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Title: Development of a work-based learning model for youth with disabilities from the perspective of employers
Creator: Sametz, Rebecca R.
Date: 2017
Collection: Electronic Theses & Dissertations
Description: ABSTRACTDEVELOPMENT OF A WORK-BASED LEARNING MODEL FOR YOUTH WITH DISABILITIES FROM THE PERSPECTIVE OF EMPLOYERSBy Rebecca R. Sametz For youth with disabilities, transitioning from school to work and adult life often means overcoming multiple social, academic, and environmental constraints that may present as roadblocks to meeting society’s expectations of ‘successful transition’ (Lehman, Clark, Bullis, Rinkin, & Castellanos, 2002). According to the United States Department of Labor (2014),...
Show moreABSTRACTDEVELOPMENT OF A WORK-BASED LEARNING MODEL FOR YOUTH WITH DISABILITIES FROM THE PERSPECTIVE OF EMPLOYERSBy Rebecca R. Sametz For youth with disabilities, transitioning from school to work and adult life often means overcoming multiple social, academic, and environmental constraints that may present as roadblocks to meeting society’s expectations of ‘successful transition’ (Lehman, Clark, Bullis, Rinkin, & Castellanos, 2002). According to the United States Department of Labor (2014), the employment rate for youth with disabilities between the ages of 16 and 19 was 16.6% and the employment rate of 16-19-year-old youth without disabilities was 29.9%. In total, that is a 13.3% difference in the rate of employment for youth with disabilities compared to youth without disabilities of the same age. Further, the employment rate of youth with disabilities between the ages of 20 and 24 was 31.6% while the employment rate of youth without disabilities of the same age was 65.0% which is a difference of 33.4% between 20-24-year-old youth with and without disabilities. A gap remains when comparing youth with disabilities to the general youth population on factors such as high school graduation rates, readiness for the world of work, post-secondary education participation, employment rates, wages, and poverty levels (Turner, 2007). Further, a lack of alignment of the employer needs and expectations from employers is a shortcoming that is frequently encountered in the transition process (Rutkowski, Daston, Van Kuiken, & Riehle, 2006). To address the unemployment gap, work-based learning has been deemed an opportunity for youth with disabilities to apply academic and vocational skills and knowledge to real work situations as they develop the attitudes, values, problem solving skills, and behaviors that will help them in their transition from school to the world of work and adult life (Burgstahler, 2001). This study was conducted using qualitative methods to explore and describe employer perceptions of work-based learning in order to develop a conceptual model of work-based learning for youth with disabilities. Interviews were conducted with eight participants who were currently or previously involved in participating in a work-based learning program for youth with disabilities in the Lansing, Michigan area. Data for the current study was collected using semi-structured interviews that were done face-to-face with participants. The results of the study stress how employers describe work-based learning; and what factors do employers believe are important in the successful execution of a work-based learning program for youth with disabilities. From the results, participant’s responses were coded into five major themes: role of employer, critical factors, key stakeholders, targeted program outcomes, and challenges to program implementation. Additionally, a conceptual model emerged from the results of the study to help describe employers’ perceptions on work-based learning programs for youth with disabilities. Implications for practice, policy, and future research are discussed.
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Title: Stories of Cuban-Americans living and learning bilingually
Creator: Perez, Natasha
Date: 2017
Collection: Electronic Theses & Dissertations
Description: This study explores the interplay of bilingualism, identity, literacy and culture for Cuban- American students in the Cuban diaspora. I contextualize their experiences within the social, historical, and political background of Cuban immigration, situating their stories within the conflicting narratives of Cuban-American imagination in the U.S., to explore how manifestations of Cubania shape the language and literacy practices of Cuban-American youth across generations and contexts, within...
Show moreThis study explores the interplay of bilingualism, identity, literacy and culture for Cuban- American students in the Cuban diaspora. I contextualize their experiences within the social, historical, and political background of Cuban immigration, situating their stories within the conflicting narratives of Cuban-American imagination in the U.S., to explore how manifestations of Cubania shape the language and literacy practices of Cuban-American youth across generations and contexts, within three U.S. states.Inspired by traditions of phenomenology and narrative inquiry (Clandelin & Connoly, 2000), this study is an intentional narrative "reconstruction of a person's experience in relationship both to the other and to a social milieu" (CC 200-5), drawing from three narratives of experience, including my own. The three narratives are based on the experiences Cuban- American adolescent girls growing up in different contexts, in search of answers to the following questions:a) For each participant in this study, what are the manifestations of Cuban identity, or Cubania? b) What are the factors that sustain different or similar manifestations of Cubania, both within and across generations of immigrants? c) How, if at all, do manifestations of Cubania shape the language and literacy practices of Cuban-American youth?The narratives in this study demonstrate how language, collective memory, and context become semiotic resources that come to bear on the diasporic identities of the participants. Our ideas about Cuban-ness, as well as our experience of Cuban-ness, are somewhat different,because of the ecologies in which we experienced the culture, as well as our unique family history with Cuba. The relationship between each family and their history with Cuba also shapes what Cuba is to these individuals, making it possible to have different imaginaries of Cuba, as they construct their Cuban identities based on the physical, historical, and emotional sediment that they stand on.Translanguaging emerges as a language practice that provides key opportunities to enact Cuban identity, as well as to feel connected to Cuban-ness. During times of developing proficiency, translanguaging becomes a scaffold that facilitates inclusion in conversations in their midst. For two participants, their experiences reading and discussing the bible in two languages through translanguaging serves to build and reinforce their Spanish literacy and fluency, as they use their academic language of English to inform their understanding of the Spanish bible. Thus translanguaging and religious literacies emerge as funds of knowledge and a bridge to biliteracy. However, constraints to translanguaging emerge for one participant, who has little opportunity to navigate spaces of Spanish use on her own, and becomes limited in her ability to hold conversations with Spanish speakers who cannot translanguage.This research on Cuban American students is timely, considering that Hispanics are the majority minority in public schools, and largest minority in at least twenty-two states, including states that previously had little contact with immigration at all (Pew, 2013).Such an in depth look at a small sample of students is helpful in teasing out the nuances that exist in areas that are known to be both foundational and meaningful to student success in school, such as identity and culture. However, these are nuances that are easily rendered invisible with when we engage in the project of categorization that essentializes all students as one thing or another, in this case, Spanish language heritage students as "Hispanic" or "Latino".
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Title: Integrating satellite observations into process-based models to inform agricultural water management
Creator: Deines, Jillian M.
Date: 2018
Collection: Electronic Theses & Dissertations
Description: Irrigation plays an important role in food production and the water cycle worldwide by enhancing agricultural yields, buffering climate variability, and appropriating 70% of total human freshwater use. Maintaining and even expanding irrigated areas is required to address increasing global food demand and climate-induced water stress. Over the latter half of the twentieth century, however, non-renewable groundwater use more than tripled to comprise ~1/5 of global irrigation water. As a result,...
Show moreIrrigation plays an important role in food production and the water cycle worldwide by enhancing agricultural yields, buffering climate variability, and appropriating 70% of total human freshwater use. Maintaining and even expanding irrigated areas is required to address increasing global food demand and climate-induced water stress. Over the latter half of the twentieth century, however, non-renewable groundwater use more than tripled to comprise ~1/5 of global irrigation water. As a result, key agricultural regions around the world are on unsustainable trajectories due to aquifer depletion. With limited water resources defining the 21st century, finding ways to maximize water use and operate within system boundaries is crucial. Crop and hydrology models can support decision making in the face of these challenges by simulating alternative management pathways under a range of resource conditions. In many cases, however, critical input datasets are missing or lack the precision and accuracy to fully parameterize landscape models. Recent rapid advances in large-scale satellite remote sensing can address these data gaps by quantifying landscape characteristics at previously infeasible spatial and temporal resolutions. In this dissertation, I present new methodologies that translate Landsat satellite observations into annual irrigation maps needed to understand and manage agricultural water resources. Maps are then analyzed and integrated into crop models to better understand historic water use, evaluate novel stakeholder-driven groundwater management, and support future planning. I focused on the High Plains Aquifer (HPA) in the central United States, where a $20 billion agricultural economy is threatened due to extensive depletion over much of the aquifer. In Chapter 1, I used Google Earth Engine and the full Landsat archive from 1999-2016 to generate annual, moderately high resolution (30 m) irrigation maps for the Republican River Basin portion of the HPA from 1999-2016. I found considerable interannual variability in irrigation location and extent, largely driven by annual precipitation, commodity prices, and increased irrigation efficiency over time. Chapter 2 extended this method to the full 450,000 km2 HPA from 1984-2017, addressing additional challenges from satellite data gaps and a wider range of climate, crop types, and management. I estimated that up to 24% of currently irrigated area could be lost by 2100 if aquifer depletion continues along recent trends.With increasing resource scarcity, a diverse set of groundwater management approaches have emerged across the HPA to slow depletion. In Chapter 3, I combined the satellite-derived irrigation maps, detailed well records, and national crop maps to assess the efficacy of innovative stakeholder-driven groundwater management in northwest Kansas referred to as the Local Enhanced Management Area (LEMA) program. I found that farmers surpassed targets for reduced water use without compromising irrigated area through adaptive cropping choices and increased irrigation efficiency. Chapter 4 extends the LEMA analysis with process-based crop models to robustly quantify impacts to the full water budget along with trade-offs in crop yield. Integrating remote sensing into this modeling framework allowed me to estimate quantities that are difficult or impossible to measure. As aquifer depletion threatens crop production in many parts of the world, approaches that integrate models with in-situ and remotely sensed data can improve understanding and help inform economically and hydrologically sustainable management strategies.
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Title: BIOSENSING TOTAL BACTERIAL LOAD IN LIQUID MATRICES TO IMPROVE FOOD SUPPLY CHAIN SAFETY USING CARBOHYDRATE-FUNCTIONALIZED MAGNETIC NANOPARTICLES FOR CELL CAPTURE AND GOLD NANOPARTICLES FOR SIGNALING
Creator: Matta, Leann Lerie
Date: 2018
Collection: Electronic Theses & Dissertations
Description: Economical rapid nano-biosensing methods with expedited electrochemical signaling, were developed using carbohydrate-functionalized magnetic nanoparticles (MNP) and gold-nanoparticles (AuNP) to detect pathogenic bacteria in liquid or homogenized food samples. MNP functionalized with glycan- and amino/glycan ligands were able to rapidly extract bacteria, while concentrated dextrin-coated AuNP labeling improved detection sensitivity. Carbohydrate ligands are more stable than antibodies,...
Show moreEconomical rapid nano-biosensing methods with expedited electrochemical signaling, were developed using carbohydrate-functionalized magnetic nanoparticles (MNP) and gold-nanoparticles (AuNP) to detect pathogenic bacteria in liquid or homogenized food samples. MNP functionalized with glycan- and amino/glycan ligands were able to rapidly extract bacteria, while concentrated dextrin-coated AuNP labeling improved detection sensitivity. Carbohydrate ligands are more stable than antibodies, permitting long shelf life of MNP at room temperature and minimized AuNP aggregation during simple refrigeration. Transmission electron microscopy (TEM) imaged the electrostatic binding between MNP and Salmonella Enteritidis, E. coli O157:H7, Bacillus cereus, Listeria monocytogenes and E. coli C3000, which mimics electrostatic binding by antibodies, although with lower specificity. Capture index (CI) is defined as the parts-per-thousand (ppt) of bacteria extracted per initial bacterial presence. TEM mages showed that attached milk matrix components did not interfere with microbial. capture. Salmonella, E. coli, and Bacillus (3 to 5 log CFU/mL) capture in three milks was 2 ppt to 120 ppt CI. Capture in beef juice and apple cider was 0.002 ppt to 0.011 ppt for E. coli and Listeria, respectively, at 10 log cfu/mL due to accelerated microbial growth immediately following the spike. Viscous homogenized eggs, though, impeded MNP-Salmonella migration to the magnet during separation. This phenomenon was a motivating factor in creating “dip-sticks”: plastic strips coated in MNP (MNP-strip). Rapid nano-biosensing of MNP-cell complexes in under 30 min from either suspended or strip capture was possible using electrochemical technology of spectrometry or a simple handheld potentiostat. Capture concentrates bacteria as MNP-cell from large volumes allowing strong cyclic voltammetric (CV) signaling. Normalized peak current responses (NPCR) for microbial detection from simple matrices (PBS and beef juices) showed sample (S) NPCR lower than negative controls (N) (S/N < 1.0). Whereas in complex matrices (milk, apple cider, and homogenized eggs), S/N were significantly greater than 1.0. NPCR for negative controls were found to be linearly related to matrix components fats, proteins, and sodium (R2 = 0.92). Except for E. coli in beef juices, all S/N were significant (p < 0.05) for contamination levels ranging between 6.2 to 12.3 log CFU/mL.Enhanced signaling of low pathogen presence in food was achieved using electrically active AuNP labeling. Electrochemical detection of MNP-cell-AuNP complexes with spectrophotometry or differential pulse voltammetry (DPV) was significantly more sensitive, detecting 3 log CFU/mL and 5 log CFU/mL E. coli contamination in milk (p < 0.20), respectively. Food component attachment to the complexes altered, but did not interfere, with distinguishing samples from negative controls . MNP carbohydrate ligands exposed to refrigerated milk matrix components (fats, lipids, sugars, protein and sodium) for up to 9-days still extracted bacteria. This makes possible future biocompatible tag-on nano-biosensors inside individual food packaging. Pathogen presence could be monitored over the lifetime of the product, reducing consumption of contaminated foods. Reliable frequent testing along the food supply chain would facilitate reduced human disease, while reducing industry financial losses due to foodborne outbreaks. Flexible carbohydrate-based MNP-cell/(CV) and MNP-cell-AuNP/(DPV or spectrometry) nano-biosensing with electrochemical detection can provide a truly rapid, economical test.
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Title: Some biochemical studies on seed viability
Creator: Miller, Erston V. (Erston Vinton), 1898-1985
Date: 1926
Collection: Electronic Theses & Dissertations

Title: Community detection in temporal multi-layer networks
Creator: Al-sharoa, Esraa Mustafa
Date: 2019
Collection: Electronic Theses & Dissertations
Description: "Many real world systems and relational data can be modeled as networks or graphs. With the availability of large amounts of network data, it is important to be able to reduce the network's dimensionality and extract useful information from it. A key approach to network data reduction is community detection. The objective of community detection is to summarize the network by a set of modules, where the similarity within the modules is maximized while the similarity between different modules...
Show more"Many real world systems and relational data can be modeled as networks or graphs. With the availability of large amounts of network data, it is important to be able to reduce the network's dimensionality and extract useful information from it. A key approach to network data reduction is community detection. The objective of community detection is to summarize the network by a set of modules, where the similarity within the modules is maximized while the similarity between different modules is minimized. Early work in graph based community detection methods focused on static or single layer networks. This type of networks is usually considered as an oversimplification of many real world complex systems, such as social networks where there may be different types of relationships that evolve with time. Consequently, there is a need for a meaningful representation of such complex systems. Recently, multi-layer networks have been used to model complex systems where the objects may interact through different mechanisms. However, there is limited amount of work in community detection methods for dynamic and multi-layer networks. In this thesis, we focus on detecting and tracking the community structure in dynamic and multi-layer networks. Two particular applications of interest are considered including temporal social networks and dynamic functional connectivity networks (dFCNs) of the brain. In order to detect the community structure in dynamic single-layer and multi-layer networks, we have developed methods that capture the structure of these complex networks. In Chapter 2, a low-rank + sparse estimation based evolutionary spectral clustering approach is proposed to detect and track the community structure in temporal networks. The proposed method tries to decompose the network into low-rank and sparse parts and obtain smooth cluster assignments by minimizing the subspace distance between consecutive time points, simultaneously. Effectiveness of the proposed approach is evaluated on several synthetic and real social temporal networks and compared to the existing state-of-the-art algorithms. As the method developed in Chapter 2 is limited to dynamic single-layer networks and can only take limited amount of historic information into account, a tensor-based approach is developed in Chapter 3 to detect the community structure in dynamic single-layer and multi-layer networks. The proposed framework is used to track the change points as well as identify the community structure across time and multiple subjects of dFCNs constructed from resting state functional magnetic resonance imaging (rs-fMRI) data. The dFCNs are summarized into a set of FC states that are consistent over time and subjects. The detected community structures are evaluated using a consistency measure. In Chapter 4, an information-theoretic approach is introduced to aggregate the dynamic networks and identify the time points that are topologically similar to combine them into a tensor. The community structure of the reduced network is then detected using a tensor based approach similar to the one described in Chapter 3. In Chapter 5, a temporal block spectral clustering framework is introduced to detect and track the community structure of multi-layer temporal networks. A set of intra- and inter-adjacency matrices is constructed and combined to create a set of temporal supra-adjacency matrices. In particular, both the connections between nodes of the network within a time window, i.e. intra-layer adjacency, as well as the connections between nodes across different time windows, i.e. inter-layer adjacency are taken into account. The community structure is then detected by applying spectral clustering to these supra-adjacency matrices. The proposed approach is evaluated on dFCNs constructed from rs-fMRI across time and subjects revealing dynamic connectivity patterns between the resting state networks (RSNs)."--Pages ii-iii.
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Title: Multiscale biomechanical modeling of arterial networks
Creator: Gharahi, Hamidreza
Date: 2019
Collection: Electronic Theses & Dissertations
Description: Cardiovascular diseases are the leading cause of death all around the world. With the expansion of our understanding in biomedical sciences, a variety of factors associated with the onset and progression of such diseases have been identified. In particular, mechanical stresses such as wall shear stress and circumferential stress have been proven to be primary factors for the mechanobilogy, and their homeostatic conditions are regarded as a bridge between biomechanics and cardiovascular...
Show moreCardiovascular diseases are the leading cause of death all around the world. With the expansion of our understanding in biomedical sciences, a variety of factors associated with the onset and progression of such diseases have been identified. In particular, mechanical stresses such as wall shear stress and circumferential stress have been proven to be primary factors for the mechanobilogy, and their homeostatic conditions are regarded as a bridge between biomechanics and cardiovascular biology. The study of vascular growth and remodeling (G&R) is a field that exploits computational modeling to study the changes in mechanical structure and function of blood vessels in response to altered stimuli. During the past decade, vascular G&R modeling has made significant contributions to the field of biomedical engineering through all areas of cardiovascular research. However, the previous modeling has mostly been devoted to arteries, and few studies developed vascular G&R models of the microvasculature. Additionally, other remaining tasks for the modeling include: 1) consolidation of different physical models and taking into account their interactions (e.g., fluid-solid-interactions, fluid-solid-growth) and multiscale levels in space and time and 2) realization of the modeling for the clinical practice. To this end, we developed a novel computational framework that incorporates biofluid and biosolid mechanics of arterial networks in physiological conditions and expanded it to model different vascular adaptation processes. This framework integrated essential features from a constrained mixture model of G&R and blood circulation with an extension of Murray's law to construct a spatially multiscale vascular tree. We formulated the framework as a cost optimization problem where the design of the vasculature was governed by minimization of the metabolic dissipation under mechanical equilibrium as a constraint. Subsequently, we presented two implementations of the model to study two multiscale problems: pulmonary arterial hypertension (PAH) and coronary flow regulation. In the case of PAH, we used the framework to estimate the homeostatic characteristics of the arterial tree as well as their hemodynamics. The results showed good agreement with the available experimental data in the pulmonary arterial vasculature. Furthermore, we used Womersley's analytical solution combined with the theory of small-on-large in finite elasticity to simulate the pulsatile hemodynamics in the pulmonary arterial tree. This study lays the groundwork for further temporally multiscale studies of PAH where long-term G&R in the vasculature (days to weeks) are coupled with short-term hemodynamics (cardiac cycle) in a fluid-solid-growth modeling (FSG) framework. In the case of coronary network, the baseline properties of two myocardial arterial trees distal to left anterior descending coronary artery were established using the presented method. Consequently, three different coronary flow regulation mechanisms (flow-induced, myogenic, and metabolic) were implemented using the constrained mixture models of small arteries and arterioles. The model was then calibrated against the experimental autoregulatory pressure-flow relations. Moreover, the prediction capability of the model was evaluated by simulations of exogenous adenosine infusion and inhibition of nitric oxide synthesis. In closing, the developed framework exhibited great promise for applications in the study of vascular adaptations in physiological and pathophysiological conditions. Particularly, after the homeostatic baseline of an arterial tree is established, the kinetics of production and removal of constituents from stress-mediated G&R models can be used to simulate the short- and long-term evolution of vascular tissues in disease conditions. Furthermore, this research will set the cornerstone for much needed in-silico experiments on palliative or curative managements of vascular diseases.
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Title: Evaluation of riparian community capitals and their relationship to adaptive lake management outcomes
Creator: Jermalowicz-Jones, Jennifer L.
Date: 2017
Collection: Electronic Theses & Dissertations
Description: While inland lakes in Michigan provide multiple community benefits, the aquatic ecosystems in many of these lakes are now significantly degraded, resulting in damages to ecological integrity, decreased utility by citizens and a decline in the municipal tax base due to loss in property values. Lake communities vary significantly in their capacity to identify problems and implement programs to improve lake water quality over time. This study utilizes the Community Capitals Framework (CCF) to...
Show moreWhile inland lakes in Michigan provide multiple community benefits, the aquatic ecosystems in many of these lakes are now significantly degraded, resulting in damages to ecological integrity, decreased utility by citizens and a decline in the municipal tax base due to loss in property values. Lake communities vary significantly in their capacity to identify problems and implement programs to improve lake water quality over time. This study utilizes the Community Capitals Framework (CCF) to investigate what community capitals (assets) lead to better capacity and outcomes in terms of improved management of lake resources through implementation of Best Management Practices (BMPs). It also evaluates the Trophic State Index (TSI) of the lakes relative to the various community capitals. The exploration of this approach may be used in the future to specify which assets are most needed for improving water quality. This research increases our ability to understand capital resources and ultimately make recommendations to individual communities for optimal management capacity. Statistically significant findings include a positive correlation between cultural capital and BMPs in riparian communities with active Lake Management Plans (LMPs) demonstrating that as cultural capital increased, communities were more likely to implement BMPs. Additionally, there were significant differences between BMPs and financial capital for the riparian communities. Communities with higher financial capital that had LMP's were more likely to also implement BMPs. Lastly, there were significant differences between human capital and BMPs for the LMP communities, indicating that higher human capital was associated with a greater ability to implement BMPs.
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Title: Precision measurement of the Beta-energy spectrum in 2076He decay
Creator: Huyan, Xueying
Date: 2019
Collection: Electronic Theses & Dissertations
Description: Precision measurements of the β-energy spectrum in nuclear and neutron decays have a great potential to find possible signatures of new physics beyond the standard electroweak model. Such signatures would produce a distortion to the β-energy spectrum relative to the Standard Model prediction. In Gamow-Teller transitions, these distortions would indicate the presence of the exotic tensor type interactions. An interesting candidate for this study is 6He because the simplicity of its decay and...
Show morePrecision measurements of the β-energy spectrum in nuclear and neutron decays have a great potential to find possible signatures of new physics beyond the standard electroweak model. Such signatures would produce a distortion to the β-energy spectrum relative to the Standard Model prediction. In Gamow-Teller transitions, these distortions would indicate the presence of the exotic tensor type interactions. An interesting candidate for this study is 6He because the simplicity of its decay and other nuclear properties allow an accurate theoretical description of the spectral shape.At the National Superconducting Cyclotron Laboratory we have used a calorimetric technique for measuring the shape of the β-energy spectrum in 6He decay. The radioactive ions were implanted into the active volume of a detector; this eliminates the critical instrumental effect related to the backscattering of β particles. The goals of the experiment are to provide the first measurement of the weak magnetism form factor (bWM) in 6He decay and the first direct measurement of the Fierz interference term (bGT) in Gamow-Teller decay.This work summarizes the efforts on this experiment, focusing on the data analysis of the main systematic effects as well as the projected sensitivities to the observables. The estimates of bWM and bGT are bWM = ? ± 4.9stat ± 11sys and bGT = (? ± 3.1stat ± 4.7sys) × 10−3, where the central values of bWM and bGT will be determined in the future analysis. The predicted uncertainty of bGT satisfies the precision goal of O(10−3), a level which allows new constraints on tensor couplings beyond the Standard Model.
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Title: A finite element study of human thigh area in seated posture for pressure ulcer prediction and prevention
Creator: Chen, Sheng
Date: 2019
Collection: Electronic Theses & Dissertations
Description: Pressure ulcers (PUs), also known as pressure sores, are localized damage to the skin and underlying tissues, usually occurring over a bony prominence and caused by sitting or lying in one position for long time. PUs are a detriment to the well-being of people who lose their mobility either permanently or temporarily, and high morbidity and mortality are associated with PUs. Although the initiating mechanism of PUs is still unclear, it is commonly accepted that internal normal and shear...
Show morePressure ulcers (PUs), also known as pressure sores, are localized damage to the skin and underlying tissues, usually occurring over a bony prominence and caused by sitting or lying in one position for long time. PUs are a detriment to the well-being of people who lose their mobility either permanently or temporarily, and high morbidity and mortality are associated with PUs. Although the initiating mechanism of PUs is still unclear, it is commonly accepted that internal normal and shear stresses, due to the presence of unrelieved external loads, play a central role in the formation and development of these wounds. Despite the significance of internal stresses in PUs formation, interfacial pressures, which are a surface measure of stress, are the indicators commonly used to develop practices and protocols to minimize loading on the soft tissue. However, no direct correlation exists between interfacial pressure and internal stresses of soft tissue. Therefore, tools and methods that can show internal distributions of soft tissue's stresses and strains as a response to external loading are needed.The ability of finite element (FE) models to accurately represent the anatomical structure of the leg and buttocks area and to estimate the localized stress/strain fields within highly deformable media, makes them powerful tools to investigate soft tissue response to external loadings. Despite the significant advancement previous studies have achieved, there are still important aspects in human thigh-buttock soft tissue modeling area that need to be improved. Two challenges are identified in this dissertation: 1) Microstructurally motivated skin modeling for an individual skin layer in finite element model. 2) Parameters estimation associated with large deformations.To address the first challenge, a microstructurally based constitutive model is proposed to describe the mechanical behavior of skin. The constitutive model incorporated the distribution of collagen fiber bundle orientations and relative collagen content measured from histology, and shows good agreement with the tensile test data.To address the second challenge, an optimization procedure that is able to match nonlinear behaviors between FE simulation and in vivo experimental data is developed. The difference between 3D and semi-3D model is quantified, and the accuracy of four commonly used constitutive model representing soft tissue nonlinear mechanical behavior is compared.Finally, a thigh FE model that has detailed anatomical representation of different soft tissue types, i.e., skin, fat, and muscle, is developed. The subject-specific in vivo experimental data are used to inform the optimization procedure to obtain best-fit constitutive parameters for different soft tissue types. The research in this dissertation provides an approach to describe the in vivo mechanical behavior of soft tissues in thigh-buttock area accurately through FE modeling. The constitutive parameters informed by in vivo data in this dissertation are valuable to facilitate future FE modeling studies to achieve accurate internal stress/strain distribution of soft tissues in thigh-buttock area.
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Title: Wishi stories : rhetorical strategies of survivance and continuance in Oklahoma Cherokee foodways
Creator: Shade-Johnson, Jaquetta
Date: 2018
Collection: Electronic Theses & Dissertations
Description: The author employs a description of the Cherokee practices of foraging and cooking wishi (hen-of-the-woods mushrooms), a Cherokee delicacy, to argue that American Indians use foodways to survive and resist the ongoing project of settler colonialism, and to carry culture forward for future generations. Using a cultural rhetorics methodology of story, she gathered the oral histories of three tradition-bearers from her own tribal community who shared with her their experiences of foraging and...
Show moreThe author employs a description of the Cherokee practices of foraging and cooking wishi (hen-of-the-woods mushrooms), a Cherokee delicacy, to argue that American Indians use foodways to survive and resist the ongoing project of settler colonialism, and to carry culture forward for future generations. Using a cultural rhetorics methodology of story, she gathered the oral histories of three tradition-bearers from her own tribal community who shared with her their experiences of foraging and cooking wishi.
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Title: Addition and removal energies via the in-medium similarity renormalization group method
Creator: Yuan, Fei (Software engineer)
Date: 2018
Collection: Electronic Theses & Dissertations
Description: "The in-medium similarity renormalization group (IM-SRG) is an ab initio many-body method suitable for systems with moderate numbers of particles due to its polynomial scaling in computational cost. The formalism is highly flexible and admits a variety of modifications that extend its utility beyond the original goal of computing ground state energies of closed-shell systems. In this work, we present an extension of IM-SRG through quasidegenerate perturbation theory (QDPT) to compute...
Show more"The in-medium similarity renormalization group (IM-SRG) is an ab initio many-body method suitable for systems with moderate numbers of particles due to its polynomial scaling in computational cost. The formalism is highly flexible and admits a variety of modifications that extend its utility beyond the original goal of computing ground state energies of closed-shell systems. In this work, we present an extension of IM-SRG through quasidegenerate perturbation theory (QDPT) to compute addition and removal energies (single particle energies) near the Fermi level at low computational cost. This expands the range of systems that can be studied from closed-shell ones to nearby systems that differ by one particle. The method is applied to circular quantum dot systems and nuclei, and compared against other methods including equations-of-motion (EOM) IM-SRG and EOM coupled-cluster (CC) theory. The results are in good agreement for most cases. As part of this work, we present an open-source implementation of our flexible and easy-to-use J-scheme framework as well as the HF, IM-SRG, and QDPT codes built upon this framework. We include an overview of the overall structure, the implementation details, and strategies for maintaining high code quality and efficiency. Lastly, we also present a graphical application for manipulation of angular momentum coupling coefficients through a diagrammatic notation for angular momenta (Jucys diagrams). The tool enables rapid derivations of equations involving angular momentum coupling - such as in J-scheme - and significantly reduces the risk of human errors."--Page ii.
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Title: The role of oxytocin receptors in the dorsomedial tegmentum in postpartum socioemotional behaviors
Creator: Grieb, Zachary Adam
Date: 2018
Collection: Electronic Theses & Dissertations
Description: Oxytocin signaling is well known to positively influence maternal caregiving behaviors. Therefore, oxytocin receptor (OTR) expression has been characterized in many sites of the brain across female reproductive states. However, almost all characterization of OTRs across reproduction has focused on forebrain sites, even though there are known OTRs in the midbrain dorsal raphe (DR) and periaqueductal gray (PAG) (i.e., the dorsomedial tegmentum). Ignoring these sites is surprising, given that...
Show moreOxytocin signaling is well known to positively influence maternal caregiving behaviors. Therefore, oxytocin receptor (OTR) expression has been characterized in many sites of the brain across female reproductive states. However, almost all characterization of OTRs across reproduction has focused on forebrain sites, even though there are known OTRs in the midbrain dorsal raphe (DR) and periaqueductal gray (PAG) (i.e., the dorsomedial tegmentum). Ignoring these sites is surprising, given that these sites are part of the neurobiological network underlying postpartum behaviors (see background review in Chapter One). To begin to understand the role of OTRs in the dorsomedial tegmentum on postpartum behavior, the experiments in Chapter Two of this dissertation measured autoradiographic binding of the selective OTR antagonist, d(CH2)5–8-ornithine-vasotocin, across four different female reproductive states, diestrous virgins (DV), pregnancy day 10, day of parturition, and postpartum day 7 (PPD 7). OTR binding in the rostral DR and the lateral PAG were higher in recently-parturient dams compared to DV females, but these levels were returned to DV levels by PPD 7. Additionally, there was increased oxytocin-immunoreactive (ir) fiber length in the DR and PAGvl in PPD 7 dams compared to either DV or recently-parturient dams. Given the heterogenous populations of cells in the DR, expression of OTRs on three of the most abundant neuronal phenotypes in the DR, serotonin, dopamine, and GABA, were analyzed in groups of DV and recently-parturient dams. There were more dopaminergic and serotonergic neurons containing OTR immunoreactivity in the rostral DR of recently- parturient dams compared to DV, whereas the number of glutamic acid decarboxylase-OTR colocalized cells was lower in the rostral DR of recently-parturient dams compared to DV. Overall, these data suggest that specific regions of the midbrain PAG are more sensitive to oxytocin signaling around parturition, with dopaminergic and serotonergic neurons accounting for some of that increased sensitivity. Given these changes in dorsomedial tegmentum OTR expression across the early postpartum period, their potential role in postpartum socioemotional behaviors was directly examined. An adeno-associated virus promoting the expression of shRNA against OTR mRNA was created to establish a long-term knock down of OTR expression in the dorsomedial tegmentum (Chapter Three). On pregnancy day 8, females received site-specific infusion of either OTR shRNA vector or a scrambled control vector. Following parturition, dams’ socioemotional behaviors (i.e. caregiving, aggressive, anxiety-like, and depressive-like behaviors) were observed. OTR knockdown (OTRKD) in the dorsomedial tegmentum lead to higher rates of infanticide, less kyphotic nursing (i.e., nursing in an upright erect posture), and more non-pup directed behaviors. There were no effects of OTRKD on dams’ retrieval performance. OTRKD in the dorsomedial tegmentum also increased postpartum aggression, decreased postpartum anxiety, and increased depressive-like behaviors. Finally, OTRKD in the dorsomedial tegmentum decreased serotonin-ir fiber length in the primary somatosensory cortex (S1). Overall, OTR expression in the dorsomedial tegmentum is sensitive to female reproductive state and modifies numerous postpartum behaviors. It may do so by affecting the S1 plasticity necessary to optimize maternal tactile sensitivity to offspring (discussed in Chapter Four).
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Title: Lost or found : experiences of first-year Chinese international students who are on academic probation after their first semester
Creator: Mei, Jianyang
Date: 2019
Collection: Electronic Theses & Dissertations
Description: In recent years, the number of Chinese international undergraduate students sharply increased in higher education institutions in the U.S. Meanwhile, this student population experiences challenges in their transition in U.S. colleges, and academic probation is one challenge that Chinese international undergraduate students have. Being on academic probation has negative impacts on students' persistence and retention rates and 4,5,6-year graduation rates, and the increasing number and...
Show moreIn recent years, the number of Chinese international undergraduate students sharply increased in higher education institutions in the U.S. Meanwhile, this student population experiences challenges in their transition in U.S. colleges, and academic probation is one challenge that Chinese international undergraduate students have. Being on academic probation has negative impacts on students' persistence and retention rates and 4,5,6-year graduation rates, and the increasing number and percentage of Chinese international students also bring challenges to U.S. higher education institutions. To explore the reasons for being on academic probation of Chinese international undergraduate students, this research studied the experiences of the first-year Chinese international undergraduate students who are on academic probation after their first semester in a Research I public university. This mix-method study collected data of students' educational records, survey, and interview, in order to explore the trends among first-year Chinese international undergraduate students who are on academic probation after their first semester, the correlations between their TOEFL, SAT, ACT scores and first semester GPAs, their academic performance in each course they enrolled in their first semester, and how those students perceived and made sense of being on academic probation. The data analysis demonstrated that the most reasons for being on academic probation after their first semester are in socio-emotional engagement, not in academic proficiency. The top 2 main reasons for being on academic probation identified by interviewees are not taking their study seriously and not studying (hard). Different from many studies about (Chinese) international students, the language barrier was not identified as one top reason for being on academic probation by survey respondents and interviewees. The main finding of this study is the goal of participants was to get an admission letter from a U.S. college. Participants actually only prepared for the study abroad tests, such as TOEFL, SAT, and ACT, and did not prepare for knowledge, skills, and abilities that are essential to survive and thrive in the academic learning at U.S. colleges. This study also found being on academic probation is actually an issue caused by the study abroad craze that driven by policy and capital, and it needs the effort and input from Chinese international students, Chinese parents, and U.S. higher education institutions in order to solve this problem. Therefore, this study provided recommendations to Chinese international students and Chinese parents, as well as faculty, staff, and administrators in U.S. colleges at the individual level, institutional level, and policy level, in order to support the academic learning and transition of Chinese international undergraduate students.
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Title: Social relationships and progression of frailty : exploring the reciprocal association of social ties and physical vulnerability in later life
Creator: Lee, Ji Hyun (Graduate of Michigan State University)
Date: 2019
Collection: Electronic Theses & Dissertations
Description: Frailty is described as a state of heightened vulnerability and functional impairment due to the cumulative declines across multiple physiological systems. When faced with stressor events, older adults with frailty are in higher risk of adverse health outcomes. While the prevalence of frailty generally increases with age, there are considerable heterogeneity in onset and progression of frailty among older population. Growing attention is given to identifying the psychosocial factors related...
Show moreFrailty is described as a state of heightened vulnerability and functional impairment due to the cumulative declines across multiple physiological systems. When faced with stressor events, older adults with frailty are in higher risk of adverse health outcomes. While the prevalence of frailty generally increases with age, there are considerable heterogeneity in onset and progression of frailty among older population. Growing attention is given to identifying the psychosocial factors related to the development of frailty. Social relationships often serve as a vital context of health, where older adults experience multidimensional and dynamic exchange with close others as they age. In this dissertation, two studies are conducted to investigate complex and reciprocal nature of social relationships and frailty progression in older adulthood. The data are from the six waves (2006-2016) of the Health and Retirement Study (HRS), a nationally representative study of older adults in U.S. aged 50 and older. The first study utilized the convoy model of social relations to provide comprehensive investigation of how different aspects of social relations are associated with frailty progression over a decade. There were three distinctive subpopulations following a different frailty progression trajectory. When social network and relational quality with spouse, children, family, and friends were examined, higher frequency of contact with friends were associated with lesser frailty. Negative relationship quality with social ties were detrimental to frailty progression, such that strain with spouse and kin (children and extended family) had an additive effect on belonging to high frailty or steep increase frailty trajectory groups. The perceived loneliness partially explained the negative effect of spousal strain, but the negative effect of large family size and strain with kin were independent from loneliness. The second study explored the health contexts of older couple's marital quality, specifically focusing on the presence of frailty and depression within- and across-person in the marital relationship. Using three waves of dyadic data from HRS, I found that one's own and partner's higher frailty and higher depression all had independent associations with one's higher marital strain. For one's marital support, one's own higher frailty, higher depression, and partner's higher depression had negative effects. There was an across-person interaction effect of frailty, such that one's marital quality was affected by their partner's higher level of frailty only when their own health was good. Having a husband with higher frailty was associated with higher marital strain for wives. Most effects were stable over time. Overall, the findings illustrate the significance of social relationship context as a predictor for different trajectory of frailty progression. The size, frequency of contact, positive, and negative quality were linked to frailty differentially by relationship type, underscoring the benefits of comprehensive examination of social experiences. Further, the level of frailty and depression were linked to perceived marital quality of both members of the couple, especially in damaging manner when healthier spouse is faced with partner's health problems. Taken together, my dissertation demonstrated the importance of studying linked lives in context of health conditions prevalent in older adulthood. The findings can be useful to practitioners and policy makers in understanding the intricate link between social relations and frailty as well as in identifying modifiable factors for frailty prevention.
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Title: Structural and functional remodeling of neuronal circuitry surrounding implanted electrodes
Creator: Salatino, Joseph William
Date: 2019
Collection: Electronic Theses & Dissertations
Description: Microelectrode arrays designed to map and modulate neuronal circuitry have enabled greater understanding and treatment of neurological injury and disease. However, poor biological integration remains a significant barrier to the longevity and stability of electrodes implanted in the brain, where gliosis and neuronal loss are commonly attributed to instability and loss of signal over time. However, these metrics do not reliably predict signal loss, and device failure modes remain elusive. Here...
Show moreMicroelectrode arrays designed to map and modulate neuronal circuitry have enabled greater understanding and treatment of neurological injury and disease. However, poor biological integration remains a significant barrier to the longevity and stability of electrodes implanted in the brain, where gliosis and neuronal loss are commonly attributed to instability and loss of signal over time. However, these metrics do not reliably predict signal loss, and device failure modes remain elusive. Here, this work provides fundamental insight into biological mechanisms that contribute to these failure modes, as well as develops genetic engineering strategies to improve the biointegration of brain implants.While signal-generating neurons have traditionally been considered the important target cells for implanted electrodes, it has become increasingly appreciated that glia remodel the structure and function of neuronal networks following injury, where recent work has uncovered mechanisms relevant to the injuries and ensuing gliosis caused by the implantation of chronic devices. Chapter 2 disseminates important considerations for glial reactivity on device performance and provides a framework for topics explored in subsequent Chapters. Although decades of work has demonstrated that cortical injury generates long-term remodeling of excitatory/inhibitory synapses (the connections which facilitate the propagation of information between neurons) and ion channels (the transmembrane proteins responsible for generating neuronal signals), these mechanisms have not been investigated around implanted arrays; however, the consequences of these events hold significant implications for the long-term recording stability of implanted devices. Chapter 3 reveals novel changes in both excitatory and inhibitory synaptic circuitry surrounding implanted microelectrodes, where early elevations in excitatory synapses are followed by a shift to inhibitory tone in the chronic setting. A novel subtype of glia is also identified local to the device interface. Chapter 4 reveals a novel relationship between electrophysiological recordings and ion channel expression surrounding implanted arrays over time, where a loss of sodium channel expression and gain in potassium channel expression corresponds with a loss of recorded signals over time. Together, this work supports a trend from hyper- to hypo-excitability, which temporally coincides with signal variability and loss observed with chronic devices.The previous chapters provide fundamental insight into major circuit changes at the interface that inform both basic-science knowledge and new strategies for improving the biointegration of brain implants. We are developing new approaches to reveal the mechanistic role of these factors in affecting recorded signals over time. Chapter 5 covers ongoing work that includes the development and validation of innovative strategies to deliver genetic material at the interface in vivo to yield entirely new avenues of research with opportunities to regulate gene expression and/or introduce new genetic material to rewire the interfacial network. Future directions are discussed with opportunities to unmask key circuit-remodeling effects that impair device performance as well as inform the seamless integration of brain implants.
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Title: Optical transmission scanning and hybrid acousto-optical techniques for NDE and SHM of structural composites
Creator: Karpenko, Oleksii
Date: 2018
Collection: Electronic Theses & Dissertations
Description: Fiber reinforced polymer (FRP) composites have been extensively used in aerospace, marine and defense industries due to the many advantages they offer including light-weight, corrosion resistance and excellent thermo-mechanical properties. Increasing fuel-efficiency demands and reducing green-house emissions has also propelled the use of FRP composites in the automotive industry. However, despite excellent mechanical properties of FRPs, their anisotropy, brittle nature and the vulnerability...
Show moreFiber reinforced polymer (FRP) composites have been extensively used in aerospace, marine and defense industries due to the many advantages they offer including light-weight, corrosion resistance and excellent thermo-mechanical properties. Increasing fuel-efficiency demands and reducing green-house emissions has also propelled the use of FRP composites in the automotive industry. However, despite excellent mechanical properties of FRPs, their anisotropy, brittle nature and the vulnerability to flaws during fabrication and service has propelled the need of nondestructive evaluation (NDE) and structural health monitoring (SHM) techniques. This dissertationpresents three major contributions to the fields of NDE and SHM of structural composites:• optical transmission scanning (OTS) for rapid, non-contact and quantitative NDE of glass and aramid FRPs;• optical frequency-domain reflectometry (OFDR) for distributed monitoring of strains in FRPs using single-mode (SM) optical fibers and Rayleigh back-scattering;• hybrid acousto-optic health monitoring of FRPs using guided waves (GW) and Fabry-Perot interferometric sensors based on chirped fiber Bragg-gratings (CFBG-FPI).Chapter I presents an OTS system for quantitative NDE of GFRP samples. The technique provides high-resolution, rapid, and non-contact optical transmittance scans. Experimental implementation of the technique and advanced data analysis protocol developed for impact damage evaluation are presented. Obtained experimental results show that other defects and certain microstructural variations in GFRP composites can be easily identified by OTS, because the technique is sensitive to localized changes of optical properties such as radiation absorption and scattering. The applications of OTS are extended to GFRP plates with improperly mixed resin, inclusions, and delaminations. Finally, the capabilities of the technique to evaluate the distribution of adhesive and detect fatigue damage in adhesively bonded GFRP joints are demonstrated.Chapter II describes the development of advanced signal processing algorithms for strain sensing in optical fibers using Rayleigh back-scattering and the OFDR technique. Distributed displacement and strain sensing along the fiber length is implemented using the OFDR-1000 system from General Photonics Corporation (Chino, CA). Performance of the system is validated by measuring strains introduced in the optical fiber by the piezoelectric fiber stretcher. Chapter III lays out the approach for diagnostic imaging of plate-like structures using hybrid acousto-optic technique. Guided waves are excited with surface-bonded piezoelectric wafers and are sensed with pairs of chirped fiber Bragg-gratings that form Fabry-Perot interferometers inside the surface-bonded optical fiber. Initial experimental results obtained on aluminum plates demonstrate that CFBG-FPIs are sensitive to both symmetric and antisymmetric fundamental GW modes. Structural damage is successfully located using Delay-and-Sum (DAS) imaging.
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Title: The life and death of bone : a regional approach to the interpretation of fragmented and culturally modified Oneota human remains
Creator: Geske, Nicole Lynne
Date: 2018
Collection: Electronic Theses & Dissertations
Description: This dissertation utilizes previously collected archaeological, mortuary, and osteological data from multiple village and mortuary sites attributed to the Midwest archaeological culture known as Oneota (AD 900-1700). Isolated and fragmented human remains are commonly encountered in both mortuary and non-mortuary contexts, including burials, refuse and storage pits, and scattered throughout villages and middens. Many of these remains are also culturally modified through processes such as...
Show moreThis dissertation utilizes previously collected archaeological, mortuary, and osteological data from multiple village and mortuary sites attributed to the Midwest archaeological culture known as Oneota (AD 900-1700). Isolated and fragmented human remains are commonly encountered in both mortuary and non-mortuary contexts, including burials, refuse and storage pits, and scattered throughout villages and middens. Many of these remains are also culturally modified through processes such as burning, incising, and polishing. Although research regarding these remains is limited, these deposits have been attributed to violence and/or trophies of war. Therefore, the primary objective of this research was to examine the presence of fragmented and culturally modified human remains at Oneota sites and to theorize their possible meaning(s). This also included an evaluation of previous conclusions of violence. A secondary objective of this dissertation was to assess if published and previously collected data could be used to answer new research questions. Using spatial and correspondence analyses, this dissertation demonstrates patterning in the presence and location of culturally modified human remains. A contextual approach, as well as a theoretical framework that views the body as dividual and partible, were also used to demonstrate how human remains can become fragmented and isolated. Finally, ethnographies of the Winnebago (Ho-Chunk) and Ioway were used to find historical links between past and historic practices. This dissertation demonstrates a preference for cranial and long bone elements for fragmentation, as well as cultural modification. The choice of cranial elements is tied to the concept of the location of the soul, while the act of cultural modification is a transformation to either enhance or erase previously identities. Due to the degree of fragmentation, it cannot be precisely determined who specifically was used for this treatment. It is argued that these remains represent an aspect of the Oneota mortuary program that has not regularly been included in previous analyses.Multiple difficulties in data collection and analysis were encountered, primarily for data regarding fragmented and isolated human remains. Several varying treatments for isolated human remains were noted, leading to difficulty in their analysis and interpretation. Due to this difficulty, suggestions for future data collection for isolated human remains are provided.
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Title: CONSUMER RESPONSES TO INTENSE NEGATIVE EMOTION IN ELECTRONIC WORD-OF-MOUTH : THE ROLE OF TIE-STRENGTH AND DIAGNOSTIC CUES
Creator: Kim, Wonkyung
Date: 2018
Collection: Electronic Theses & Dissertations
Description: Social media have become widely used platforms for dissatisfied customers to express disappointment with failed goods and services. Referred to as an online “firestorm,” negative eWOM spreads instantly and exponentially through people’s social networks (Pfeffer, Zorbach, & Carley, 2014). Marketers may worry that strong emotional expression of a complaint would lead to negative brand consequences, but that is an empirical question. Guided by Attribution theory and Accessibility-Diagnosticity...
Show moreSocial media have become widely used platforms for dissatisfied customers to express disappointment with failed goods and services. Referred to as an online “firestorm,” negative eWOM spreads instantly and exponentially through people’s social networks (Pfeffer, Zorbach, & Carley, 2014). Marketers may worry that strong emotional expression of a complaint would lead to negative brand consequences, but that is an empirical question. Guided by Attribution theory and Accessibility-Diagnosticity model, this study examined how tie-strength and diagnostic information influence consumers’ inference-making of intense negative eWOM sender motives which in turn leads to credibility perceptions. An online experiment manipulated tie strength and the behavioral patterns of diagnostic cues to address the as yet unstudied effects of negative eWOM on credibility perception, attitude toward the brand, and sharing intention.This study used a 3 (Tie-strength: strong vs. weak vs. none) x 4 (Cues Present [high consistency/ medium consistency/ low consistency], Not Present) between-subjects, posttest only random assignment factorial experimental design. The results showed that the consistency of behavioral pattern manifested in previous posts of the eWOM sender influences attribution of sender’s motives. That is, when the original negative eWOM and the previous posts show consistently high consistency (i.e., negative valence posts), receivers made more dispositional attributions compared to when the previous posts showed low consistency (i.e., positive valence posts). Such impact of the previous posts was moderated by the tie-strength between the sender and the receiver. When the source is a close friend, receivers did not consider the cues of past behavioral pattern, unlike receivers who viewed a post from an acquaintance or a stranger as a sender of intense negative eWOM. Furthermore, indirect effects suggest that attribution of sender motives further influences persuasive outcomes such as brand attitude and sharing intention. The results give some implications for brand managers and eWOM platform developers. First, those who manage social media consumer complaints should consider the network of eWOM senders. Second, eWOM platforms should consider ways to highlight diagnostic cues such as previous posts. Previous posts can be emphasized by showing the previous rating history of the reviewer. In this way, receivers would not necessarily visit the eWOM sender’s profile page to gather more information on previous eWOM behaviors.
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Title: Learning algorithms for detecting disinformation on social media
Creator: VanDam, Courtland
Date: 2019
Collection: Electronic Theses & Dissertations
Description: Social media has become a widely accessible medium for users to share their opinions and details of their personal lives, including first hand accounts of emerging/disaster events, to a wide audience. However malicious entities may abuse users' trust to disseminate disinformation, i.e. false and misleading information. The disinformation disseminated on social media can have a significant impact offline. For example, fake news is suspected to have influenced the 2016 U.S. political election....
Show moreSocial media has become a widely accessible medium for users to share their opinions and details of their personal lives, including first hand accounts of emerging/disaster events, to a wide audience. However malicious entities may abuse users' trust to disseminate disinformation, i.e. false and misleading information. The disinformation disseminated on social media can have a significant impact offline. For example, fake news is suspected to have influenced the 2016 U.S. political election. Rumors on social media can mislead criminal investigations, e.g. the investigation of the 2013 Boston Bombing. To mitigate such impacts, automated detection of social media disinformation is thus an important research problem. This dissertation proposes algorithms to detect two approaches hackers use to disseminate disinformation-hashtag hijacking and compromising accounts. Hashtags are terms added to social media posts that are used to provide context to the posts, so those seeking to learn more about a given topic or event can search for posts containing related hashtags. However critics and attention-seeking trolls can mislead the public via hashtag hijacking. Hashtag hijacking occurs when one group of users takes control of a hashtag by using it in a different context than what was intended upon creation. Anyone can participate in hashtag hijacking, but to be successful, a coordinated effort among several accounts posting that hashtag is needed. This dissertation proposes HASHTECT, an unsupervised learning framework that uses a multi-modal nonnegative matrix factorization method for detecting hijacked hashtags. Experimental results on a large-scale Twitter data showed that HASHTECT is capable of detecting more hijacked hashtags than previously proposed algorithms. Another approach for disseminating disinformation is by compromising users' accounts. A social media account is compromised when it is accessed by a third party, i.e. hacker, without the genuine user's knowledge. Compromised accounts are damaging to the account holder as well as the accounts audience, e.g. followers. Hackers can damage the user's reputation, e.g. by posting hateful rhetoric. They also disseminate misleading information including rumors and malicious websites, e.g. phishing or malware. In this dissertation, I propose two compromised account detection algorithms, CADET and CAUTE. CADET is an unsupervised multi-view learning framework that employs nonlinear autoencoders to learn the feature embedding from multiple views. The rationale behind this approach is that an anomalous behavior observed in one view, e.g. abnormal time of day, may not indicate a compromised account. By aggregating the data from multiple views, CADET projects the features from all the views into a common lower-rank feature representation and detects compromised accounts in the shared subspace. On the other hand, CAUTE focuses on detecting compromised accounts early, by detecting the compromised posts. Given a user-post pair, CAUTE is a deep learning framework which simultaneously learns the encodings for the user as well as the post to detect whether the post was compromised, i.e. was written by a different user. By training a neural network on the residuals from the post and user encodings, CAUTE can classify whether a post is compromised with higher accuracy than several existing compromised account detection algorithms.
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