Essays on durable goods consumption and firm innovation

This dissertation comprises three individual chapters. Chapter Two examines how free riding across neighbors influenced the diffusion of color television sets in rural China. Chapter Three tests for asymmetric information between a firm’s management and other investors concerning its patent output. Chapter Four discusses how knowledge stocks influence a patenting firm’s later diversification. Chapter Two documents the existence of a type of network effects—free riding across neighbors—in the consumption of color television sets in rural China, which reduces the propensity of non-owners to purchase. I construct a model of the timing of the purchase of a durable good in the presence of free riding, and test its key implications using household survey data in rural China. Chapter Three tests for asymmetric information between a firm’s management and other investors about its patent output by examining insider trading patterns and stock price changes in R&D intensive firms. It demonstrates that management has considerable information about its patent output beyond what is known to investors. It also shows that the predictive power of insider trading patterns on patent output comes from purchases rather than sales. Chapter Four discusses two sequential channels through which knowledge stocks may influence a firm’s later diversification. One is that firms with more knowledge are more likely to enter a new industry. The other is that firms’ businesses have a better chance of surviving, conditional on being formed. By examining U.S. public patenting firms in manufacturing sectors for 1984-1996, I find that knowledge stocks predict the likelihood of new industry entry when controlling for firm size. However, this predictive power is weakened when diversification effects are included. On the other hand, a survival study of newly established segments shows that initial knowledge stocks have significant positive effects on segment survival, whereas diversification effects are insignificant.

Negotiating identities, striving for state recognition: Blacks in Córdoba, Argentina 1776–1853

Race in Argentina played a significant role as a highly durable construct by identifying and advancing subjects (1776–1810) and citizens (1811–1853). My dissertation explores the intricacies of power relations by focusing on the ways in which race informed the legal process during the transition from a colonial to national State. It argues that the State’s development in both the colonial and national periods depended upon defining and classifying African descendants. In response, people of African descendent used the State’s assigned definitions and classifications to advance their legal identities. It employs race and culture as operative concepts, and law as a representation of the sometimes, tense relationship between social practices and the State’s concern for social peace. This dissertation examines the dynamic nature of the court. It utilizes the theoretical concepts multicentric legal orders that are analyzed through weak and strong legal pluralisms, and jurisdictional politics, from the late eighteenth to early nineteenth centuries. This dissertation juxtaposes various levels of jurisdiction (canon/state law and colonial/national law) to illuminate how people of color used the legal system to ameliorate their social condition. In each chapter the primary source materials are state generated documents which include criminal, ecclesiastical, civil, and marriage dissent court cases along with notarial and census records. Though it would appear that these documents would provide a superficial understanding of people of color, my analysis provides both a top-down and bottom-up approach that reflects a continuous negotiation for African descendants’ goal for State recognition. These approaches allow for implicit or explicit negotiation of a legal identity that transformed slaves and free African descendants into active agents of their own destinies.

Enhanced anchorage of tissue-engineered cartilage using an osteoinductive approach

Articular cartilage injuries occur frequently in the knee joint. Several methods have been implemented clinically, to treat osteochondral defects but none have been able to produce a long term, durable solution. Photopolymerizable cartilage tissue engineering approaches appear promising; however, fundamentally, forming a stable interface between the tissue engineered cartilage and native tissue, mainly subchondral bone and native cartilage, remains a major challenge. The overall objective of this research is to find a solution for the current problem of dislodgment of tissue engineered cartilage at the defect site for the treatment of degraded cartilage that has been caused due to knee injuries or because of mild to moderate level of osteoarthritis. For this, an in-vitro model was created to analyze the integration of tissue engineered cartilage with the bone, healthy and diseased cartilage over time. We investigated the utility of hydroxyapatite (HA) nanoparticles to promote controlled bone-growth across the bone-cartilage interface in an in vitro engineered tissue model system using bone marrow derived stem cells. We also investigated the application of HA nanoparticles to promote enhance integration between tissue engineered cartilage and native cartilage both in healthy and diseased states. Samples incorporated with HA demonstrated significantly higher interfacial shear strength (at the junction between engineered cartilage and engineered bone and also with diseased cartilage) compared to the constructs without HA (p < 0.05), after 28 days of culture. These findings indicate that the incorporation of HA nanoparticles permits more stable anchorage of the injectable hydrogel-based engineered cartilage construct via augmented integration between bone and cartilage.^

Biocompatibility assessment of biosorbable polymer coated nitinol alloys

Owing to an increased risk of aging population and a higher incidence of coronary artery disease (CAD), there is a need for more reliable and safer treatments. Numerous varieties of durable polymer-coated drug eluting stents (DES) are available in the market in order to mitigate in-stent restenosis. However, there are certain issues regarding their usage such as delayed arterial healing, thrombosis, inflammation, toxic corrosion by-products, mechanical stability and degradation. As a result, significant amount of research has to be devoted to the improvement of biodegradable polymer-coated implant materials in an effort to enhance their bioactive response. ^ In this investigation, magneto-electropolished (MEP) and a novel biodegradable polymer coated ternary Nitinol alloys, NiTiTa and NiTiCr were prepared to study their bio and hemocompatibility properties. The initial interaction of a biomaterial with its surroundings is dependent on its surface characteristics such as, composition, corrosion resistance, work of adhesion and morphology. In-vitro corrosion tests such as potentiodynamic polarization and electrochemical impedance spectroscopic (EIS) studies were conducted to determine the coating stability and longevity. In-vitro hemocompatibility studies and HUVEC cell growth was performed to determine their thrombogenic and biocompatibility properties. Critical delamination load of the polymer coated Nitinol alloys was determined using Nano-scratch analysis. Sulforhodamine B (SRB) assays were performed to elucidate the effect of metal ions leached from Nitinol alloys on the viability of HUVEC cells. Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS), contact angle meter and X-ray diffraction (XRD) were used to characterize the surface of the alloys. ^ MEP treated and polymer coated (PC) Nitinol alloys displayed a corrosion resistant polymer coating as compared to uncoated alloys. MEP and PC has resulted in reduced Ni and Cr ion leaching from NiTi5Cr and subsequently low cytotoxicity. Thrombogenicity tests revealed significantly less platelet adhesion and confluent endothelial cell growth on polymer coated and uncoated ternary MEP Nitinol alloys. Finally, this research addresses the bio and hemocompatibility of MEP + PC ternary Nitinol alloys that could be used to manufacture blood contacting devices such as stents and vascular implants which can lead to lower U.S. healthcare spending.^

A Cross-Generational Analysis of Spanish-to-English Lexico-Semantic Phenomena in Emerging Miami English

Sociolinguists have documented the substrate influence of various languages on the formation of dialects in numerous ethnic-regional setting throughout the United States. This literature shows that while phonological and grammatical influences from other languages may be instantiated as durable dialect features, lexical phenomena often fade over time as ethnolinguistic communities assimilate with contiguous dialect groups. In preliminary investigations of emerging Miami Latino English, we have observed that lexical forms based on Spanish lexical forms are not only ubiquitous among the speech of the first generation Cuban Americans but also of the second. Examples, observed in field work, casual observation, and studied formally in an experimental context include the following: “get down from the car,” which derives from the Spanish equivalent, bajar del carro instead of “get out of the car”. The translation task administered to thirty-one participants showed a variety lexical phenomena are still maintained at equal or higher frequencies.

Race Relations & Politics in Venezuela during Punto Fijo (1958 – 1998)

In 1998, Hugo Chávez Frías’ presidential candidacy brought race to national discussion in Venezuela for first time since 1945. For long, the country’s politics had abided by the myth of racial harmony and racial democracy. This approach pointed to institutional separation in the United States and Africa as examples of true racism. Latin America was largely void of such atrocities. Nonetheless, Chávez claimed the present political parties (Acción Democrática, Copei and Unión Republicana Democrática) disenfranchised the common, colored Venezuelan. He continued to assert the opposition’s racism during his presidency. And his political fanbase agrees. A variety of scholars have studied the break from Punto Fijo politics to the Bolivarian Revolution. Yet, few have linked the obvious class struggle to race. Here, I seek to explain how racial identity has shaped class identity in Venezuela by closely examining the Punto Fijo era (1958-1998). The essay begins with an overview of historical race relations, moving to the period in focus. Then, I examine systematic and institutional exclusion under Punto Fijo politics. The object is to understand the merit of Chávez’s racial claims since 1998. Hence, the study also sees democracy in action and the consequences of racial exclusion. The study will be accomplished through secondary research, considering the limitations brought by working abroad. In the end, this study serves as first step in analyzing the fall of what was once considered Latin America’s most durable democracy.

Race Relations & Politics in Venezuela during Punto Fijo (1958 – 1998)

In 1998, Hugo Chávez Frías’ presidential candidacy brought race to national discussion in Venezuela for first time since 1945. For long, the country’s politics had abided by the myth of racial harmony and racial democracy. This approach pointed to institutional separation in the United States and Africa as examples of true racism. Latin America was largely void of such atrocities. Nonetheless, Chávez claimed the present political parties (Acción Democrática, Copei and Unión Republicana Democrática) disenfranchised the common, colored Venezuelan. He continued to assert the opposition’s racism during his presidency. And his political fanbase agrees. A variety of scholars have studied the break from Punto Fijo politics to the Bolivarian Revolution. Yet, few have linked the obvious class struggle to race. Here, I seek to explain how racial identity has shaped class identity in Venezuela by closely examining the Punto Fijo era (1958-1998). The essay begins with an overview of historical race relations, moving to the period in focus. Then, I examine systematic and institutional exclusion under Punto Fijo politics. The object is to understand the merit of Chávez’s racial claims since 1998. Hence, the study also sees democracy in action and the consequences of racial exclusion. The study will be accomplished through secondary research, considering the limitations brought by working abroad. In the end, this study serves as first step in analyzing the fall of what was once considered Latin America’s most durable democracy.

Biocompatibility Assessment of Biosorbable Polymer Coated Nitinol Alloys

Owing to an increased risk of aging population and a higher incidence of coronary artery disease (CAD), there is a need for more reliable and safer treatments. Numerous varieties of durable polymer-coated drug eluting stents (DES) are available in the market in order to mitigate in-stent restenosis. However, there are certain issues regarding their usage such as delayed arterial healing, thrombosis, inflammation, toxic corrosion by-products, mechanical stability and degradation. As a result, significant amount of research has to be devoted to the improvement of biodegradable polymer-coated implant materials in an effort to enhance their bioactive response. In this investigation, magneto-electropolished (MEP) and a novel biodegradable polymer coated ternary Nitinol alloys, NiTiTa and NiTiCr were prepared to study their bio and hemocompatibility properties. The initial interaction of a biomaterial with its surroundings is dependent on its surface characteristics such as, composition, corrosion resistance, work of adhesion and morphology. In-vitro corrosion tests such as potentiodynamic polarization and electrochemical impedance spectroscopic (EIS) studies were conducted to determine the coating stability and longevity. In-vitro hemocompatibility studies and HUVEC cell growth was performed to determine their thrombogenic and biocompatibility properties. Critical delamination load of the polymer coated Nitinol alloys was determined using Nano-scratch analysis. Sulforhodamine B (SRB) assays were performed to elucidate the effect of metal ions leached from Nitinol alloys on the viability of HUVEC cells. Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS), contact angle meter and X-ray diffraction (XRD) were used to characterize the surface of the alloys. MEP treated and polymer coated (PC) Nitinol alloys displayed a corrosion resistant polymer coating as compared to uncoated alloys. MEP and PC has resulted in reduced Ni and Cr ion leaching from NiTi5Cr and subsequently low cytotoxicity. Thrombogenicity tests revealed significantly less platelet adhesion and confluent endothelial cell growth on polymer coated and uncoated ternary MEP Nitinol alloys. Finally, this research addresses the bio and hemocompatibility of MEP + PC ternary Nitinol alloys that could be used to manufacture blood contacting devices such as stents and vascular implants which can lead to lower U.S. healthcare spending.