Using state charitable tax subsidy rates to proxy for tax incentives, I examine the effect of donors’ charitable tax incentives on the relation between donor contributions and nonprofit organizations’ (NPOs) program efficiency, following Weisbrod and Dominguez (1986) who model a negative relation between charitable tax incentives and NPO program efficiency. I focus my study on NPOs with large donors (i.e., donors that make a single contribution of $5,000 or more) because large donors are more likely to be the beneficiaries of these tax incentives given that the incentives lower their after-tax cost of giving. In addition, NPOs typically appoint large donors to the board, which places these donors in a position to influence NPO efficiency. I use Form 990 Schedule B data to identify NPOs that have one or more large donors, and I find that as state tax rates increase, an increase in donor contributions is associated with higher NPO program efficiency. The results suggest that contrary to the expectations of Weisbrod and Dominguez (1986), tax incentives do not have a negative effect on NPO program efficiency in NPOs with large donors. Rather, my results are consistent with large donors having higher efficiency expectations and being more likely to ensure that the NPO operates efficiently. Given that large donors on the NPO’s board can influence NPO program efficiency and based on the expected negative effect of taxes on the relation between donor contributions and NPO program efficiency predicted by Weisbrod and Dominguez (1986), I further examine whether the effect of donor tax incentives on the relation between donor contributions and NPO program efficiency in NPOs with large donors differ by board size, board independence, and state regulations. While the coefficients indicate that tax incentives have a more positive effect on the relation between donor contributions and NPO program efficiency for NPOs with large board sizes compared to NPOs with small board sizes, Wald statistics indicate that the results do not differ statistically between NPOs split by board sizes. However, the results examining the effect of board independence indicate that NPO program efficiency is higher in NPOs with independent boards compared to those with non-independent boards, suggesting that an independent board has a positive differential impact on how tax incentives affect the relation between donor contributions and NPO program efficiency. Conversely, the results indicate that there is no statistical difference in the effect of tax incentives on the relation between donor contributions and NPO program efficiency between samples split by state regulations. Taken together, the results suggest that while NPO board size and state governance do not impact how tax incentives affect the relation between donor contributions and NPO program efficiency, an independent board has a positive impact on how tax incentives affect the relation between donor contributions and NPO program efficiency. In additional tests, I use changes in state tax rates to examine the effect of tax incentives on the relation between donor contributions and NPO program efficiency. The results show that state tax rate changes (decreases and increases) do not affect the relation between donor contributions and NPO program efficiency. I also conduct tests using federal tax changes to proxy for tax incentives. I first exploit the exogenous shock from the 2017 Tax Cuts and Jobs Act (TCJA) to examine changes in program efficiency, and the results are statistically insignificant, indicating that the TCJA had no effect on the relation between donor contributions and NPO program efficiency. Thereafter, I use the percentage of itemizers in each state as a proxy for tax incentives, and the results also suggest that the percentage of itemizers does not affect the relation between donor contributions and NPO program efficiency.

Cardiac diseases such as myocardial infarction (MI) can lead to adverse remodeling and impaired contractility of the heart due to widespread cardiomyocyte death in the damaged area. Current therapies focus on improving heart contractility and minimizing fibrosis with modest cardiac regeneration, but MI patients can still progress to heart failure (HF). There is a dire need for clinical therapies that can replace the lost myocardium, specifically by the induction of new myocyte formation from pre-existing cardiomyocytes. Many studies have shown terminally differentiated myocytes can re-enter the cell cycle and divide through manipulations of the cardiomyocyte cell cycle, signaling pathways, endogenous genes, and environmental factors. However, these approaches result in minimal myocyte renewal or cardiomegaly due to hyperactivation of cardiomyocyte proliferation. Finding the optimal treatment that will replenish cardiomyocyte numbers without causing tumorigenesis is a major challenge in the field. Another controversy is the inability to clearly define cardiomyocyte division versus myocyte DNA synthesis due to limited methods. A recent study suggests that systemic hypoxemia in adult male mice can induce cardiac myocytes to proliferate. The goal of the present experiments was to confirm these results, provide new insights on the mechanisms that induce cardiomyocyte cell cycle re-entry, and to determine if hypoxemia also induces cardiomyocyte proliferation and division in female mice. EdU mini pumps were implanted in 3-month-old, male and female C57BL/6 mice. Mice were then placed in a hypoxia chamber and the oxygen was lowered by 1% every day for 14 days to reach 7% oxygen. The animals remained in 7% inspired oxygen for 2 weeks before terminal studies. Myocyte cell cycle re-entry and division was also studied with a mosaic analysis with double markers (MADM) mouse model. MADM mice were exposed to hypoxia at 7% Oxygen as described above. Hypoxia induced cardiac hypertrophy in both left ventricular (LV) and right ventricular (RV) myocytes, with LV myocytes lengthening and RV myocytes widening and lengthening. Hypoxia induced a small increase in cardiomyocytes undergoing DNA synthesis (EdU+) in male and female C57BL/6 mice. Hypoxia induced a significant increase in myocyte cell cycle re-entry in MADM mice, but few myocytes synthesized new DNA (EdU+) and completed cytokinesis. RNA-sequencing showed upregulation in mitotic cell cycle processes but a downregulation of promoter genes for G1 to S phase transition in hypoxic mice when compared to control mice. There was also proliferation of non-myocyte cells and mild cardiac remodeling in hypoxic mice that did not disrupt cardiac function. Male and female mice exhibited similar gene expression profiles following hypoxia. Thus, systemic hypoxia induces adult cardiac myocyte cell cycle re-entry, but very few adult myocytes progress through the cell cycle to synthesize new DNA and divide into two daughter cells.

Complexes containing a transition metal atom with a 3d^4 - 3d^7 electron configuration typically have two low-lying, high spin (HS) and low spin (LS) states. The adiabatic energy difference between these states, known as the spin-crossover energy, is small enough to pose a challenge even for electronic structure methods that are well known for their accuracy and reliability. In this work we analyze the quality of electronic structure approximations for spin-crossover energies of iron complexes with four different ligands by comparing energies from self-consistent and post-self-consistent calculations for methods based on the random phase approximation and the Fermi-L\"{o}wdin self-interaction correction. Considering that Hartree-Fock densities were found by Song et al. J. Chem. Theory Comput. 14,2304 (2018) to eliminate the density error to a large extent, and that the Hartree-Fock method and the Perdew-Zunger-type self-interaction correction share some physics, we compare the densities obtained with these methods to learn about their resemblance. We find that evaluating non-empirical exchange-correlation energy functionals on the corresponding self-interaction-corrected densities can mitigate the strong density errors and improves the accuracy of the adiabatic energy differences between HS and LS states.

The classical spherical and Euclidean geometries are easy to visualize and correspond to spaces with constant curvature 0 and +1 respectively. The geometry with constant curvature −1, hyperbolic geometry, is much more complex. A powerful theorem of Mostow and Prasad states that in all dimensions at least 3, the geometry of a finite-volume hyperbolic manifold (a space with local d-dimensional hyperbolic geometry) is determined by the manifold's fundamental group (a topological invariant of the manifold). A cusp is a part of a finite-volume hyperbolic manifold that is infinite but has finite volume (cf. the surface of revolution of a tractrix has finite area but is infinite). All non-compact hyperbolic manifolds have cusps, but only finitely many of them. In the fundamental group of such a manifold, each cusp corresponds to a cusp subgroup, and each cusp subgroup is associated to a point on the boundary of H^d, which can be identified with the (d − 1)-sphere. It is known that there are many one-cusped two- and three-dimensional hyperbolic manifolds. This thesis studies restrictions on the existence of 1-cusped hyperbolic d-dimensional manifolds for d ≥ 3. Congruence subgroups belong to a special class of hyperbolic manifolds called arithmetic manifolds. Much is known about arithmetic hyperbolic 3- manifolds, but less is known about arithmetic hyperbolic manifolds of higher dimensions. An important infinite class of arithmetic d-manifolds is obtained using SO(n, 1; Z), a subset of the integer matrices with determinant 1. This is known to produce 1-cusped examples for small d. Taking special congruence conditions modulo a fixed number, we obtain congruence subgroups of SO(n, 1; Z) which also have cusps but possibly more than one. We ask what congruence subgroups with one cusp exist in SO(n, 1; Z). We consider the prime congruence level case, then generalize to arbitrary levels. Covering space theory implies a relation between the number of cusps and the image of a cusp in the mod p reduced group SO(d+ 1, p), an analogue of the classical rotation Lie group. We use the sizes of maximal subgroups of groups SO(d + 1, p), and the maximal subgroups' geometric actions on finite vector spaces, to bound the number of cusps from below. Let Ω(d, 1; Z) be the index 2 subgroup in SO(d, 1; Z) that consists of all elements of SO(d, 1; Z) with spinor norm +1. We show that for d = 5 and d ≥ 7 and all q not a power of 2, there is no 1-cusped level-q congruence subgroup of Ω(d, 1; Z). For d = 4, 6 and all q not of the form 2^a3^b, there is no 1-cusped level-q congruence subgroup of Ω(d, 1; Z).

n-Cyanoindole (n=2-7) fluorescent probes were developed for studying the structure and dynamics of proteins. It has been observed that cyano substitution at the 4-position of the bicyclic ring of indole dramatically increases the relative fluorescence intensity, lifetime, and quantum yield, while functionalizing other positions quenches the fluorescence in aqueous solution. We studied the positional substituent effect on the absorption and fluorescence properties using high-level quantum mechanical methods. In addition, we modeled the important solvation effects found in the interaction between the parent probe, indole, and water solvents using explicit solvation models and molecular dynamics simulations. We have unraveled the important non-radiative decay pathways that govern the fluorescence quenching of the probes in aqueous solution using water cluster models. It was found that upon excited state relaxation, water solvent stabilizes the La(ππ∗) excited state below the Lb(ππ∗) state when substitution takes place on the 6 membered ring causing (4-7)-cyanoindole to fluoresce from the bright La state and 2- and 3-cyanoindole to fluoresce from the dim Lb state. 4-cyanoindole was found to exhibit optimal fluorescence properties because it absorbs to and emits from the S1 excited state and has a high energy barrier in the S1 state potential energy surface along the N-H bond stretch which minimizes access to all non-radiative decay pathways. We also found that explicitly modeling the mutual polarization effects is essential to reproducing the features of the absorption spectrum of indole and the state inversion during fluorescence in aqueous solution. Furthermore, we found that the formation of a cyclic excimer structure results in different photochemical reaction paths such as excited state hydrogen transfer, excited state proton transfer, and excited state proton-coupled electron transfer processes, which if accessed, have the potential to rapidly quench the fluorescence intensity. However, the presence of a high energy barrier traps the 2-, 6-, and 7-cyanoindole-(H2O)1−2 clusters at the S1 state minimum, and thus the fluorescence is quenched due to vibrational relaxation and internal conversion from the S2 state at absorption to the S1 equilibrium geometry at emission.

DRAM-based memory system suffers from increasing aggravating row buffer interference, which causes significant performance degradation and power consumption. With DRAM scaling, the overheads of row buffer interference become even worse due to higher row activation and precharge latency. Clusters have been a prevalent and successful computing framework for processing large amount of data due to their distributed and parallelized working paradigm. A task submitted to a cluster is typically divided into a number of subtasks which are designated to different work nodes running the same code but dealing with different equal portion of the dataset to be processed. Due to the existence of heterogeneity, it could easily result in stragglers unfairly slowing down the entire processing, because work nodes finish their subtasks at different rates. With the increasing problem complexity, more irregular applications are deployed on high-performance clusters due to the parallel working paradigm, and yield irregular memory access behaviors across nodes. However, the irregularity of memory access behaviors is not comprehensively studied, which results in low utilization of the integrated hybrid memory system compositing of stacked DRAM and off-chip DRAM. This dissertation lists our research results on the above three mentioned challenges in order to optimize the memory system for high efficiency in computing clusters. Details are as follows: To address low row buffer utilization caused by row buffer interference, we propose Row Buffer Cache (RBC) architecture to efficiently mitigate row buffer interference overheads. At the core of the RBC architecture, the DRAM pages with good locality are cached and escape from the row buffer interference.Such an RBC architecture significantly reduces the overheads caused by row activation and precharge, thus improves overall system performance and energy efficiency. We evaluate our RBC using SPEC CPU2006 on a DDR4 memory compared to the commodity baseline memory system along with the state-of-art methods, DICE and Bingo. Results show that RBC improves the memory performance by up to 2.24X (16.1% on average) and reduces the overall memory energy by up to 68.2% (23.6% on average) for single-core simulations. For multi-core simulations, RBC increases the performance by up to 1.55X (16.7% on average) and reduces the energy by up to 35.4% (21.3% on average). Comparing with the state-of-art methods, RBC outperforms DICE and Bingo by 8% and 5.1% on average for single-core scenario, and by 10.1% and 4.7% for multi-core scenario. To relax the straggling effect observed in clusters, we aim to speed up straggling work nodes to quicken the overall processing by leveraging exhibited performance variation, and propose StragglerHelper which conveys the memory access characteristics experienced by the forerunner to the stragglers such that stragglers can be sped up due to the accurately informed memory prefetching. A Progress Monitor is deployed to supervise the respective progresses of the work nodes and inform the memory access patterns of forerunner to straggling nodes. Our evaluation results with the SPEC MPI 2007 and BigDataBench on a cluster of 64 work nodes have shown that StragglerHelper is able to improve the execution time of stragglers by up to 99.5% with an average of 61.4%, contributing to an overall improvement of the entire cohort of the cluster by up to 46.7% with an average of 9.9% compared to the baseline cluster. To address the performance difference in the irregular application, we devise a novel method called Similarity-Managed Hybrid Memory System (SM-HMS) to improve the hybrid memory system performance by leveraging the memory access similarity among nodes in a cluster. Within SM-HMS, two techniques are proposed, Memory Access Similarity Measuring and Similarity-based Memory Access Behavior Sharing. To quantify the memory access similarity, memory access behaviors of each node are vectorized, and the distance between two vectors is used as the memory access similarity. The calculated memory access similarity is used to share memory access behaviors precisely across nodes. With the shared memory access behaviors, SM-HMS divides the stacked DRAM into two sections, the sliding window section and the outlier section. The shared memory access behaviors guide the replacement of the sliding window section while the outlier section is managed in the LRU manner. Our evaluation results with a set of irregular applications on various clusters consisting of up to 256 nodes have shown that SM-HMS outperforms the state-of-the-art approaches, Cameo, Chameleon, and Hyrbid2, on job finish time reduction by up to 58.6%, 56.7%, and 31.3%, with 46.1%, 41.6%, and 19.3% on average, respectively. SM-HMS can also achieve up to 98.6% (91.9% on average) of the ideal hybrid memory system performance.

This dissertation examines how relatives of gun-violence victims, specifically Black women, move about their environments in the aftermath of sudden and tragic loss. I explore the following research questions: 1) How do Black women, who are co-victims of gun homicide, navigate spaces of trauma? 2) How does the experience of trauma extend into other spaces and spatialities of their lives? 3) What are the social, political, and health implications for Black women with limited mobility who are co-victims of gun homicide? This study draws on a literature synthesis on health geographies, geotrauma, and Black Feminist Geographies, as well as auto-methods, specifically a Black Feminist auto-ethnography (BFA). BFA involves analyzing your own experiences in relation to others in their family and community. My autoethnography of my lived experiences in the neighborhood I grew up in started with the observation of my mother in the aftermath of losing my brother to gun violence in 2012. My dissertation develops a research agenda to theorize how racism, poverty, and trauma compound and how Black women craft survival strategies as they navigate landscapes of trauma. I describe the ways that conventional approaches to understanding gun violence can overlook the layers of trauma and fail to capture the nuances or lived experience of being a co-victim of gun violence. I propose BFA to center and understand the lived experience of co-victims of gun violence and to bear witness to the ways we engage with the world around us while processing the trauma that is carried with us. My autoethnography uncovers key strategies my mother and I used to cope with our loss, especially in the face of institutional failures from the policy. This research points towards a need for better mental health resources for co-victims of gun violence as they process their grief.

This dissertation focusses on the discussion of how empirical ligand design works on the development of chiral pincer ligands in the field of asymmetric hydrogenation. Although the design art of bisphosphine ligands was well-established, this empirical guide for pincer ligand design is still ambiguous. Developing a ligand design guide based on the nature of metals enables synthetic chemists to improve the catalytic performance without investing large numbers of time, develop highly efficient catalysts for industrial uses, or explore new areas and mechanistic insights. Learning from the history of chiral pincer ligand development, over 14 categories of pincer ligands were reported according to the coordinating atoms by the time that this dissertation was prepared. Firstly, the ligand design and relevant catalytic performance of different ligand categories were summarized and discussed in prevalent noble metal catalysis such as Ru(II), Ir(III). Based on the nature of Fe(II) with respect to noble metals, a novel PNP-type ligand HengPNP (L) was designed and successfully synthesized. Empirical design perspectives were discussed, and the ligand was characterized by NMR, HRMS. Its corresponding Fe(II) complex was studied by X-ray crystallographic technique. However, the Fe(II) carbonyl complex was thermodynamically unstable under decent pressure. To better understand the catalytic performance and enantioselectivity of HengPNP(L), its corresponding Ir(III) complex was employed in the asymmetric hydrogenation of various ketone substrates. A C-H bond activation Ir(III) compound was successfully isolated. The Ir(III)/HengPNP was efficient on the asymmetric hydrogenation of orthosubstituted benzophenones with excellent ee and up to 500 TON. The catalyst was superior on the hydrogenation of bis-ortho-substituted benzophenones, excellent ee was achieved over the state-of-the-art Ir/f-amphox. DFT studies was conducted to shed light on the enantio-induction model of Ir/HengPNP. A novel enantio-induction mechanism was established-the change of rotation energy of ketone substrate under the steric pressure from rigid Ir/HengPNP, was responsible for the enantioselectivity. IrH/NH bifunctional mechanism was proposed for this protocol.

Adolescence is a unique developmental period where substantial brain development and social independence can result in higher risk-taking behavior. Researchers have spent the last several decades trying to understand at a neurological level why adolescents are more likely to take risks that often have extreme consequences (e.g., car accidents, drug use, etc.). The resulting research has found mixed and often inconsistent findings and scientists have posited that this could be due to differences in experimental tasks; where some are more description-based (e.g., Wheel of Fortune tasks) and others are more experience-based (e.g., Stop Signal tasks). Research examining the way adults learn about risk reveals that individuals make different decisions when information is learned via description or experience – a phenomenon known as the Description-Experience Gap. The present work aims to bridge research in adolescent development and judgement and decision-making to identify the neural processes associated with the Description-Experience gap in adolescents and adults. Across two studies, I examined the neural mechanisms associated with learning via description and experience in adolescents and adults and their subsequent impact on risky choice to find that adolescents and adults utilize information from description and experience differently. In adults, similar neural mechanisms involved with memory and deliberation are implicated at different points of the decision process. Adolescents displayed distinct neural activation associated with risk-taking and reward sensitivity when learning via experience. Both studies demonstrate the significance of memory and learning-relevant processes in risk-taking across development.

Three waves of tort reform occurred during mid-1970s, mid-1980s and early 2000s to deal with the liability “crises”. The inflationary pressures drove up the medical costs and social inflation pushed up the damage awards size, which led to the tort reform waves. We could see a potential today when the inflation continues to increase. Tort reforms have been widely studied for its impact on the litigation costs and benefits, through which physicians and insurers’ liability burden can be affected. While the liability markets have been relatively calm recently, legislative and academic debates over the efficacy of tort reforms and how they influence litigation behavior is not yet resolved. Whether tort reforms work to reduce the medical expenses and exert spillover effect on other insurance line market needs to be tested. A thorough analysis of tort reforms effect will benefit policymakers, regulators, insurers, and physicians and patients. This dissertation consists of three chapters to study how tort reforms affect the insurance markets, with a focus on health insurance markets. Chapter 1 assesses whether the effect of tort reform on the healthcare expenditures depends on the contract conditions under which physicians are paid for their professional services. Chapter 2 explores the potential for tort reforms to improve health insurers’ performance by boosting their efficiency. Chapter 3 looks at other types of state reforms and policies influencing liability costs to assess the effect on both medical liability and health insurance markets.