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Essays on Momentum and Its Sources of Abnormal Returns
No full textIn the first chapter, I investigate the effects of private information in determining price momentum, as measured by the probability of informed trading (PIN). Leveraging recent advances in PIN measure construction, I document that the momentum effect is most pronounced among stocks with substantial private information, highlighting the importance of informed trading in driving the strategy returns. Controlling various firm and stock characteristics, the private information channel emerges as a strong and independent effect influencing momentum profits. Additionally, the study finds that momentum stemming from limited investor attention paid to market prices works well only among stocks with substantial private news (high PIN). Stocks with low PIN do not exhibit any such return continuations, even when investor inattention is high.
The second chapter examines the momentum spillover strategy from the US equity to corporate bond market, i.e., whether corporate bonds ranked on corresponding issuer’s past stock returns exhibit momentum. I conclude that the six-month ranking and holding period momentum strategy does not yield any significant premium, presenting an unsuccessful out-of-sample test of Gebhardt et al. (2005). However, it documents highly positive and significant short-term momentum spillover profits with annualized returns of 8-9\%. This effect is robust across investment-grade and high-yield bonds, with higher and more persistent returns in the latter. The results are robust to credit risk, liquidity, and investor attention controls. Overall, the evidence implies a weak presence of return continuation anomaly in the corporate bond market, thus, making it an outlier in momentum literature.
In the third chapter, I attempt to understand the relative importance of tangible (past accounting measure-based fundamental performance) and intangible (constituent of past returns orthogonal to prior fundamental performance) information in explaining price momentum returns, following Daniel and Titman’s (2006) return decomposition methodology. The study finds weak evidence of any relation between future returns and the tangible component; however, it establishes a strong and positive connection between the intangible constituent and momentum strategy returns. It suggests that investors underreact more significantly to relatively abstract information regarding a firm’s past performance. This seems to be consistent with behavioral explanations proposed in the literature
Design and Investigation of Quadratic Cross Fractal Electromagnetic Bandgap Structures for Suppression of Surface Waves
No full textWithin a microstrip antenna array with a shared ground plane, surface waves will induce
unwanted mutual coupling across the array elements. These surface waves propagate along
the boundary between the air-dielectric interface due to total internal reflection and the
dielectric-conductor interface due to surface currents. The effects of surface waves are
exacerbated by increasing thickness of the substrate as well as by increasing the value of
the relative dielectric constant of the substrate material. Electromagnetic bandgap (EBG)
structures introduce a high-impedance surface when incorporated into the dielectric,
inhibiting surface wave propagation over a selected frequency range. The EBG surface can
be created through the use of periodic structures which cause a varying reflection phase.
As a consequence, the EBG surface creates pass bands and stop bands.
Due to EBG structures having a dependency upon periodicity, fractal structures have been
studied for their improvements upon traditional “mushroom-like” or "pad and via"
(PV)EBG structures due to their inherent self-similarity. In this thesis, the use of a
quadratic cross as a novel PVEBG is investigated. The quadratic cross fractal is a variant
of the Koch curve. To generate the curve, a three-segment generator unit is reduced by a
scaling factor, then three scaled units are added to the generator, one scaled unit to each
original segment. Finally, one-half of a scaled segment (an edge of the scaled unit) is added
to each leg of the generator. To characterize this PVEBG structure, an approximate
lumped-circuit model is derived and compared against simulations of the PVEBG structure
using Altair FEKO. This novel PVEBG is investigated by comparing the performance of the quadratic cross structure to the canonical square patch PVEBG structure in a 1x2
microstrip antenna array configuration. Peripheral effect measurements of gain, bandwidth,
and resonant frequency are also described. Marginal improvement in gain and bandwidth is
seen over the square patch at second and third order iterations, but the surface wave
suppression is not notably improved
THE REPRESENTATIONS OF VISUAL WORKING MEMORY: WHERE, WHAT, AND HOW
No full textVisual working memory allows humans to remember things that they saw a few moments ago and that memory can last for a short period of time and it is an essential function for a lot of cognitive processes. This dissertation focuses on three basic questions regarding visual working memory. Specifically, where is visual working memory (not) maintained in the human brain? In what format is it represented? And how information exerts its influence on the memory capacity?
Firstly, I investigated visual working memory performances under visual interferences, across a variety of stimuli categories. Once consolidated, visual working memories are intact even in face of drastic disruptions, in huge contrast with performances of iconic memory, which is known to rely on sensory regions. The contrast suggests that visual working memory is unlikely to be maintained in the early visual areas as the sensory recruitment theory of visual working memory claims. Instead, higher-order brain regions are involved to safely store robust memory contents.
To further understand the representations of visual working memory, I examined the formats of visual working memory and the imagery-versus-propositional debate in specific. Comparing across conditions, I found visual working memory contents consisted of analog constituents which are bound together. Single features like color and orientation are represented in a continuous fashion whereas the bindings between features are brokable to an extent like discrete propositions. This leads to a follow-up question: whether representations are created equal in visual working memory? It is known that items in the same feature domain are not represented equally in visual working memory, this dissertation looks at the binding components, are they created equal? Given the same experiment settings where the only difference is the spatial layouts of bindings between features, participants committed more swap errors when stimuli are vertically stacked than horizontally placed, suggesting a difference in binding strength in memory representations.
Lastly, this dissertation explored the relationship between information and the limited capacity of visual working memory representation, and the key process that mediates the relationship. Complexity limits the memory capacity, and this effect is established via the consolidation process
Electrochemical Engineering for Critical Elements Recovery and Utilization
No full textToday, non-renewable energy sources are still dominating the world's energy consumption. Carbon dioxide emitted from the combustion of fossil fuels has caused the greenhouse effect and raised serious concerns about the inevitable consequences to the atmosphere, ocean, and all living creatures. Transportation counts as one of the largest sectors of carbon emissions; therefore, finding an alternative solution to replace the current internal combustion engine has become imperative for a sustainable future. Electrochemical energy conversion devices such as Lithium-ion batteries and fuel cells are the most promising options. However, their massive application was hindered by the high cost and resource limitations of several critical elements, for example, lithium in LIB and platinum for PEMFC. This dissertation aims to investigate the electrochemical systems that potentially improve the recovery and utilization of these critical elements.
An electrochemical system employing a solid-state electrolyte membrane was investigated for continuous lithium extraction from brine and seawater. The system exhibited 95.7% total energy efficiency and nearly 100% selectivity to extract over 200 μg·cm-2h-1 lithium from artificial brines or seawater from the Inner Habor of Baltimore. The system also demonstrates good profitability; when operating at 0.25 mA·cm-2, the average price of produced LiOH is estimated to be $19.8/kg.
Additionally, two kinds of nanomaterials with carefully designed compositions, morphologies, and structures were developed for the fuel cell's cathode reaction, oxygen reduction reaction (ORR). Core-shell electrocatalysts with low platinum-group metal content and tunable surface strains were investigated; a platinum-based multi-principal element alloy (MPEA) electrocatalyst was also developed. Both catalysts exhibited significant enhancement of ORR activity compared to commercial Pt catalysts. The design and synthetic approach of these two kinds of nanostructures as electrocatalysts for ORR reveal their structure-property-performance relationships that can be used to guide the improvement and optimization of the activity and stability of electrocatalysts in the future
DEEP LEARNING-BASED METHODS FOR IMPROVING ACCELERATED MAGNETIC RESONANCE IMAGE RECONSTRUCTION
No full textAccelerating magnetic resonance imaging (MRI) reconstruction is a challenging ill-posed inverse problem. In this thesis, we work on topics related to MRI with vision-based intelligence. Specifically, our works focus on the topic of accelerated MRI reconstruction, which is faced with numerous obstacles such as imaging artifacts introduced by excessive under-sampling operation in k-space, the inherent data scarcity of medical images, etc. These challenges have significantly hindered the effectiveness and reliability of previous approaches. To this end, we propose a series of methods that utilize the expressive power of deep learning to address the challenges of accelerated MRI reconstruction. We first propose an MRI reconstruction method with state-of-the-art performance that leverages an overcomplete and an undercomplete recurrent neural network to focus more on low-level features without losing out on the global structures. To jointly exploit intrinsic multi-scale information at every architecture unit and the dependencies of the deep feature correlation through recurrent states, we introduce a recurrent Transformer model for MRI reconstruction which can iteratively reconstruct high-fidelity magnetic resonance images from highly under-sampled data. A reference-based MRI reconstruction pipeline is then proposed to facilitate joint feature learning across under-sampled and reference data, in which feature correspondences can be discovered by attention and accurate texture features can be leveraged. Then, we present several attempts to deal with the data scarcity issue in medical image analysis via federated learning and data synthesis. To enable multi-modal MR images synthesis, we propose a confidence-guided network that can simultaneously generate data from lesion contour information to five MR sequences, including T1-weighted, gadolinium-enhanced T1-weighted, T2-weighted, and fluid-attenuated inversion recovery, and the molecular amide proton transfer-weighted sequence via paired/unpaired data learning. To empower multi-institutional MRI reconstruction collaborations, a federated learning algorithm is proposed for MRI image reconstruction, where cross-site modeling for MR image reconstruction is introduced to overcome the data heterogeneity issue. Last but not least, an efficient reinforcement learning-based federated hyperparameter optimization framework is established, in which an online agent can dynamically adjust the hyperparameters of each client based on the current training progress within a single trial
Losing the War on Poverty: How the Underlying Philosophy of America’s Largest Anti-Poverty Programs Limits Upward Economic Mobility for People in Poverty
No full textAmerica's anti-poverty programs, notably those developed from Lyndon B. Johnson's Great Society initiative, have been built around the goal of eradicating poverty. America’s implementation of anti-poverty programs catalyzed the federal government to invest billions of dollars yearly toward addressing the variables contributing to poverty. These variables include the financial insecurities prevalent in various sectors of society, such as insurance and social security. Despite these investments, decades of data regarding the impact of anti-poverty programs and their effect on poverty have suggested a stagnated trend in the American poverty rate. Three main themes will be the subject of critical analysis. These themes are the philosophical basis of how anti-poverty programs were conceived, the historical impact of anti-poverty programs and their structural limits in alleviating poverty, and potential policies that can provide pathways for upward economic mobility for individuals in poverty. Thus, this paper will identify the thematic patterns of how Americans view poverty and how that affects the efficacy of anti-poverty programs. Conducting a critical analysis of the structural limitations of American anti-poverty policies and initiatives can be an opportunity to provide clarity for political leaders and the broader American public's capacity to understand how to address poverty
DEVELOPING AND APPLYING A KNOWLEDGE TRANSLATION FRAMEWORK TO EVALUATE REMOTE CAPACITY BUILDING WORKSHOPS IN NIGERIA AND INDIA THROUGH THE STRIPE INITIATIVE
No full textBackground
Workshops are a common Knowledge Translation (KT) tool in Public Health to build capacity in a relatively short period of time, especially for working professionals. This research aims to better understand the impact of remote methods on workshops and conduct an evaulation on impact of two remote workshops conducted as part of the STRIPE (Synthesis and Translation of Research and Innovations from Polio Eradication) initiative.
These papers will do the following. First conduct a literature review to outline the strengths, weaknesses opporuntity and threats associated with using remote workshops and identify the best practices to mitigate those weaknesses and threats. Second, develop a new conceptual framework leveraging KT, learning evaluation and implementation science theories to generate a consolidated framework to evaluate multi-site workshops. Third, implement the tools generated from that framework to evaluate changes in knowledge and self-efficacy from the two workshops conducted as part of the STRIPE initiative.
Methods
The first manuscript will be conducted using a PRISMA literature review methodology followed by content analysis to develop themes for the analysis. The second manuscript will follow Jabareen’s methodology for generating conceptual frameworks and the third manuscript will implement a traditional pre-post survey to collect information about the workshop and the participants to evaluate the impact and efficacy of the workshop. Statistical comparisons will be done via the McNemar test.
Results
The first manuscript outlines that remote workshops are feasible and may have more advantages compared to in-person but there are unique pitfalls to a remote model including ensuring technology access, usability, and engagement. The main best practice identified was taking the time to appropriately plan, adapt and implement a remote workshop. The conceptual framework developed for evaulation was a blending of 24 concepts, classified over 2 levels of context and 5 steps of knowledge translation from engagement to behavior change. The two STRIPE workshops were evaluated using this framework, demonstrated modest gains in knowledge and self-efficacy; however, identifying co-variates was difficult due to sample size and lack of qualitative. The use of the novel framework provided a unique lens in evaluating the STRIPE’s multi-site workshops showing that adaptions and different implementation styles had an impact on the evaluation outcomes.
Conclusions
Overall, this body of research provides a practical guide for educators when planning remote workshops, a set of tools to evaluate those workshops and an example of how those workshops could be evaluated. Future research is required to validate the conceptual framework
ZIC3 IS AN ESSENTIAL REGULATOR OF CONE PHOTORECEPTOR DEVELOPMENT
Get PDF13-line ground squirrel(13-LGS) is one of the rare diurnal rodents with cone-dominant retinas. A comprehensive large-scale single-cell comparative genomics study previously conducted in our lab revealed significant differences in cone development patterns between the 13-LGS and the rod-dominant mouse, characterized by an extended period of cone generation into the postnatal period in 13-LGS. A list of candidate genes was selected based on their differential expression patterns between 13-LGS and mice, among which Zic3 was our top candidate for further investigation. While Zic3 expression is strictly restricted to early-stage retinal progenitors (RPCs) in mice, it is also robustly expressed in late-stage RPCs and cone cells in 13-LGS, indicating a potential role for Zic3 in promoting cone photoreceptor specification and differentiation. To investigate this potential role of Zic3 in regulating cone photoreceptor development, Zic3 conditional knockout and overexpression models were generated, then analyzed with immunostaining and single-cell RNA sequencing. Selective disruption of Zic3 expression during early retinal development resulted in a reduction of cone cell density, while in vivo overexpression of Zic3 in late-stage RPCs that do not normally generate cones induced photoreceptor to translocate towards the apical retina, mirroring the normal location of cone photoreceptor nuclei. Co-electroporation of Zic3 and Pou2f1, which also promotes cone photoreceptor specification and shows expanded expression in developing 13-LGS retina, in ex vivo retinal explants resulted in a synergistic increase in generation of early-born retinal cell types, including cone photoreceptors, and suppression of rod-specific genes. Ex vivo overexpression of the transcription factor Onecut1, which also shows expanded expression in late-stage RPCs in 13-LGS, also strongly inhibited expression of rod-specific genes such as Nr2e3. These findings validated the role of transcription factor Zic3 in promoting cone specification during retinal development and potentially provided a new insight for the realization of directed induction of cone cell differentiation in stem cell therapy
PASS SWORD Test - Host Only
No full textTHis configuration has the endpoint for SWORD v2 configured without specifying a port numbe
Liberatory Fiction: Alternate Future Making of Black Women from Enslavement to #SayHerName
No full textLiberatory Fiction: Alternate Future Making of Black Women from Enslavement to #SayHerName interrogates the effectiveness of Black speculative fiction, and more specifically the visionary fiction genre, a term coined by Walidah Imarisha and adrienne maree brown in 2015, in aiding Black social justice movements in the United States. Visionary fiction, which is more accurately referred to as liberatory fiction in this dissertation, pushes the genre of Black speculation and Afrofuturism further to create space for the imagination to envision alternate futures, and sometimes pasts, that rewrite history to aid in the process of liberation for Black lives. The intended outcome of visionary fiction texts is the liberation of their subjects and, in some cases, their readers. The liberation of subjects comes in the form of attaining collective or personal freedoms. In more canonical literary genres such as the slave narrative, and traditional speculative and science fiction, Black women characters are treated as commodities and sites of violence, but visionary fiction, I argue, counters these representations. Building upon theories by Hortense Spillers, Saidiya Hartman, and W.E.B. Du Bois, Liberatory Fiction: Alternate Future Making of Black Women from Enslavement to #SayHerName, presents a case for the value of the genre for Black women. With a combination of both canonical African American literature, such as slave narratives by Harriet Jacobs and Frederick Douglass, and historical fiction of Toni Morrison, and speculative fiction by authors W.E.B. Du Bois, Octavia E. Butler, and N.K. Jemisin, this dissertation argues that these narratives, graphic novels, murals, and television, amplify both the spectacle of trauma and offer possibilities of liberation, presenting spectators with real-world scenarios that expose the ails of the United States and reflect the rallying cry of the Black Lives Matter Global Network