Essays in monetary economics

2024This dissertation consists of three chapters on macroeconomics and monetary economics. In the first chapter, I provide an equilibrium model of the pass-through of direct central bank lending to banks (CBL) into loans and quantitatively analyze the most significant such policy, the ECB’s Targeted Long Term Refinancing Operations (TLTRO). The banking sector features bank market power in deposits and lending, and banks borrow funds from the central bank and choose to adjust deposits, liquid asset holdings, and loans. I embed this into a New Keynesian model in which aggregate loan demand and deposit supply are endogenous. I calibrate the model to match the cross-sectional empirical literature on TLTRO, allowing me to translate these micro estimates into an aggregate impact of CBL. I find a 32% pass-through of CBL into bank lending; correspondingly, an increase in central bank lending of 10% of outstanding loans provides stimulus equivalent to a 54 basis point cut to the policy rate. The model also implies that CBL will be more effective when banks hold few liquid assets and lending markets are more competitive.In the second chapter, I study how conventional and unconventional monetary policies differentially affect lending by banks in the United States. Using bank-level data and high-frequency instruments for standard monetary shocks and quantitative easing, I find that the two policies predominantly affect different types of banks as measured by their balance sheets. Interest rate shocks have a stronger impact on loans for banks that are illiquid, bigger, less capitalized, and less reliant on deposit funding. The opposite is true for quantitative easing shocks, where loans decline more in banks that are liquid, smaller, more capitalized, and more reliant on deposit funding. The amount of heterogeneity is large, with the more affected banks having a two to three times larger response of lending after three years. The last chapter studies the fact that low-skilled workers tend to display both more cyclical employment and more cyclical earnings compared to high-skilled workers. I develop a model with wage stickiness, differential labor market frictions, and two sectors employing separately high and low-skilled workers. Firms face two cost components when they adjust employment: the wage paid to new employees and hiring costs. Although wages are more flexible in the low-skill sector, the hiring cost is more volatile in the high-skill sector. The implication is that total costs are more volatile for high-skilled workers, thus leading to a lower cyclicality in their employment while also preserving a lower cyclicality in their wages. The result is driven by different matching function elasticities (or equivalently bargaining powers) and Frisch elasticities for high and low-skilled workers

Examining whether prior knowledge of cervical cancer can lead to positive attitudes and behaviors towards cancer prevention

2024PURPOSE: Cervical cancer poses a significant global health challenge, ranking as the fourth most common cancer among women worldwide, according to the World Health Organization. The aim of this study is to examine the impact of prior knowledge of cervical cancer on attitudes and behaviors toward cancer prevention. SUBJECT AND METHODS: We conducted a cross-sectional study of 100 participants who completed surveys assessing their knowledge of Human papillomavirus (HPV), cervical cancer causes, risk reduction strategies, vaccines, screening methods, and perceived cancer risk and vaccination behaviors. The population for this study comprised parents whose children were enrolled in the clinical trial titled "An Exploratory Open-Label Clinical Trial Evaluating the Immunogenicity and Safety of the 9vHPV 2-Dose Vaccine Regimen in Children Aged 4–8 Years” at Boston Medical Center. RESULTS: The average age of the participants was 35.65 years (SD = 8.58, n = 98). Regarding gender distribution, 14.58% identified as male, 84.38% as female, and 1.04% as non-binary (n = 96). The ethnic composition of the sample was diverse, with 57.14% identifying as African American, 15.31% as Hispanic, 2.04% as Asian, 5.10% as White, and 14.29% as Other (n = 98). 2.04% reporting no education, 1.02% primary education, 41.84% middle school education, 12.24% high school education, 41.84% obtaining a GED, and 1.02% having some college education (n = 98). The results revealed several statistically significant associations. Prior knowledge of the cause of cervical cancer was significantly associated with the perceived importance of cancer prevention (χ2 = 15.2538, p = 0.0184). Similarly, knowledge of cervical cancer risk reduction was significantly associated with the perceived importance of cancer prevention (χ2 = 23.2341, p = 0.0007). Knowledge of the cervical cancer vaccine was also significantly associated with the perceived importance of cancer prevention (χ2 = 12.5993, p = 0.0499). Additionally, knowledge of Pap smears was significantly associated with the perceived importance of cancer prevention (χ2 = 15.3223, p = 0.0041). The study found a significant association between knowledge of HPV cervical cancer risk and HPV vaccine reception (Fisher's Exact Test, p < 0.0001), as well as between knowledge of HPV-related genital warts and HPV vaccine reception (Fisher's Exact Test, p = 0.0407). Furthermore, knowledge of HPV causing cervical cancer was significantly associated with perceived cancer risk (Fisher's Exact Test, p = 0.0319). CONCLUSION: Enhancing tailored knowledge about HPV and cervical cancer is pivotal in increasing HPV vaccination rates and reducing the burden of cervical cancer. This study underscores the critical role of targeted education in shaping perceptions and behaviors related to cervical cancer prevention among susceptible communities. Future interventions should address knowledge gaps and improve vaccine acceptance through multifaceted approaches.

The effect of statin treatment on developmental angiogenesis in zebrafish

2024Atherosclerosis is the leading cause of cardiovascular disease globally and is characterized by the accumulation of low density lipoprotein cholesterol (LDL-C) in the sub-endothelial space of arteries. Statins have proven effective at lowering LDL-C and protecting against atherogenic risk. However, the effect of statin on early vascular development, including intussusceptive and sprouting angiogenesis, proves inconclusive suggesting both pro- and anti-angiogenic effects. In this study, we treated wild type (wt) and low-density lipoprotein receptor (ldlr) knockout (Tg:flk:GFP) zebrafish with atorvastatin and simvastatin at 1-day post fertilization (1dpf) and 24 hours later at 2-days post-fertilization (2dpf) we quantified survival (%), intracranial hemorrhage (ICH) (%), and developmental angiogenesis in the dorsal aorta (DA), caudal venous plexus (CVP) and intersegmental vessels (ISV). Our findings demonstrate ldlr mutant zebrafish treated with lethal doses of 50 nM atorvastatin and 100 nM simvastatin demonstrated a significant reduction in intersegmental vessels compared to wt. Furthermore, ldlr mutant zebrafish had significantly greater number of intussusceptive pillars in both untreated and sublethal statin treatment (10 nM atorvastatin and 1 nM simvastatin) compared to wt zebrafish. Additionally, there was a dose-dependent effect on survival and ICH for both atorvastatin and simvastatin treated wt and ldlr mutant genotypes. Moreover, ldlr homozygous mutants treated with atorvastatin but not with simvastatin demonstrated a protective effect on statin-induced lethality compared to wt zebrafish. Despite the enhanced survival of ldlr mutant zebrafish with doses of statin lethal in wild-type fish, our findings suggest an exaggerated anti-angiogenic effect for both sprouting angiogenesis and intussusceptive angiogenesis in ldlr knockout. The results presented in this work sets the foundation for mechanistic studies and further exploration of distinguishing pro-angiogenic and anti-angiogenic effects, such as looking at endothelial cell turnover and cytoskeletal structure in the characterized vascular phenotypes presented in this study

Dynamic nonparametric learning for nonstationary time series data

2024This dissertation focuses on analyzing nonstationary time series data that presents significant challenges to traditional statistical methods due to the changing aspects of the underlying data-generating mechanism, like the mean, variance, and others over time. To address this issue, we propose innovative nonparametric methods, including a stratified penalization method for time-varying regressions, multi-output time-varying regressions, time-varying second-order moment and correlation function estimation, specifically designed for data with evolving dynamics. We provide the theoretical properties of the proposed nonparametric methods and the computing algorithms for obtaining the nonparametric estimations. We also present numerical results and Monte Carlo simulations to examine the finite sample performance. Furthermore, we considered the application of our methods from various fields, such as finance and environmental science, that involved dynamic time series analysis

Journal of African Christian Biography: v. 8, no. 4: Separate cover file (PDF), print-ready

The full issue of Journal of African Christian Biography: v. 8, no. 4 is available at: https://hdl.handle.net/2144/4696

Fabrication and excitation transfer investigation of chalcopyrite nanocrystals-gold nanoparticle hybrid structures

2025Hybrid structures composed of chalcopyrite nanocrystals embedded into the lipid coating of noble metal nanoparticles show significant potential for advancing applications in plasmon-enhanced photocatalysis, electrocatalysis, and solar cell technologies. While previous works have studied chalcopyrite’s quasistatic resonance in the visible region with silver nanoparticles, gold-based hybrid structures remain underexplored. This work optimized the fabrication of gold-based hybrid structures and investigated the excitation transfer between the two components via single-particle spectroscopy and simulations. The energetic mismatch with the gold plasmon (~550 nm) overlapping with the low-energy tail of the chalcopyrite’s quasistatic resonance (460–510 nm) seems to make gold nanoparticles less suited to engineer excitation transfer than silver nanoparticles, whose plasmon (~450 nm) shows better overlap with the chalcopyrite quasistatic resonance. These findings decisively enhance our understanding of the energetic interactions between plasmonic metal and “semiconductor” nanostructures that sustain collective quasistatic resonances in bi-resonant hybrid structures

Journal of African Christian Biography: v. 5, no. 4: Separate cover file (PDF), print-ready

The full issue of Journal of African Christian Biography: v. 5, no. 4 is available at: https://hdl.handle.net/2144/4158

Journal of African Christian Biography: v. 1, no. 6: Separate cover file (8.5 x 11 format), print-ready

The full issue of Journal of African Christian Biography: v. 1, no. 6 is available at: https://hdl.handle.net/2144/3566

Essays in real estate and urban economics

2025This dissertation consists of three chapters on real estate and urban economics. They examine how market forces and government policies affect distributional outcomes in the residential real estate market. The first chapter examines the shift in new construction toward larger, more expensive homes. I study the causes of this pattern and evaluate the equilibrium impacts of proposed housing policies aimed at improving affordability at the lower end of the market. I develop an equilibrium model of segmented housing markets with two key features: (1) heterogeneous household preferences for housing quality by demographics, and (2) endogenous housing supply with heterogeneous development costs by housing quality. Using microdata on household housing choices and parcel-specific development costs for single-family homes in the Atlanta MSA, I find that the shift toward large home construction is partly driven by demand from high-income households, who are less price-sensitive and prefer larger homes, but zoning density restrictions play a more significant role in limiting the construction of smaller homes. Relaxing these restrictions could expand the supply of small homes and benefit low-income households, but such zoning reforms are often politically challenging. As an alternative, I evaluate the impact of recently proposed housing subsidies targeting first-time homebuyers and starter homes. The model predicts that subsidizing young, low-income households provides substantial targeted welfare gains to recipients but hurts others due to rising prices. By contrast, subsidies to small home construction increase the supply of small homes but crowd out the construction of larger homes, resulting in modest welfare gains without effectively targeting those most in need. The second chapter, co-authored with Leonel Diego Drukker, examines the financial disparities Black homeowners face during the home-selling process. Using repeat-sale transactions from 2003 to 2020, we document that Black homeowners earn, on average, 0.36% lower annualized unlevered returns than non-Black sellers for similar properties. These racial disparities in housing returns cannot be explained by seller characteristics, property renovations, the buyer's race, seller agent fixed effects, and appraisal measures. However, we find significant racial gaps in listing prices and time on market, which we attribute to intermediaries involved in housing transactions. Controlling for these factors reduces the racial gap in returns to effectively zero. Additionally, we find that when homes are sold to iBuyers, where human intermediary bias is removed, the racial gap in housing returns disappears. Our findings suggest that Black sellers experience higher search frictions, leading to worse selling outcomes. The third chapter focuses on the entry of large institutional investors into the single-family rental market. Since 2012, institutional buy-to-rent (B2R) investors have entered the single-family rental market, converting a substantial number of owner-occupied homes into rental properties. This study examines the impact of B2R investors on nearby property values, providing reduced-form evidence on the size and origin of spillover effects resulting from their presence. I find that an additional property by B2R investors within 150 meters increases housing price growth by 2-3%. The impact is more pronounced in neighborhoods with a higher share of Black residents and lower property values. The reduced supply of owner-occupied housing and improvements in local amenities are key factors driving the positive spillover effects on housing prices

Exercise and Alzheimer’s disease in individuals with Down syndrome

2024Individuals with Down syndrome (DS) face a heightened risk of developing Alzheimer's disease (AD) due to triplication of chromosome 21, which harbors the amyloid precursor protein (APP) gene. The resultant overexpression of APP leads to elevated amyloid plaque production, a hallmark of AD neuropathology. With increasing longevity, age-related dementia of the AD type is prevalent in people with DS. Given the need for targeted interventions, we explore exercise as a potential avenue to mitigate AD onset in this vulnerable population. While exercise is known to modulate AD pathways in the general population, its specific effects on individuals with DS remain understudied. We review three AD pathophysiological pathways—oxidative stress, mitochondrial dysfunction, and neuroinflammation—and highlight evidence demonstrating exercise's potential to modify these pathways. Clinical trials in the general population demonstrate exercise's efficacy in reducing neuroinflammation and oxidative stress, suggesting its promise as a non-pharmacological intervention for AD. Longitudinal exercise studies in DS are lacking, warranting further investigation into exercise-induced biomarkers and neuroprotective mechanisms. To advance this field, blood-based biomarker exploration and longitudinal studies are needed in further exercise trials in individuals with DS. This review serves to establish a framework to deepen the knowledge where comprehensive data exists, such as oxidative stress studies. The framework also extends to where there is a paucity of data, including mitochondrial dysfunction and neuroinflammation. Future research should focus on elucidating exercise-induced biomarkers, optimizing exercise prescriptions, and exploring novel pathways, ultimately paving the way for effective AD prevention and management strategies in this vulnerable population and beyond