74201 research outputs found
Sort by
Decellularized Tooth Bud ECM Silk Scaffolds promote Dental Cell Differentiation
No full textAbstract: There are multiple causes of tooth loss can be caused by multiple reasons, including caries, periodontal disease, trauma and genetic disease. The dental pulp has important functions to sustain teeth, by providing nutrient and oxygen supply, innervation and immune response. Our objective was to determine whether incorporating extracellular matrix derived from decellularized pig tooth buds (tECM) into silk scaffolds would enhance dental pulp derived dental mesenchymal stem cell (DMSC) differentiation. Nine different types of silk scaffolds were fabricated: 1) 6% silk; 2) 6% silk+tECM; 3) 6% silk+collagen; 4) 3% silk, 4g salt; 5) 3% silk, 4g salt + tECM; 6) 3% silk, 4g salt + collagen; 7) 3% silk, 2g salt; 8) 3% silk, 2g salt + tECM; and 9) 3% silk, 2g salt + collagen. Unseeded silk scaffolds were used as controls. Three replicates were used for each experimental condition and controls. Porcine DMSCs (pDMSCs) at passage 2 were seeded into silk scaffolds (3x105 cells/scaffold, ~3x103cells/mm3) and cultured in vitro in osteogenic media for 24 hours, or for 2 and 4 weeks. Histological analyses of paraffin embedded and sectioned constructs revealed pDMSC attachment and proliferation after two and four-week in vitro culture. Immunofluorescent (IF) analysis showed robust dentin sialoprotein (DSP) expression in all pDMSC seeded silk scaffolds. DSP expression was enhanced in scaffolds containing tECM. Statistical analysis demonstrated significant differences in DSP expression in scaffolds with versus without tECM (P≤0.01). Silk scaffolds supported the attachment, proliferation and differentiation of seeded pDMSCs. Furthermore, our research is the first study to demonstrate that tECM can enhance the pDMSC differentiation, suggesting that tECM incorporated scaffolds show promise for dental pulp and/or whole tooth regeneration. Studies of in vivo implanted constructs are being performed to further investigate the effect of tECM on DMSC differentiation and mineralized tissue formation. Keywords: silk scaffolds, decellularized tooth bud scaffolds, pulp regeneration, dental stem cells Support: This research was supported by NIH/NIDCR/NIBIB Award R01DE016132 (PCY).Thesis (M.S.)--Tufts University, 2018.Submitted to the Dept. of Orthodontics.Advisor: Pamela Yelick.Committee: Carroll Ann Trotman, Weibo Zhang, and Sarah Pagni.Keywords: Dentistry, and Biology
Selecting a Method of Data Collection.
No full textThis Presentation was given at First National Workshop in Nepal on Data Collection method
THE DEVELOPMENT OF ACADEMIC ENGAGEMENT AMONG YOUTH IN CHINA: MIGRANT STATUS AS A MODERATOR
No full textAbstract: Based on an integrative framework of motivational theories, the present study investigates the development of academic engagement among a nationally representative sample of early adolescents in China (N = 1136; 49.34% girls; average age at Wave 1 is 11.51 years, SD = .57 years). Specifically, using latent growth curve models and multi-group structural equation analysis, the present study examines how migrant status contributes to different developmental patterns of academic engagement. In addition, using longitudinal mediation models, I explore the extent to which caregiver involvement in education is associated with students' academic self-concept to promote academic engagement, and how such associations are moderated by migrant status. I find that the developmental trajectories of academic engagement are moderated by students' migrant status. Moreover, migrant status moderates the associations among caregiver involvement, academic self-concept, and academic engagement. Compared to migrant and urban youths, left-behind youths and status rural youths experience significantly lower but more stable academic engagement over time. Furthermore, caregiver involvement is less likely to predict academic self-concept and academic engagement among left-behind youths and status rural youths than other migrant groups. This research provided empirical insights into the underlying processes of academic engagement among Chinese adolescents and the roles of migrant status. Research and policy implications are discussed.Thesis (Ph.D.)--Tufts University, 2018.Submitted to the Dept. of Child Development.Advisor: Calvin Gidney.Committee: Tama Leventhal, Jonathan Zaff, and David Osher.Keywords: Developmental psychology, Educational psychology, and Secondary education
Mega projects: Worth the Cost? A Study of Three Boston Mega projects and Their Impact on Their Neighborhoods.
No full textAbstract: Abstract: This thesis asks the question: why do urban megaprojects create a negative public perception for staying on budget, and seeks to determine if the economic gain for the city is worth the cost despite the potential backlash and setbacks? To answer this question, we examined three cases studies in the City of Boston: The West End Redevelopment, The John B. Hynes Auditorium (now the John B. Hynes Convention Center) and the Seaport World Trade Center. They have been selected based on the simple fact that they have had time to mature and that there is historical data to support claims of economic success or failure. Each of these projects was funded by a mixture of public and private funds, were met with moderate to severe resident opposition, encountered multiple hiccups and setback, and changed the shape of the neighborhoods in which they were built. Despite this, all produced ongoing benefits for the Boston in terms of property values, increased taxes, jobs, and revitalization of dilapidated areas. There was, however, significant differences in how much economic benefit was captured in each project. This should be dependent on what the area looked like before the projects, and how the project was executed. While mega projects might, universally, produce some economic benefit, certain projects can truly justify their cost, while others do not.Thesis (M.A.)--Tufts University, 2018.Submitted to the Dept. of Urban and Environmental Policy and Planning.Advisors: Justin Hollander, and Sumeeta Srinivasan.Keyword: Urban planning
Information Geometry for Model Reduction in Power Systems
No full textAbstract: Load modeling has been extensively studied to understand the behavior of power systems. The essential problem of load modeling is that it is very hard to precisely describe a large collection of heterogeneous physical devices. These devices not only have different characteristics but also change depending on the various conditions such as weather, time, economic conditions, etc. To analyze the behavior, a large number of devices are first grouped into similar loads. Then, these loads are replaced with equivalent circuits and logics for calculation. Many parameters are typically needed to describe the load characteristics. One aspect of model simplification has to do with the number of parameters, as more parameters definitely have the potential to offer better accuracy. However, more parameters will also make the system and computation more complicated. This dissertation introduces a new approach to simplify complex load models and estimate the parameters. One of emerging trends in power systems involves the use of information technology. This dissertation focuses on a method based on information geometry which combines information theory with computational differential geometry to derive global estimation results. The approach sheds a new light on difficulties commonly encountered when fitting widely used models to the measurement data. Simulations are performed based on a conventional composite load model and the new WECC Composite Load Model. The results are then compared with the full original model and the reduced parameter model to verify the effectiveness of reduction via information geometry.Thesis (Ph.D.)--Tufts University, 2018.Submitted to the Dept. of Electrical Engineering.Advisor: Aleksandar Stanković.Committee: Christoph Börgers, Usman Khan, and Mark Transtrum.Keyword: Electrical engineering
MATHEMATICAL THINKING: A SEMIOTIC COORDINATION OF IDEAL-MATERIAL COMPONENTS.
No full textA qualifying paper submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Education. Abstract: Abstract. In this case study, I provide evidence for, and operationalize (fill the gaps and provide specific analytic methods to replicate) the “dynamic unity of material and ideal components” framework for mathematical cognition (Radford, 2014, p. 268). Mathematical thinking, according to this framework, is a “semiotic coordination” (Radford, 2014, p. 268) of ideal and material components, such as speech, gestures, tactility, rhythm, perception, sensuous imagination, and actions with cultural artifacts. The analytical methods in the present case study involve a frame-by-frame analysis of data collected during an interview with a seventh grade student exploring the shadow of a figurine. In this case study, I identified the following six ideal-material components described by Radford: outer speech, gestures, tactility, rhythm, perception, and actions with cultural artifacts. To illustrate Radford’s framework, I identify ideal-material components that co-occur in space and time, discuss ways in which they might be semiotically coordinated in terms of carrying identical, supporting, complementary or additional meaning, and argue that these are the components of learner’s mathematical thinking. Lastly, I draw implications for mathematics education and research
Understanding North Korea’s Cyber Operations.
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: It is almost a daily routine to read in newspaper about North Korean hacking. The most renowned case is Sony Pictures Entertainment cyberattack on the eve of releasing The Interview. However, Sony Pictures Entertainment seems to be the beginning of North Korean activities in cyberspace. Pyongyang hacks e-mails and defense ministry’s internal networks, steals military operation plan jointly devised by allies, and robs financial institutions with limited success. What is North Korea doing in cyberspace? Is Pyongyang acting irrationally in cyberspace, as it seems to be in non-cyberspace? What is Pyongyang’s goals and objectives in its cyber operations? And how should we address increasing North Korean threat? The paper argues that North Korean cyber hacks are consistent with its greater strategy to secure regime survival by protecting legitimacy of Kim regime, boosting economy by any means and provoking to advance conventional deterrence against its adversaries
Knowing How to Go on: Modernism and the Ordinary Uses of Language
No full textAbstract: Many literary scholars consider the distinguishing marks of modernism to be its unconventional uses of language, particularly as this unconventional language shows the failure of representation and communication. This failure is thus seen as a critique of meaning, conceptual stability, and knowledge. The writers in this study—Oscar Wilde, Joseph Conrad, Nella Larsen, and Samuel Beckett—offer some examples of the difficulties, obscurities, and logical confusions of the rules of language, and in this way they are typical of avant-garde writers of the modernist period. I argue that their concern with rule-following behaviors extends beyond the breakdown of language to understand how we know how to go on even without absolute meaning, conceptual stability, and knowledge. This claim relies on the ideas of modernist writers' philosophical contemporaries in the schools of pragmatism and ordinary language philosophy. These schools break from assumptions that language should correspond with objects and thoughts, and instead propose that the meaning of language is in its use. Language remains useful even when it is illogical, extremely complex, changeable, and contingent on situations and speakers. The chapters of this dissertation examine the uses of language in modernist fictions that present scenes of uncertainty. In the first chapter, I look to Wilde to understand how linguistic conventions can be used to satisfy desires and produce favorable consequences, but also how they keep speakers tethered to reality. In the second chapter, I show how Joseph Conrad holds on to the possibility of truth in as a reflection of shared forms of life. In the third chapter, I turn to Nella Larsen's Passing to see the value of practical certainty for social interactions and for coping with conceptual ambiguity. In the fourth chapter, I look to Samuel Beckett's Three Novels to understand how modernist fiction challenges its readers to rely on the resources of our ordinary language, even when that language frustrates logical and contextual explanations. Changing the picture of language that underlies our understanding of modernism challenges scholars to consider the many ways readers go on reading and making meaning despite the uncertainties that puncture theoretical and historical explanations.Thesis (Ph.D.)--Tufts University, 2018.Submitted to the Dept. of English.Advisor: John Lurz.Committee: Modhumita Roy, Ichiro Takayoshi, and Lisi Schoenbach.Keywords: English literature, Modern literature, and Philosophy
O-Glycosylation and a Novel Bioengineered 3D Human Intestinal Tissue Model for Cryptosporidium
No full textAbstract: Cryptosporidium spp. are the causative agents of diarrheal disease worldwide, with the greatest burden on the immune-compromised and malnourished young children in resource poor countries. In vitro culture models to study this parasite with physiological relevance to in vivo infection remain sub-optimal. Thus, the pathogenesis of cryptosporidiosis remains poorly characterized, and interventions for the disease are limited. The lack of effective treatments makes the study of this organism and the development of new interventions of the utmost importance. Cryptosporidium employs mucin-like glycoproteins to attach to and infect host intestinal epithelial cells. O-glycans, specifically the Tn antigen (GalNAc 1-Ser/Thr) on these glycoproteins have been shown to be essential for these processes as a Tn-specific antibody and Tn-specific lectins block attachment and irreversibly inhibit infection. However, the enzymes catalyzing their synthesis have not been studied. Previously, we identified four genes encoding putative polypeptide N-acetylgalactosaminyl transferases (ppGalNAc-Ts) in the genomes of three Cryptosporidium spp. My project focused on the in silico analysis, cloning, expression, purification and characterization of one of the four ppGalNAc-Ts within C. parvum, Cp-ppGalNAc-T4. This enzyme contains the characteristic domains and motifs conserved in ppGalNAc-Ts family enzymes and is expressed at multiple time points during in vitro infection. Soluble, recombinant Cp-ppGalNAc-T4 functions primarily as an "initiating" enzyme with a strong preference for UDP-GalNAc over other nucleotide sugar donors. Given the importance of mucin type-O-glycosylation within Cryptosporidium spp., the enzymes that catalyze their synthesis may serve as potential therapeutic targets. While characterizing mucin-like glycoproteins and enzymes that glycosylate them is important, the lack of robust in vitro culture systems remains a serious impediment to fully understanding their function and hinders screening of potential interventions which target them. We evaluated the potential of a novel bioengineered three-dimensional (3D) human intestinal tissue model to support long-term infection by C. parvum. We found that C. parvum infected and developed in this model for at least 17 days. Contents from infected 3D tissue models could be transferred to fresh 3D tissue models to establish new infections for at least three rounds. Asexual and sexual stages and the formation of new oocysts were observed during the course of infection. We further improved the model by using human intestinal stem-cell derived "enteroids" to replace the transformed cell lines. Ultimately, a 3D model system capable of supporting continuous Cryptosporidium infection will be a useful tool for further advancing the study of host-parasite interactions, identification of putative drug targets, screening of potential interventions, and propagation of wild type and genetically modified Cryptosporidium strains.Thesis (Ph.D.)--Tufts University, 2018.Submitted to the Dept. of Immunology.Advisors: Honorine Ward, and Mercio PereiraPerrin.Committee: Stephen Bunnell, Noorjahan Panjwani, Ananda Roy, and Marc-Jan Gubbels.Keywords: Parasitology, Biochemistry, and Biomedical engineering
The Placebo Effect in a Dish: Implications for Underlying Subcellular Mechanisms
No full textAbstract: The placebo effect is well known as one of the founding premises for FDA-sanctioned clinical trials of new medications, yet there is very little scientific understanding of the cellular substrates of the phenomenon and lack of predictive biomarkers for the strength of the placebo response. Few prior correlative studies on the neurobiology of the placebo effect suggests the activation of central dopamine neurotransmission during a placebo response. The present project intends to identify the cellular and molecular mechanisms that are linked to the placebo effect in peripheral paracrine and central monoamine-secreting cells. We follow an innovative and unconventional approach in trying to induce neurotransmitter release as a response to an inert stimulus in primary dissociated cells in culture. At this first stage of our studies, we chose to conduct our experiments in rat adrenal chromaffin cells which are considered an excellent model of exocytosis for catecholamine-releasing neurons and at the same time are crucially involved at the systems level in setting the sympathetic tone and in disorders like the Cushing syndrome and hyperprolactinemia. We use the cutting-edge method of carbon fiber amperometry to assess catecholamine quantal release in real time in response to a high potassium stimulating solution in physiological temperature (37oC). Following two stimulations within 10 minutes, we expose each chromaffin cell to only a physiological temperature saline and assess release of catecholamine quanta by cells based on the prior association between the active secretagogue and physiological temperature. Cells are otherwise bathing in room temperature aCSF media. We predict that the cells predisposed to a placebo response will release catecholamine quanta when exposed to physiological temperature saline without the active secretagogue. We then proceed to identify differences in catecholamine kinetics and vesicular stores involved in the release of quanta from placebo prone cells versus non-responding cells. The above study represents the first effort to describe the molecular signature of the placebo effect in an animal and cellular model. The end overall objective of such an effort would be the development of a screening assay for human patients identifying biomarkers for the potential of a placebo therapy in advance.Thesis (M.S.)--Tufts University, 2018.Submitted to the Dept. of Pharmacology and Drug Development.Advisor: Emmanuel Pothos.Keywords: Pharmacology, and Neurosciences