VictorJuiz/thesis huggingface dataset:
Subsidies, infrastructure quality, and economic development [electronic resource]
Keywords: Economics

Electricity and water subsidies are an important form of social assistance in developing countries. However, households receive no direct benefit from such subsidies if they do not pay for their consumption of these services. Instead, the subsidies effectively become transfers from the government to the utility firms, creating an incentive for the firms to maximize the value of this subsidy payment. In Chapter 2 I provide evidence of such behavior by firms in a quantity-based electricity subsidy program for households in which consumption is unobserved. Using billing data and household characteristics, I show that unmetered households are billed for quantities that exceed any plausible estimate of their true, unobserved consumption. I estimate that this overbilling results in additional transfers from the government to the firm of nearly one sixth of total government expenditure on electricity subsidies. In Chapter 3 I develop an empirical framework to explain the persistence of unreliable infrastructure as the result of this targeted program of utility subsidies. I estimate a structural model of household demand for electricity, using customer billing data from Colombia matched to household characteristics and network outage data. I use this model to predict the change in consumption from upgrading households with low quality connections. Combining this with cost and regulatory data, I calculate the change in the utility firm's profits from the upgrade. I demonstrate that the existing program of targeted subsidies in Colombia deters investments to modernize infrastructure in areas with unreliable electricity supply. Households in these areas receive low quality service for which they do not pay, firms receive transfers from the government to tolerate areas with non-payment, and the government provides these transfers to prevent mass disconnections of non-payers. Based on the model estimates, I analyze less costly subsidy programs that provide stronger incentives for firms to upgrade neighborhoods with low-quality connections. In Chapter 4 I estimate a model of the household demand for electricity that includes both the short-run consumption decision, as in Chapter 3, and the long-run choice of the appliances that the household owns. I use a discrete factor approximation for the correlation between the unobserved components of the individual appliance choice and electricity consumption decisions. The reliability of electricity service enters demand directly through its effect on current-period consumption, and indirectly through its effect on the appliances owned by the household. I use the model to show that reliability improvements affect demand primarily through changes in the household's appliance portfolio.
Surface / interface characterization of thin film energy devices [electronic resource]
Keywords: Mechanical Engineering

Thin film devices for energy conversion have become a vital area of research to achieve high performance with low cost. As the surface-to-volume ratio becomes significant, the fundamental physics of the surface and interface microstructures and the reaction mechanisms are important to developing such energy devices or processes. My Ph.D. research is thus focus on surface and interface characterization of energy materials for thin film devices with engineered components fabricated by novel technologies. The first part of this dissertation discusses how surface microstructures influence fuel cell performance. According to the high resolution characterization of surface grain boundaries in solid oxide ion conductors, oxygen vacancy segregation at grain boundaries was observed, indicating that the grain boundaries can be more active sites for oxygen incorporation into the electrolyte. This preferred surface reaction at grain boundaries was verified by AC impedance spectroscopy. In addition, using atomic force microscopy, the local rearrangement of charged species on the oxide surface was investigated as a function of time and temperature to quantitatively analyze the diffusivity of oxygen vacancies on the surface. The second part discusses investigation of quantum confined structures that was aimed at contributing to the development of new solar cell architectures. The electronic properties of quantum confined structures, fabricated by atomic layer deposition (ALD), were characterized by scanning tunneling microscopy. In particular, the band gap of lead sulfide quantum well was tuned as a function of well thickness and potential barrier height. In addition, various nano-patterning techniques were developed to fabricate higher-order quantum confined structures, including area-selective ALD.
Surface plasmon enhanced photodetectors [electronic resource]
Keywords: Applied Physics

Photodetectors play an increasingly vital role in information technology, forming the basis of modern fiber-optic communication systems as well as digital imaging for consumer, medical, and scientific applications. Innovation in the design and fabrication of photodetectors has been a key enabler in the drastic reduction in size of digital cameras such that a five megapixel camera can now be embedded in a cell phone, as well as the scaling of fiber-optic networks from transcontinental networks spanning hundreds of kilometers down to local networks within a server room spanning several meters. However, further scaling is inhibited by the fundamental diffraction limit of classical optics, which limits the ability to make efficient optical components at the nanoscale. In this dissertation, our work on utilizing surface plasmon polaritons, coherent electron oscillations coupled to a photon and bound to a metal-dielectric interface, to make semiconductor photodetectors with sub-wavelength active regions well below the classical diffraction limit and the optical absorption depth of the semiconductor. We theoretically investigate plasmon enhanced photodetector designs using finite-difference frequency domain (FDFD) numerical simulations of Maxwell's equations. FDFD simulations are particularly well suited to modeling plasmonic devices because they can handle dispersive materials, such as metals, without approximation and adaptive grid spacing for structures with disparate length scales. FDFD simulations are used to characterize and optimize silicon photodetectors with integrated resonant plasmonic structures. By properly optimizing the resonant structures, near-field absorption in the silicon can be enhanced up to 350%, a phenomenon known as extraordinary optical absorption (EOA). We experimentally investigate these devices by fabricating resonant plasmonic nano-structures in aluminum and gold films on bulk silicon and silicon-on-insulator devices. We find good agreement with theoretically predicted properties, and experimentally measure absorption enhancements up to 300%. Finally, we investigate silicon detector devices integrated with deep sub-wavelength plasmonic waveguides. Such devices are promising for optical interconnects directly integrated with modern microprocessors.
Switched-capacitor DACs using open loop output drivers and digital predistortion [electronic resource]
Keywords: Electrical Engineering

High-speed communication systems, such as the 10 Gb/s Ethernet standard for copper cabling (10GBASE-T), use digital signal processing (DSP) to overcome the noise and bandwidth constraints of communication channels and, thereby, improve network throughput. The sophistication of these DSP techniques is possible because engineers can implement them using very little area and power in modern CMOS processes. And as CMOS technology scales, the power and area costs of digital logic become even more favorable. The requirements of communication systems also put pressure on circuit designers to develop higher-fidelity, higher-speed digital-to-analog converters (DACs). Unfortunately in this case, CMOS technology scaling offers a mixed bag of trends: some favorable to the most prevalent techniques used in DAC design and others unfavorable. The research presented in this dissertation is an attempt to let CMOS scaling trends guide the DAC design process. To this end, we have developed a new DAC architecture that relies on DSP to overcome some of the limitations encountered in analog and mixed signal design. The architecture consists of a digital predistortion block, a switched-capacitor DAC core, an open-loop output driver, a calibration ADC and a calibration algorithm. During normal operation, the predistortion block operates on the input data stream in such a way that nonlinearties in the DAC core and open-loop output driver are cancelled. Because these nonlinearities can change over time, the calibration ADC monitors the DAC output in the background, allowing the calibration algorithm to continuously update the predistortion coefficients. The predistortion block is implemented as a lookup table that re-maps each input sample to a unique internal value. This allows the predistorter to consume low power, but it also limits the kinds of errors that can be cancelled. Only memoryless nonlinearities, which are nonlinearities that are not a function of signal frequency, can be corrected. Existing DAC architectures are not good candidates for this kind of correction because their performance varies significantly across frequency. Therefore, the architecture that we have developed was designed so that its dominant nonlinearity mechanisms are approximately memoryless relative to the frequencies of interest. A 12-bit, 800-MS/s prototype chip demonstrating the new architecture was fabricated in a 90-nm CMOS process. The prototype achieves better than 58 dB SFDR for signal frequencies below 200 MHz and better than 53 dB SFDR for signal frequencies below 400 MHz. The full-scale output current is 16 mA, but by changing the resistive load seen by the DAC, we tested output voltage swings from 0.65 Vppd to 2.9 Vppd. We could discern no difference in SFDR performance for large or small output voltage swings.
The synaptic vesicle protein B0AT3 (SLC6A17) catalyzes sodium-coupled neutral amino acid transport [electronic resource]
Keywords: Neurosciences.

The SLC6 family of structurally related, Na+-dependent transporter proteins is responsible for presynaptic reuptake of the majority of neurotransmitters including dopamine, serotonin, norepinephrine, glycine, and GABA. Additional family members transport creatine, osmolytes, or amino acids, but several transporters remain orphans with unknown function. SLC6A17 is an orphan transporter in the SLC6 family that was first identified in the early 1990s. It is expressed exclusively in the nervous system and specifically on synaptic vesicles in glutamatergic and some GABAergic neurons. Despite extensive efforts by other research groups, no substrate or transport mechanism has been reported for SLC6A17. In this dissertation, I describe the functional characterization of SLC6A17 and discuss the potential physiological relevance of SLC6A17 as a synaptic vesicle protein. I show that endogenous and heterologous SLC6A17 localizes to vesicular populations in cultured rat hippocampal neurons and mammalian cell lines. I then use a combination of molecular manipulations to increase expression of the SLC6A17 protein at the plasma membrane and directly demonstrate that it catalyzes neutral amino acid transport. The transport characteristics of SLC6A17 resemble those of its closely related family member B0AT2 (SLC6A15). The substrate profile of the SLC6A17-dependent activity, similar to that of B0AT2, includes a sub-millimolar apparent affinity for proline and leucine and a low millimolar apparent affinity for glutamine. SLC6A17, like B0AT2, exhibits a Na+-dependent, Cl--independent transport activity that is inhibited at low pH. These similarities in substrate profile and transport mechanism suggest that SLC6A17 and B0AT2 have redundant roles, leading to our naming the SLC6A17 protein as B0AT3. Finally, I examine the pH sensitivity of B0AT3-mediated transport using live imaging techniques. My analysis suggests that B0AT3 and B0AT2 do not couple substrate movement with proton flux, supporting an uncoupled role for proton inhibition. This characterization of B0AT3 offers insights on neurotransmitter metabolism and also highlights mechanistic differences among the structurally related, but functionally divergent, SLC6 proteins.
Synchrotron X-ray scattering studies of anomalous oxygen order in superconducting mercury barium copper oxide and of charge-transfer excitations in related undoped lamellar copper oxides [electronic resource]
Keywords: Applied Physics

The first part of this Thesis describes the discovery, using diffuse X-ray scattering, of an unconventional interstitial-oxygen chain order in the model cuprate superconductor HgBa2CuO4+d. The oxygen order occurs within the Hg-O plane and the typical chain length is found to be about 25 unit cells. This order is unconventional, because of the observed high ordering temperature (around 800 K), the temperature-independent chain length, the weak associated lattice distortions, and the conservation of the global tetragonal symmetry of the crystal lattice. Moreover, the chains are observed only above a critical oxygen concentration, which coincides with the disappearance of a recently discovered novel magnetic order and the with the plateau anomaly on the underdoped side of the superconducting dome. One possible interpretation of the findings is that the appearance of the oxygen order is a manifestation of an underlying change in the electronic structure of the copper-oxygen planes. The second part of this Thesis describes experimental and theoretical Cu K-edge resonant inelastic X-ray scattering (RIXS) results for the charge-transfer excitations of several related undoped Mott insulators. First, in a study of Nd2CuO4, scattered-photon polarization effects are observed in the inelastic spectrum at the Brillouin-zone center. Raman selection rules accurately model these effects, which suggests that non-A1g charge-transfer excitations can be observed with RIXS. Next, the 1s4p electron-hole pair Coulomb scattering potential responsible for RIXS excitations at the Cu K-edge is calculated. While the strongest interaction is local and isotropic, non-local and anisotropic interactions are found to be sizable, and the formula for these Coulomb interactions is shown to follow selection rules which agree well with the observed scattered-photon polarization effects. In a separate experimental investigation, the momentum-dependent intensity of charge-transfer excitations of undoped cuprates is measured with RIXS, at the Cu K-edge. Reciprocal-space maps of the RIXS intensity at fixed energy show that the observed inelastic features are intrinsically broad and centered about high-symmetry points. Moreover, dispersion diagrams (constructed from energy scans collected along high-symmetry directions) show that these features correspond to distinct weakly-dispersing branches. Finally, a comparison of these branches for the compounds La2CuO4, Nd2CuO4, and Sr2CuO2Cl2 shows that the excitations constitute a universal set of features of the strongly-correlated electronic structure of the common copper-oxygen plane.
Synthesis and characterization of DNA-single molecule-DNA triblock structures [electronic resource] : as a novel approach towards single-molecule electronics
Keywords: Chemistry

A precise and reproducible electrical contact between a single molecule and the electrodes is the first step in studying single-molecule electronics, which uses individual molecules as active electronic components. One potentially promising strategy to make the electrical contact to a single molecule is to use DNA as a template. DNA has emerged as a good scaffold in the field of nanoelectronics because DNA is easily aligned over large areas, and can be employed as a conducting nanowire with micrometer-scaled length after metallization using metal ions. Moreover, oligodeoxynucleotide (ODN) can be readily linked to a single organic molecule, and its length can be further increased to several micrometer scales through DNA extension techniques. To build DNA-assist single-molecule device structures, I investigated the reactivity of ODN to synthesize organic molecule-bis(ODN) triblock oligomers through three separate cross-coupling routes, such as amide-coupling reaction, isothiourea-bond formation, and "click" chemistry. Specifically, the amide-coupling reaction is scrutinized to enhance its reactivity since it affords the highest yield among the cross-coupling reactions. The optimized amide-coupling reaction is also employed to incorporate functional organic molecules, involving a fluorophore and a conjugated polymer, into ODNs. Organic molecule-bis(ODN) triblock oligomers were characterized by denaturing gel electrophoresis and electrospray ionization mass spectrometry. The ODNs of the triblock oligomers are elongated by polymerase chain reaction (PCR) or DNA hybridization/ligation methods. PCR is a fast and precise method to construct organic molecule-bis(1.5 kbp dsDNA) triblock structures from the triblock oligomers. On the other hand, DNA hybridization/ligation affords longer length of the ODN using micrometer-sized DNA fragments, which are prepared from lambda DNA using restriction enzymes and a phosphatase. Thus, organic molecule-bis(micrometer-sized DNA) triblock structures are assembled to obtain fully stretched DNA strands. To characterize the triblock structures, fluorophore-bis(micrometer-sized DNA) triblock structure was synthesized through DNA hybridization/ligation, and then directly imaged by combined atomic force and single-molecule fluorescence microscopy. For the purpose of building a single-molecule transistor device, a conjugated polymer-bis(micrometer-sized DNA) triblock structure was metallized by palladium metal ion. The metallized triblock structure is characterized by scanning electron microscopy (SEM) to monitor a nanogap from the conjugated polymer (contour length: ~7 nm). Unfortunately, the nanogap is not observed, due to overgrowth of metal ions during the DNA metallization. To overcome the problem, I also describe the synthesis of a micrometer-sized DNA-conjugated polymer-gold nanoparticle asymmetric triblock structure.
System failure diagnosis for the advanced LIGO HAM chamber seismic isolation system [electronic resource]
Keywords: Aeronautics and Astronautics

The Laser Interferometer Gravitational Wave Observatory (LIGO) is a ground-based observatory which is designed to detect the gravitational waves radiated from accelerating massive objects in deep space. Currently, we are developing a new system which upgrades Initial LIGO to Advanced LIGO. However, in Advanced LIGO, the platforms, which hold the mirrors for the interferometer, contain many sensors and actuators. Thus, when the system is not running properly, the operator has to spend a lot of time in order to determine the component which causes the malfunction. Therefore, developing a method that can easily detect the malfunction of the system and help operators to determine where the malfunction comes from becomes an important issue.
Taking our country back? [electronic resource] : political consultants and the crafting of networked politics from Howard Dean to Barack Obama
Keywords: Communication.

While many scholars argue that the falling cost of producing and disseminating digital information drives new forms of collective political action, this dissertation reveals how digital tools, practices, and cultural processes together shape electoral campaigning. In the process, this research shows that digital technologies are not the primary drivers of changes in political practice and networked politics is not as radically democratic as many scholars suggest. Through open-ended interviews, archival research, and participant observation this work shows how until the 2003-2004 presidential election political consultants used the Internet as mass medium. During the Howard Dean campaign, however, consultants deployed a set of Internet applications that enabled citizens to work together on tasks such as voter mobilization and fundraising. As these new media staffers drew from their corporate experience to build these tools they described the campaign as a technologically-empowered, 1960s-style social movement. The dissertation concludes by showing how after the campaign these staffers founded political consultancies and brought these tools, techniques, and claims to many other sites in electoral politics, including Barack Obama's bid for the presidency. While telling this history, this dissertation shows how social formations and cultural work together shape the uptake of tools in electoral campaigning. Meanwhile, in contrast to many accounts of democratizing 'Web 2.0' technologies, this dissertation reveals that digital media vastly extend the power of campaign consultants to motivate, channel, and control electoral work.
Teaching and performance [electronic resource] : a study in two acts
Keywords: Education.

This dissertation explores the ways in which performance, as a way of knowing, a means of practice, and a mode of inquiry, characterizes the act/art of teaching. Drawing insights from cognitive neuroscience, analytic philosophy, and poststructuralist theory, act one advances a conception of "pedagogical performance" that challenges ongoing attempts by advocates of "scientifically based" education research to establish a "knowledge base" of teacher effectiveness. These chapters culminate in a case study of the political economy of teaching in Singapore, where a regime of Performance Management may be seen to control, albeit tenuously, the discourses of teacher professionalism through which teachers' performances are evaluated and legitimated. Act two comprises three separate but related chapters that examine social and cultural performances of literacy, identity, and oracy in virtual learning environments. Throughout, I experiment with "performative writing" as a mode of analysis, "data" representation, and reflexive critique. In sum, my dissertation proposes a modest but ambitious exploration of "performance" as an expansive paradigm for making sense of the complexities of teaching and learning, drawing on a rich body of interdisciplinary scholarship that has come under the inclusive banner of Performance Studies.