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Zwitterionic Copolymers for Fouling Resistant and Responsive Membranes
No full textAbstract: Fouling is likely the most important obstacle to the use of membranes in many applications, especially in those that the feed contains high concentrations of organics such as oil and biomacromolecules. This thesis focuses on the use of zwitterionic copolymers, which are known to show excellent fouling resistance and hydrophilicity, to enhance the fouling resistance of ultrafiltration (UF) membranes and/or incorporate responsive features into these systems that can enable self-cleaning mechanisms. One approach to incorporate these features into UF membranes is during their manufacture, by blending a commodity polymer with a zwitterion containing copolymer. We synthesized random copolymers incorporating two different zwitterionic groups, sulfobetaine methacrylate (SBMA) and sulfobetaine-2-vinylpyridine (SB2VP). We showed that, with the appropriate choice of parameters, zwitterionic additive content as low as 10 wt.% can lead to membranes with high flux and complete fouling resistance to oil suspensions and protein solutions. We also studied the effect of the skeletal architecture of zwitterionic additives in membrane properties, by comparing zwitterionic copolymers with two different architectural structures, random and comb-shaped. We showed that both additives lead to a water permeance five times that of the additive free membrane. However, comb additive containing membrane exhibits a more prominent ionic strength responsive change in its surface nanostructure and permeance, in addition to its better resistance to oil fouling and protein adhesion. As another approach, we developed a novel self-cleaning, photoresponsive membrane that is capable of removing pre-deposited foulant layers upon changes in surface morphology in response to UV or visible light irradiation. This membrane was prepared by coating a porous support membrane with a thin layer of a comb-shaped graft copolymer with photoreactive side-chains. Before any photo-treatment, the as-coated membrane allows the adsorption of organic solutes on its surface, reducing flow rate. Once exposed to UV light, conversion of hydrophobic spiropyran groups to hydrophilic merocyanine groups leads to the release of adsorbed molecules and full recovery of the initial water flux. Lastly, we developed selective thin films whose morphology and function arise from the self-assembled nanostructure of the zwitterionic comb copolymers. Thin film morphology showed hierarchical features including 17 ± 5 nm spherical micelles along with larger nanopores of 85 ± 45 nm, which arose from the self-assembly of the copolymer in this bilayer system. In addition, the film proved ionic strength responsive permeation in ultrafiltration range with a pore density as high as 1013 pores/m2.Thesis (Ph.D.)--Tufts University, 2018.Submitted to the Dept. of Chemical and Biological Engineering.Advisor: Ayse Asatekin.Committee: Matthew Panzer, Samuel Thomas III, and Scott Husson.Keywords: Chemical engineering, Polymer chemistry, and Materials Science
Nonlinear label free optical imaging for morpho-functional cellular and tissue diagnosis.
No full textAbstract: Tissue imaging lies in the heart of patient care. In fact, cyto-histopathological diagnostic imaging, through the microscopic examination of cellular and tissue samples, is considered an essential component of clinical care as a diagnostic and pathognomonic aid. Traditional pathology is inherently invasive as it de facto requires the removal of the biological sample from the human body. Moreover, the necessary incorporation of processing steps, including those with fixatives and staining agents, not only delays the diagnostic outcome, but also introduces biochemical artifacts such as loss of tissue components, tissue shrinkage and constituent cross-linking. It is thus evident that standard cyto-histopathological evaluation, despite its undisputable contributions to patient care, is unable to study the dynamic nature of physiological and pathophysiological processes in an unperturbed, real-time, in situ manner. Novel optical imaging modalities offer the unique opportunity to obviate the need for tissue excision and enable non-destructive, in-vivo morpho-functional analysis. Nonlinear optical imaging (NLO) embodies an assortment of powerful microscopy techniques that generate high-contrast, high-resolution, three-dimensional imaging by exploiting nonlinear, high-order light-matter processes. The application potential of NLO multi-photon microscopy (MPM), through two-photon excited fluorescence (TPEF), fluorescence Lifetime Microscopy (FLIM) and second harmonic generation (SHG) imaging, represents the emphasis of this dissertation. Numerous applications are explored in the context of characterizing intracellular or extracellular morpho-functional changes for diagnostic, monitoring and treatment related biomedical applications in a noninvasive, label-free, unperturbed manner in situ. These cover complex and heterogeneous spatiotemporal biological systems in vitro, ex vivo and in vivo and ultimately lead to the diagnostic evaluation of all levels of cancerous progression (pre-cancer, invading cancer, metastasis) in human tissues. Ultimately this dissertation aims to highlight that the knowledge gained from elucidating the morpho-functional interplay of tissue homeostasis and disease progression through noninvasive NLO multi-photon imaging, may play a transformative role in the pathophysiological mechanistic understanding of tissue biology and in the development of improved diagnostic systems and therapeutic regimens in a broad range of biomedical and clinical applications.Thesis (Ph.D.)--Tufts University, 2018.Submitted to the Dept. of Biomedical Engineering.Advisor: Irene Georgakoudi.Committee: Bruce Tromberg, Sergio Fantini, and Thomas Schnelldorfer.Keywords: Biomedical engineering, and Optics
The Man Within: Depictions of Blackness in Superhero Adaptations
No full textAbstract: Superheroes star in simultaneously moral, secular, and entertaining stories. Introducing race into comics complicates the moral structures that dominate these worlds. This thesis explores how the representations of race and racial politics undergo mutation when superhero comics are adapted into other forms of media. I examine how the representational languages of film, television, and videogames frame and depict black superheroes. The interdisciplinary scope of this project requires an equally interdisciplinary methodology. Uniting the close reading practices of film and English studies with the body-centric approach of performance studies, I am able to unpack the metaphoric constructions of race found in my case studies. The findings show that while the superhero genre stratifies race, it is possible for black superheroes to resist these power structures. Narrative marginalization often maintains the racial status quo for black superheroes. Greater opportunities for resistance appear as black superheroes move closer to the center of narratives.Thesis (M.A.)--Tufts University, 2018.Submitted to the Dept. of Drama.Advisor: Noe Montez.Committee: Kareem Khubchandani, and Tasha Oren.Keywords: African American studies, Film studies, and American studies
Impact of the Adoption of EV on Beijing Air Quality
No full textAbstract: Air quality in Beijing has been questioned for years since 2008 Olympic Game. Recently, government implemented multiple measures to address this issue. Plate registration restriction was announced in the 2010 and in 2014, there was a major change to the policy to promote electric vehicles. Electric vehicle buyers did not have to join the same lottery pool as other buyers after that. The impact of an electric vehicle on the air quality depends on reginal generation mix and Beijing is highly relied on fire power plants. This paper will empirically analyze the impact of this adoption policy by examining the relationship between air quality after 2014 and lottery results. The outcome shows that there is little effect from the policy but power plants exhibit significant impact on the air quality.Thesis (M.S.)--Tufts University, 2018.Submitted to the Dept. of Economics.Advisor: Ujjayant Chakravorty.Committee: Kelsey Jack, and Gilbert Metcalf.Keyword: Economics
"We Join to be Challenged, We Don't Join to be Victims": Mapping Experiences of Women in the U.S. Military.
No full textSubmitted in partial fulfillment of the degree Master of Arts in Law and Diplomacy at the Fletcher School of Law and Diplomacy. Abstract: Military servicewomen live with coexisting identities that are dissonant with conventional gender roles. There are nearly two million women veterans in the United States, comprising the fastest growing population of veterans in the nation. Women are promised at enlistment or commissioning that there is a place for them in the brotherhood, only to find that women are constant outsiders. Servicewomen are isolated, and misunderstood by both the institution in which they serve, and by the society they are sworn to protect. It is why, 70% of the two million living American women who served in the military do not self-identify as veterans. Combining perspective written by woman veteran and social science researcher, this Capstone captures the voices of hundreds of women veterans who feel invisible and misunderstood. Three key milestones of women’s military service communicate that women are constant outsiders: boot camp, a mid-career institutional betrayal, and experiences after separation that reinforce previous experiences of “otherness”. This paper combines feminist theory, empirical data, policy recommendations, and also poses questions about how academic research can help servicewomen and women veterans find their own voices to understand and contextualize their experiences
Implicit Ambivalent Racist Sexism: An Intersectional Approach to Racial and Gender Bias.
No full textThis study investigates the implications of racial preference in relation to ambivalent sexism
Functional Polymer Membranes for Heavy Metal Removal.
No full textThe ability of COOH-functional polymer membranes previously described by Sadeghi et al. to remove metals from water was investigated. Through static adsorption tests, it was found that these membranes have functional layers with capacities comparable to other previously described adsorptive materials, but lower. Pressure-driven filtration tests were performed, which showed breakthrough curves with some residual rejection. The capacities calculated with the breakthrough curves reasonably matched those found by static adsorption and the steady-state rejections shown matched those of previously reported charge-based rejection modes. The ability of acid to regenerate these membranes was also investigated. It was found that the membranes were stable at pH 3 and that soaking in acid was sufficient to remove the metal ions bound to the membranes, allowing the membranes to be reused. Some properties of SH-functional membranes were also investigated. First, they were prepared using EDC/NHS coupling to attach SH-terminal groups to the free carboxylic acid groups on the membrane pore surface. Then, the ability of these new membranes to remove metals was investigated in static adsorption. It was found that although the SH-functional membranes did not adsorb as much metal as the COOH-functional ones, they showed a selectivity against calcium, which is useful for applications involving removal of heavy metal contaminants from hard water. Both types of membrane exhibited show promise for the ability to remove potentially hazardous heavy metal ions from water
Improving Estimations of Inherent Optical Properties in Coastal Ocean Color Modeling.
No full textSynoptic, satellite-derived estimates of phytoplankton biomass from ocean color have significantly advanced our understanding of biological oceanography. However, the algorithms that translate ocean color to phytoplankton biomass and other water quality metrics have severely diminished accuracy in coastal and estuarine ecosystems due to high and variable concentrations of suspended sediment and dissolved organic matter. Field sampling within the Chesapeake Bay indicates particulate backscattering and total absorption significantly covary as a function of salinity. This field data includes water quality, optical, and in situ remote sensing measurements previously collected from the Choptank River, a Chesapeake Bay tributary, along with the Bay itself to sample a broad range of optical and estuarine conditions. Improvements in the estimation of absorbance and backscattering will significantly improve the performance of current ocean color models in the estimation of phytoplankton absorption from satellite imagery in the optically complex waters of the Chesapeake Bay. Towards this end, empirical correlations between these two optical parameters were derived as a function of salinity, to reflect how these parameters change along the Chesapeake Bay estuary. These relationships were then incorporated with spatial salinity data to build a steady-state geospatial model to predict these parameters within the Choptank River during summer conditions. This model sets the groundwork for a real-time predictive model to incorporate into current remote sensing algorithms, improving day-to-day satellite measurements. In addition, this model could be used to investigate the impacts of larger temporal processes, such as El-Nino Oscillations and climate change, on these optical properties and the field of coastal remote sensing as a whole
History and Memory in Chilean Unions: Continuity and Contradiction from their Origins through Today.
No full textAn exploration of the history and memory of Chilean labor unions and how union leader's understanding of the strength of the movement in the past contributes to their understanding of the strength of the movement today