two adjuvants tested can enhance spreadability, surface stability, and foliar penetration of acetamiprid applied on tea leaves. The information will facilitate the development and application of efficient and safe pesticide formulations.Publication Human activity drives establishment, but not invasion, of non-native plants on islands(2024)Island ecosystems are particularly susceptible to the impacts of invasive species. Many rare and endangered species that are endemic to islands are negatively affected by invasions. Past studies have shown that the establishment of non-native species on islands is related to native plant richness, habitat heterogeneity, island age, human activity, and climate. However, it is unclear whether the factors promoting establishment (i.e. the formation of self-sustaining populations) also promote subsequent invasion (i.e. spread and negative impacts). Using data from 4308 non-native plant species across 46 islands and archipelagos globally, we examined which biogeographic characteristics influence established and invasive plant richness using generalized linear models nested within piecewise structural equation models. Our results indicate that anthropogenic land use (i.e. human modification) is strongly associated with establishment but not invasion, that climate (maximum monthly temperature) is strongly associated with invasion but not establishment, and that habitat heterogeneity (represented by maximum elevation and island area) is strongly associated with both establishment and invasion. Island isolation explains native plant richness well, but is not associated with established and invasive plant richness, likely due to anthropogenic introductions. We conclude that anthropogenic land use on islands is likely to be a proxy for the number of introductions (i.e. propagule pressure), which is more important for establishment than invasion. Conversely, islands with more diverse habitats and favorable (warm) climate conditions are likely to contain more available niche space (i.e. 'vacant niches') which create opportunities for both establishment and invasion. By evaluating multiple stages of the invasion process, we differentiate between the biogeographic characteristics that influence plant establishment (which does not necessarily lead to ecological impacts) versus those that influence subsequent plant invasion (which does lead to negative impacts).Publication Helical close-packing of anisotropic tubes(2024)Helically close-packed states of filaments are common in natural and engineered material systems, ranging from nanoscopic biomolecules to macroscopic structural components. While the simplest models of helical close-packing, described by the ideal rope model, neglect anisotropy perpendicular to the backbone, physical filaments are often quite far from circular in their cross-section. Here, we consider an anisotropic generalization of the ideal rope model and show that cross-section anisotropy has a strongly non-linear impact on the helical close-packing configurations of helical filaments. We show that the topology and composition of the close-packing landscape depends on the cross-sectional aspect ratio and is characterized by several distinct states of self-contact. We characterize the local density of these distinct states based on the notion of confinement within a 'virtual' cylindrical capillary, and show that states of optimal density vary strongly with the degree of anisotropy. While isotropic filaments are densest in a straight configuration, any measure of anisotropy leads to helicity of the maximal density state. We show the maximally dense states exhibit a sequence of transitions in helical geometry and cross-sectional tilt with increasing anisotropy, from spiral tape to spiral screw packings. Furthermore, we show that maximal capillary density saturates in a lower bound for volume fraction of pi/4 in the large-anisotropy, spiral-screw limit. While cross-sectional anisotropy is well-known to impact the mechanical properties of filaments, our study shows its strong effects to shape the configuration space and packing efficiency of this elementary material motif.Publication Protecting migrant children's well-being in Ecuador's public schools(2024)Education plays a crucial role in the adaptation and broader societal inclusion of immigrant students and their families. The current study explored the inclusion of migrants in Ecuador's school system as a fundamental tenet of protecting their health and well-being. We conducted a thematic analysis of 13 policy documents, 12 national laws and international agreements, and 31 key informant interviews, applying a human rights lens. We find that, although the 2008 Ecuadorian Constitution and migration laws protect the right of migrants to health and education, key informants argue that these laws are poorly implemented. Furthermore, they agree that the health sector generally does not consider education as a relevant setting for health. In contrast, the public education sector and non-profit organizations at the national and local levels appear to recognize the importance of coordination across the health and education sectors, including school-based initiatives for migrant inclusion.Publication Collagen structures of demineralized bone paper direct mineral metabolism(2024)Bone is a dynamic mineralized tissue that undergoes continuous turnover throughout life. While the general mechanism of bone mineral metabolism is documented, the role of underlying collagen structures in regulating osteoblastic mineral deposition and osteoclastic mineral resorption remains an active research area, partly due to the lack of biomaterial platforms supporting accurate and analytical investigation. The recently introduced osteoid-inspired demineralized bone paper (DBP), prepared by 20-mu m thin sectioning of demineralized bovine compact bone, holds promise in addressing this challenge as it preserves the intrinsic bony collagen structure and retains semi-transparency. Here, we report on the impact of collagen structures on modulating osteoblast and osteoclast-driven bone mineral metabolism using vertical and transversal DBPs that exhibit a uniaxially aligned and a concentric ring collagen structure, respectively. Translucent DBP reveals these collagen structures and facilitates longitudinal tracking of mineral deposition and resorption under brightfield microscopy for at least 3 wk. Genetically labeled primary osteogenic cells allow fluorescent monitoring of these cellular processes. Osteoblasts adhere and proliferate following the underlying collagen structures of DBPs. Osteoblastic mineral deposition is significantly higher in vertical DBP than in transversal DBP. Spatiotemporal analysis reveals notably more osteoblast adhesion and faster mineral deposition in vascular regions than in bone regions. Subsequent osteoclastic resorption follows these mineralized collagen structures, directing distinct trench and pit-type resorption patterns. In vertical DBP, trench-type resorption occurs at an 80% frequency, whereas transversal DBP shows 35% trench-type and 65% pit-type resorption. Our studies substantiate the importance of collagen structures in regulating mineral metabolism by osteogenic cells. DBP is expected to serve as an enabling biomaterial platform for studying various aspects of cellular and extracellular bone remodeling biology. While the mechanisms of bone mineral metabolism are known, the role of underlying collagen structure in directing osteogenic cellular processes remains an active research area due to the difficulty of monitoring these processes inside the bone cavity. In this study, we demonstrate the significance of collagen structure in modulating osteoblastic mineral deposition and osteoclastic mineral resorption using demineralized bone paper (DBP) created by thin slicing of demineralized bovine bone matrix. DBP preserves the natural collagen structure and retains semi-transparency for microscopic imaging, displaying distinct patterns based on vertical and transversal sectioning directions. Osteoblast adhesion and mineral deposition occur following the collagen structure, with vertical DBP supporting higher mineral deposition compared with transversal DBP. Osteoclast mineral resorption also follows these collagen patterns, with vertical DBP exhibiting higher trench-type resorption, while transversal DBP shows more pit-type resorption. This study underscores the importance of collagen structure in directing bone metabolism. We envision that DBP as a valuable tool for studying bone mineral metabolism and related processes.
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