4 resultados para Persistence of Profits

em Duke University


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This dissertation seeks to advance our understanding of the roles that institutions play in economic development. How do institutions evolve? What mechanisms are responsible for their persistence? What effects do they have on economic development?

I address these questions using historical and contemporary data from Eastern Europe and Russia. This area is relatively understudied by development economists. It also has a very interesting history. For one thing, for several centuries it was divided between different empires. For another, it experienced wars and socialism in the 20th century. I use some of these exogenous shocks as quasi-natural social experiments to study the institutional transformations and its effects on economic development both in the short and long run.

This first chapter explores whether economic, social, and political institutions vary in their resistance to policies designed to remove them. The empirical context for the analysis is Romania from 1690 to the 2000s. Romania represents an excellent laboratory for studying the persistence of different types of historical institutional legacies. In the 18th and 19th centuries, Romania was split between the Habsburg and Ottoman Empires, where political and economic institutions differed. The Habsburgs imposed less extractive institutions relative to the Ottomans: stronger rule of law, a more stable and predictable state, a more developed civil society, and less corruption. In the 20th century, the Romanian Communist regime tried deliberately to homogenize the country along all relevant dimensions. It was only partially successful. Using a regression discontinuity design, I document the persistence of economic outcomes, social capital, and political attitudes. First, I document remarkable convergence in urbanization, education, unemployment, and income between the two former empires. Second, regarding social capital, no significant differences in organizational membership, trust in bureaucracy, and corruption persist today. Finally, even though the Communists tried to change all political attitudes, significant discontinuities exist in current voting behavior at the former Habsburg-Ottoman border. Using data from the parliamentary elections of 1996-2008, I find that former Habsburg rule decreases by around 6 percentage points the vote share of the major post-Communist left party and increases by around 2 and 5 percentage points the vote shares of the main anti-Communist and liberal parties, respectively.

The second chapter investigates the effects of Stalin’s mass deportations on distrust in central authority. Four deported ethnic groups were not rehabilitated after Stalin’s death; they remained in permanent exile until the disintegration of the Soviet Union. This allows one to distinguish between the effects of the groups that returned to their homelands and those of the groups that were not allowed to return. Using regional data from the 1991 referendum on the future of the Soviet Union, I find that deportations have a negative interim effect on trust in central authority in both the regions of destination and those of origin. The effect is stronger for ethnic groups that remained in permanent exile in the destination regions. Using data from the Life in Transition Survey, the chapter also documents a long-term effect of deportations in the destination regions.

The third chapter studies the short-term effect of Russian colonization of Central Asia on economic development. I use data on the regions of origin of Russian settlers and push factors to construct an instrument for Russian migration to Central Asia. This instrument allows me to interpret the outcomes causally. The main finding is that the massive influx of Russians into the region during the 1897-1926 period had a significant positive effect on indigenous literacy. The effect is stronger for men and in rural areas. Evidently, interactions between natives and Russians through the paid labor market was an important mechanism of human capital transmission in the context of colonization.

The findings of these chapters provide additional evidence that history and institutions do matter for economic development. Moreover, the dissertation also illuminates the relative persistence of institutions. In particular, political and social capital legacies of institutions might outlast economic legacies. I find that most economic differences between the former empires in Romania have disappeared. By the same token, there are significant discontinuities in political outcomes. People in former Habsburg Romania provide greater support for liberalization, privatization, and market economy, whereas voters in Ottoman Romania vote more for redistribution and government control over the economy.

In the former Soviet Union, Stalin’s deportations during World War II have a long-term negative effect on social capital. Today’s residents of the destination regions of deportations show significantly lower levels of trust in central authority. This is despite the fact that the Communist regime tried to eliminate any source of opposition and used propaganda to homogenize people’s political and social attitudes towards the authorities. In Central Asia, the influx of Russian settlers had a positive short-term effect on human capital of indigenous population by the 1920s, which also might have persisted over time.

From a development perspective, these findings stress the importance of institutions for future paths of development. Even if past institutional differences are not apparent for a certain period of time, as was the case with the former Communist countries, they can polarize society later on, hampering economic development in the long run. Different institutions in the past, which do not exist anymore, can thus contribute to current political instability and animosity.

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Urinary tract infections (UTIs) are typically caused by bacteria that colonize different regions of the urinary tract, mainly the bladder and the kidney. Approximately 25% of women that suffer from UTIs experience a recurrent infection within 6 months of the initial bout, making UTIs a serious economic burden resulting in more than 10 million hospital visits and $3.5 billion in healthcare costs in the United States alone. Type-1 fimbriated Uropathogenic E. coli (UPEC) is the major causative agent of UTIs, accounting for almost 90 % of bacterial UTIs. The unique ability of UPEC to bind and invade the superficial bladder epithelium allows the bacteria to persist inside epithelial niches and survive antibiotic treatment. Persistent, intracellular UPEC are retained in the bladder epithelium for long periods, making them a source of recurrent UTIs. Hence, the ability of UPEC to persist in the bladder is a matter of major health and economic concern, making studies exploring the underlying mechanism of UPEC persistence highly relevant.

In my thesis, I will describe how intracellular Uropathogenic E.coli (UPEC) evade host defense mechanisms in the superficial bladder epithelium. I will also describe some of the unique traits of persistent UPEC and explore strategies to induce their clearance from the bladder. I have discovered that the UPEC virulence factor Alpha-hemolysin (HlyA) plays a key role in the survival and persistence of UPEC in the superficial bladder epithelium. In-vitro and in-vivo studies comparing intracellular survival of wild type (WT) and hemolysin deficient UPEC suggested that HlyA is vital for UPEC persistence in the superficial bladder epithelium. Further in-vitro studies revealed that hemolysin helped UPEC persist intracellularly by evading the bacterial expulsion actions of the bladder cells and remarkably, this virulence factor also helped bacteria avoid t degradation in lysosomes.

To elucidate the mechanistic basis for how hemolysin promotes UPEC persistence in the urothelium, we initially focused on how hemolysin facilitates the evasion of UPEC expulsion from bladder cells. We found that upon entry, UPEC were encased in “exocytic vesicles” but as a result of HlyA expression these bacteria escaped these vesicles and entered the cytosol. Consequently, these bacteria were able to avoid expulsion by the cellular export machinery.

Since bacteria found in the cytosol of host cells are typically recognized by the cellular autophagy pathway and transported to the lysosomes where they are degraded, we explored why this was not the case here. We observed that although cytosolic HlyA expressing UPEC were recognized and encased by the autophagy system and transported to lysosomes, the bacteria appeared to avoid degradation in these normally degradative compartments. A closer examination of the bacteria containing lysosomes revealed that they lacked V-ATPase. V-ATPase is a well-known proton pump essential for the acidification of mammalian intracellular degradative compartments, allowing for the proper functioning of degradative proteases. The absence of V-ATPase appeared to be due to hemolysin mediated alteration of the bladder cell F-actin network. From these studies, it is clear that UPEC hemolysin facilitates UPEC persistence in the superficial bladder epithelium by helping bacteria avoid expulsion by the exocytic machinery of the cell and at the same time enabling the bacteria avoid degradation when the bacteria are shuttled into the lysosomes.

Interestingly even though UPEC appear to avoid elimination from the bladder cell their ability to multiple in bladder cells seem limited.. Indeed, our in-vitro and in-vivo experiments reveal that UPEC survive in superficial bladder epithelium for extended periods of time without a significantly change in CFU numbers. Indeed, we observed these bacteria appeared quiescent in nature. This observation was supported by the observation that UPEC genetically unable to enter a quiescence phase exhibited limited ability to persist in bladder cells in vitro and in vivo, in the mouse bladder.

The studies elucidated in this thesis reveal how UPEC toxin, Alpha-hemolysin plays a significant role in promoting UPEC persistence via the modulation of the vesicular compartmentalization of UPEC at two different stages of the infection in the superficial bladder epithelium. These results highlight the importance of UPEC Alpha-hemolysin as an essential determinant of UPEC persistence in the urinary bladder.

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This dissertation is comprised of three essays in the economics of education. In the first essay, I examine how college students' major choice and major switching behavior responds to major-specific labor market shocks. The second essay explores the incidence and persistence of overeducation for workers in the United States. The final essay examines the role that students' cognitive and non-cognitive skills play in their transition from secondary to postsecondary education, and how the effect of these skills are moderated by race, gender, and socioeconomic status.

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Human activities represent a significant burden on the global water cycle, with large and increasing demands placed on limited water resources by manufacturing, energy production and domestic water use. In addition to changing the quantity of available water resources, human activities lead to changes in water quality by introducing a large and often poorly-characterized array of chemical pollutants, which may negatively impact biodiversity in aquatic ecosystems, leading to impairment of valuable ecosystem functions and services. Domestic and industrial wastewaters represent a significant source of pollution to the aquatic environment due to inadequate or incomplete removal of chemicals introduced into waters by human activities. Currently, incomplete chemical characterization of treated wastewaters limits comprehensive risk assessment of this ubiquitous impact to water. In particular, a significant fraction of the organic chemical composition of treated industrial and domestic wastewaters remains uncharacterized at the molecular level. Efforts aimed at reducing the impacts of water pollution on aquatic ecosystems critically require knowledge of the composition of wastewaters to develop interventions capable of protecting our precious natural water resources.

The goal of this dissertation was to develop a robust, extensible and high-throughput framework for the comprehensive characterization of organic micropollutants in wastewaters by high-resolution accurate-mass mass spectrometry. High-resolution mass spectrometry provides the most powerful analytical technique available for assessing the occurrence and fate of organic pollutants in the water cycle. However, significant limitations in data processing, analysis and interpretation have limited this technique in achieving comprehensive characterization of organic pollutants occurring in natural and built environments. My work aimed to address these challenges by development of automated workflows for the structural characterization of organic pollutants in wastewater and wastewater impacted environments by high-resolution mass spectrometry, and to apply these methods in combination with novel data handling routines to conduct detailed fate studies of wastewater-derived organic micropollutants in the aquatic environment.

In Chapter 2, chemoinformatic tools were implemented along with novel non-targeted mass spectrometric analytical methods to characterize, map, and explore an environmentally-relevant “chemical space” in municipal wastewater. This was accomplished by characterizing the molecular composition of known wastewater-derived organic pollutants and substances that are prioritized as potential wastewater contaminants, using these databases to evaluate the pollutant-likeness of structures postulated for unknown organic compounds that I detected in wastewater extracts using high-resolution mass spectrometry approaches. Results showed that application of multiple computational mass spectrometric tools to structural elucidation of unknown organic pollutants arising in wastewaters improved the efficiency and veracity of screening approaches based on high-resolution mass spectrometry. Furthermore, structural similarity searching was essential for prioritizing substances sharing structural features with known organic pollutants or industrial and consumer chemicals that could enter the environment through use or disposal.

I then applied this comprehensive methodological and computational non-targeted analysis workflow to micropollutant fate analysis in domestic wastewaters (Chapter 3), surface waters impacted by water reuse activities (Chapter 4) and effluents of wastewater treatment facilities receiving wastewater from oil and gas extraction activities (Chapter 5). In Chapter 3, I showed that application of chemometric tools aided in the prioritization of non-targeted compounds arising at various stages of conventional wastewater treatment by partitioning high dimensional data into rational chemical categories based on knowledge of organic chemical fate processes, resulting in the classification of organic micropollutants based on their occurrence and/or removal during treatment. Similarly, in Chapter 4, high-resolution sampling and broad-spectrum targeted and non-targeted chemical analysis were applied to assess the occurrence and fate of organic micropollutants in a water reuse application, wherein reclaimed wastewater was applied for irrigation of turf grass. Results showed that organic micropollutant composition of surface waters receiving runoff from wastewater irrigated areas appeared to be minimally impacted by wastewater-derived organic micropollutants. Finally, Chapter 5 presents results of the comprehensive organic chemical composition of oil and gas wastewaters treated for surface water discharge. Concurrent analysis of effluent samples by complementary, broad-spectrum analytical techniques, revealed that low-levels of hydrophobic organic contaminants, but elevated concentrations of polymeric surfactants, which may effect the fate and analysis of contaminants of concern in oil and gas wastewaters.

Taken together, my work represents significant progress in the characterization of polar organic chemical pollutants associated with wastewater-impacted environments by high-resolution mass spectrometry. Application of these comprehensive methods to examine micropollutant fate processes in wastewater treatment systems, water reuse environments, and water applications in oil/gas exploration yielded new insights into the factors that influence transport, transformation, and persistence of organic micropollutants in these systems across an unprecedented breadth of chemical space.