VictorJuiz/thesis huggingface dataset:
Templated sol-gel deposition and titanium dioxide nanoframe dye-sensitized solar cells [electronic resource]
Keywords: Electrical Engineering

Dye-sensitized Solar Cells (DSCs) have become a popular research topic because of their low-cost, high-efficiency solar energy conversion. While nanoparticle cell is currently the most efficient and stable DSC, nanowire cells have shown some significant advantage that would make them superior to nanoparticle cells. One such advantage is the fast and direct electron transport, which was reported to be several hundred times faster than trap-limited diffusion in nanoparticle cells, which can lower device efficiency caused by electron-hole recombination. The efficiency of current nanowire cells is primarily limited by the insufficiency of their internal surface area due to the mechanical weakness of nanowire structures. One solution to strengthen the nanowire structure is to build a framework where individual nanowires are connected and prevented from clustering, so as to increase the internal surface area and the efficiency of the solar cell. Nanoframes containing 20nm diameter TiO2 nanowire arrays were synthesized with polymer templates via cathodic Sol-Gel deposition followed by 450oC sintering. Dye-sensitized Solar Cells based on this nanoframe were fabricated and the effects of the top cover in the nanoframe, which is the only difference between nanoframe cells and nanowire cells, were investigated. The results show that the top cover does not prevent the I- and I3- ions underneath from diffusing freely in the electrolyte and causes no deterioration of the cell performance. The nanoframe cell is a promising device in which nanowire arrays are strengthened and the effective internal surface area have the potentiality to be increased without sacrificing the advantages of nanowire cell compared to nanoparticle cell.
Testing merger and acquisition sensitivity to changes in firm resources [electronic resource]
Keywords: Economics

This dissertation adapts a model of market discipline developed by Zweibel (1994) to describe how managers should use internal resources in the market for mergers and acquisitions. Prior literature, namely Harford (1999), has argued that additional cash on hand leads firms to undertake further merger activity. This paper argues that a more careful examination of the data demonstrates that this pattern does not hold in the data and also offers a simple model to explain why exogenous increases in a firm's cash holdings should not lead a manager to spend more money on either mergers and acquisitions or on capital expenditure, if both are viewed as wasteful or value decreasing spending at the margin. This dissertation adapts Rauh's (2005) use of pension funding status to identify exogenous changes in the level of cash holdings and then uses a Tobit model to test whether or not additional cash holdings leads firms to accumulate more capital or spend more on mergers and acquisitions. This dissertation finds that having more exogenous cash on hand does not lead to more merger and acquisitions spending or capital expenditure. The marginal expenditure on mergers and acquisition activity in also calculated as part of the study. Whether one uses instruments or not, the marginal expenditure is very small, suggesting that firms do not waste a significant amount of resources on merger and acquisition activity on the margin. This finding also suggests that stock price responses to merger and acquisitions announcements must be due to the dilution of shareholders value, revelation of a manager's characteristics, or some other factor besides the loss of a firm's assets.
Tetramers reveal CD4+ T cells that are specific for U1-70 in systemic lupus erythematosus [electronic resource]
Keywords: Immunology.

Antigen-specific CD4+ T cells have been implicated in the autoimmune disease systemic lupus erythematosus (SLE), yet little is known about the function of these T cells or the precise peptide antigens that they recognize. We hypothesized that antigen-specific CD4+ T cells contribute to lupus pathology through two mechanisms: (1) by providing help to B cells for pathogenic autoantibody production, and (2) by directly promoting inflammation through the secretion of proinflammatory cytokines. We tested these two hypotheses by generating a series of MHC class II tetramers of I-Ek containing peptides from the spliceosomal protein U1-70. These tetramers specifically stained distinct CD4+ T cell populations in MRL/lpr mice. Using these reagents, we demonstrated that CD4+ T cells specific for U1-70 (131-150):I-Ek correlated with disease and with anti-U1-70 autoantibody production, expressed ROR[lowercase gamma]t and Tbet, and produced IFN[lowercase gamma] and IL-17A in an I-Ek-dependent manner. We confirmed our findings from mice in human patients with SLE and mixed connective tissue disease (MCTD). U1-70 specific CD4+ T cells obtained from peripheral blood mononuclear cells (PBMCs) of patients with SLE produced IFN[lowercase gamma] in all 5 patients tested and IL-17A in 1 out of 2 patients whose serum contained RNP autoantibodies. These data support the hypotheses that antigen-specific T cells recognize the same autoantigens as B cells, and that they produce proinflammatory cytokines. These studies represent the first reported tetramers for studying antigen-specific T cells in a mouse model of lupus, and demonstrate an antigen-specific source of IL-17A in human autoimmune disease.
The Business Cycle's Secondary Effects on the Decision to Participate in the Food Stamps Program
Keywords:  Department of Economics
Stanford Department of Economics
United States
Food Stamps Program
participation
Consumer Expenditure Survey
electronic benefit transfer
Thesis

From January 2007 to July 2009, the number of participants in the United States Food Stamps Program (FSP) increased by 38%. Most analyses discussing this large participation increase attribute it to the recession that began in December 2007. However, existing literature has failed to explore how the recession increases participation. Specifically, there is no evidence as to whether the increase was caused entirely by decreases in income and assets or whether there were also secondary effects from changes in information, stigma, and transactions costs. This paper uses Consumer Expenditure Survey data from January 1993 to March 2009 to estimate the extent of these secondary effects. The paper also identifies the percent of the secondary effects that consist of changes in external stigma costs, by recognizing that the introduction of electronic benefit transfer (EBT) substantially decreased FSP external stigma costs. I find that a 1% point increase in the unemployment rate increases participation in FSP through secondary effects by 3.3% points. 87.5% of this effect is due to changes in external stigma costs. Further work is needed to examine the heterogeneity and the decomposition of these secondary effects, and the extent of these secondary effects on other welfare programs.
The Economic Lives of the Microfinanced Poor
Keywords:  Department of Economics
Stanford Department of Economics
Microfinance
BRAC
Poverty
Thesis

This paper uses a household survey conducted with 107 women in Mukono, Uganda receiving microcredit from BRAC, a globally renowned Microfinance Institution. Firstly, I aim to quantify differences between the residents of the district and the recipients of microcredit. Secondly, I will present descriptive analysis of the economic lifestyles of the BRAC respondents. Finally, I will analyze the relationship between length of membership and loan size with income and savings. I found that the differences between the Mukono population and the BRAC sample are particularly pronounced in methods of income generation and education. While 49% of the Mukono population is involved in subsistence agriculture, only 2% of the BRAC respondents are engaged in the activity. The data also revealed that the average BRAC respondent has attained a much higher level of education than that of the average Mukono resident. With an average of 8.8 years of education, the majority of the BRAC respondents finished schooling between primary and secondary level. By contrast, the majority of the Mukono residents did not complete the primary level. This assessment shows that BRAC’s targeted population is very different from the general population. While BRAC claims to alleviate poverty-related issues by providing financial services to the extremely poor, the poorest of the poor are not eligible to receive microcredit.
The Effect of Parents' Locus of Control Belief and Education on Investment in Their Children's Health
Keywords:  Department of Economics
Stanford Department of Economics
preventive care
external and internal outlooks
perceived control
guardians
Thesis

This paper investigates how parents’ locus of control beliefs affect investment in their children’s health, depending on parental education. Parents with an external locus of control attribute outcomes to external factors outside of personal control whereas internal parents attribute outcomes to personal actions. Because locus of control influences the perceived probability of investment returns, external parents may underestimate returns and under-invest. I develop an economic model that illustrates how locus of control affects perceived probability of returns, which has opposing effects depending on the level of parental education. With cross-sectional data on parents’ beliefs and health utilization, I examine the link between parents’ locus of control beliefs and child health investments for parents with low and high levels of education. Using a probit analysis and controlling for income and insurance, I found a significant interaction effect between locus of control and education on the likelihood of children obtaining regular checkups. Educated parents with internal beliefs invest more in their children’s health than their counterparts. There are also trends that educated, internal parents are less likely to disinvest in health by smoking and binge drinking, but the effects are insignificant. Results confirm my theoretical model that locus of control affects health investments differently for low and highly educated parents, but not for health disinvestments. This research has important policy implication because changing parents’ beliefs and promoting education on the importance of health investment could be a cost-effective intervention to advocate for optimal health investment.
The Effect of Price Control Threats on Pharmaceutical R&D Investments
Keywords:  Department of Economics
Stanford Department of Economics
drug reimportation
R&amp;D
pharmaceutical
Thesis

This study examines how pharmaceutical R&D was impacted by two threats of price controls: Clinton's Health Security Act of 1993 and Clinton's signing of drug reimportation legislation in 2000. Firms with higher fraction of U.S. sales decreased their research intensity relative to firms with mainly foreign sales following the 1993 threat, but not the 2000 threat. Additionally, brandname pharmaceutical firms, characterized by large R&D expenditures decreased their R&D efforts post 1993 threat relative to firms that did not engage in as much innovative R&D.
The Effect of Skewed Sex Ratios on Marriage Markets in India
Keywords:  Department of Economics
Stanford Department of Economics
marriage market
Haryana
sex ratio
bargaining power
India
assortative matching
Thesis

This paper will explore how the declining sex ratio in Haryana, a state in north India, has affected the local marriage market. The ratio of the number of women to men has been falling over time, due to the strong preference for sons and prevalence of sex-selective abortion in this region. Studies show that lower sex ratios lead to higher female bargaining power, but I empirically show that there has been no change in female bargaining power in the region surveyed. I argue that the relative shortage of women causes a squeeze in the marriage market, which has two potential consequences: (i) an increasing age difference between spouses and (ii) an increased geographical spread of the marriage market. I test these hypotheses using primary data collected from households in three districts in Haryana. I conclude that the declining sex ratio has no effect on spousal age gap, but does increase the distance traveled by wives for marriage. This could explain the unresponsiveness of female bargaining power to the sex ratio change, since the marriage market is simply expanding geographically to compensate for the shortage of women rather than by directly altering intra-household dynamics.
The Effects of Performance-Based Teacher Pay on Student Achievement
Keywords:  Department of Economics
Stanford Department of Economics
teacher pay
performance-based pay
synthetic control matching
Thesis

I evaluate the effects on student achievement of the Teacher Advancement Program (TAP), a school-level intervention that offers teachers professional development resources and performance-based compensation. Because TAP typically targets low-performing schools, assignment to the intervention is nonrandom. I use synthetic control matching methods to circumvent this selection bias. I then use a difference-in-differences model to estimate the effects of TAP on state achievement exam scores in reading and mathematics. I find that students in TAP schools outperform students in comparison schools by roughly one-fifth of a standard deviation in mathematics. I find mixed results in reading.
The Relationship Between Social Service Provision, Militancy, and Violence: Egypt in the 1990s
Keywords: Center for International Security and Cooperation
CISAC
Egypt
terrorism
social services
childhood vaccinations
Thesis

This study explored the relationship between social service provision and a community’s involvement in terrorism. I used Egypt as a case study to statistically examine whether communities with a greater proportion of fully vaccinated children produced per capita fewer terrorists.
Using The Global Terrorism Database to examine violence between 1990 and 1997 and The Demographic and Health Survey conducted in 1995, I found that, in general, communities with a greater proportion of fully vaccinated children produced fewer terrorists per capita than communities with lower vaccination rates. While demonstrating the correlation between vaccination level and attack rate, I also discovered that terrorists generally preferred to attack close to home, with over fifty percent of attacks occurring within fifty miles of a perpetrator’s hometown.
I examined four Egyptian provinces that represented different combinations of social service provision, and observed the level of violence in each province. While I discovered interesting correlations in three of the provinces, anomalies in the fourth suggested, in this limited sample size at least, that although social services can reduce levels of violence, it would be foolish for any government to believe that simply servicing a region could be preventive against terrorist attacks, since violence can arise from a number of factors.
The Stanford Diverging Cusped Field Thruster: Design, Construction, and Initial Testing
Keywords: Burchat, Patricia
diverging cusped field thruster
Thesis

The design and initial characterization of a cylindrical diverging cusped field (DCF) thruster is presented. The thruster operates with krypton propellant at power levels ranging from 25-250 W. Thrust, specific impulse, and thrust (anode) efficiency are found to be very sensitive to cathode placement, and thrust efficiencies exceeding 20% are found over a range of operating conditions. The discharge current shows that this thruster is quiet, displaying none of the periodic oscillations seen in typical Hall thrusters. Plume ion current measurements indicate the existence of a conical ion emission, similar to that seen previously in a model with diverging channel walls; this suggests that the ion divergence of the plume is more closely connected to the magnetic field topography than the channel geometry.
When operating with 300 V to the anode, plasma potential measurements throughout the near-field reveal regions of elevated plasma potential (in some places exceeding 100 V) that are coincident with the most luminous visible regions of the discharge and peaks in ion current density. Channel potential measurements show that a significant potential increase (from 12% to 88% of anode potential) occurs within a few millimeters around the exit plane, also corresponding to a bright visible plasma region. Electron temperature is shown to peak along the thruster axis (in some areas over 10 eV).
Preliminary results of a kinetic electron simulation based on experimental potential data are also presented. The high magnetic field strengths cause electrons to move in tight helical orbits and undergo several mirroring events. Thus far, test electrons released in the near-field fail to reach the channel, while test electrons released along the thruster axis remain confined to the channel, sometimes reaching the anode.
The Withering Sword? Explaining the 21st Century Decline in Japanese Military Expenditures
Keywords: Stanford University
Center for International Security and Cooperation
Japan
foreign policy
military expenditures
Thesis

In light of a changing security context in the past two decades, Japan has taken several steps towards a more military-oriented foreign policy, especially through a high number of peacekeeping operations and contributions to the war efforts led by the United States in Afghanistan and Iraq. Despite moves in the direction of a foreign policy in line with realist expectations, Japan’s military expenditures have actually been diminishing since 2002. While some scholars continue to assert that Japan is in fact remilitarizing, its declining defense budget in fact translates into a waning military capability that could undermine its rising international military activities. This paper seeks to answer the question: why has Japan been curtailing its military spending and capabilities in the context of a rising threat environment? To unravel this puzzle, this paper analyzes the decline in military expenditures through three different theoretical lenses—alliance theory, domestic politics, and bureaucratic politics. This paper concludes that a bureaucratic politics model best accounts for the observed decline. The forces pressing for fiscal restraint in the bureaucratic bargaining process, embodied by the Ministry of Finance and the Cabinet Office, gained leverage in the bargaining process once their interests became aligned in 2001. The rise to power of Koizumi, and even more significantly the creation of the Council of Economic and Fiscal Policy facilitated the change of direction seen in the budget. Finally, the last chapter of this thesis explores the policy implications of this paper’s findings for the future of Japanese security policy, particularly in the context of the newly elected DPJ government.
Thermal characterization and modeling of nanostructured materials [electronic resource]
Keywords: Mechanical Engineering

Thermal conduction resistances are becoming increasingly complicated as advanced materials, photonics, and electronic devices incorporate more nanostructured features (e.g. carbon nanotubes (CNTs), ultra-thin films, nanoparticles, etc.). The reduced dimensions and large interface densities of nanostructured materials modify the energy transport physics, requiring the development of new thermal models and thermal metrology techniques with deep sub-micron spatial resolution. This research develops and applies ultra-fast (nanosecond thermoreflectance (TR) and picosecond time-domain thermoreflectance (TDTR)) to characterize thermal resistances in carbon nanotube arrays and thin-film materials. In conjunction, this work develops novel models of thermal transport within the nanostructured material and interfaces. Owing to their high intrinsic thermal conductivities (~3000 W/m/K), aligned arrays of CNTs are promising for use in advanced thermal interface materials. Nanosecond TR data for metal-coated aligned nanotube films show that the thermal resistance of the films is dominated by interfaces due to incomplete CNT-metal contact, and that the thermal resistance of these films can be significantly reduced by varying the metallic composition at the interface. This work presents data for the growth-interface thermal resistance of multiwalled carbon nanotubes measured directly using TDTR with a variable modulation frequency technique. The abrupt changes in geometry at nanostructured interfaces induce phonon confinement, which creates additional contributions to the interface resistance. This work investigates model problems of thermal transport through abrupt junctions between a one-dimensional lattice in contact with a two- and three-dimensional lattice using a Green's function approach. The model indicates that the thermal resistances due to dimensional mismatch are comparable to those due to material property mismatch effects. Finally, the results suggest that engineering an intentional impedance mismatch at a nanostructured interface may enhance the transmission of energy. This work also develops a picoseconds pump/probe thermoreflectance system to achieve deep sub-micron spatial resolution of thermal properties of ultra thin hafnium oxide films, which are promising for the next generation of gate oxides for transistors. These data isolate the intrinsic film resistance and show that crystalline nanoparticles reduce the intrinsic thermal conductivity its bulk value.
Thermal phenomena in phase change memory [electronic resource]
Keywords: Mechanical Engineering

Information storage and accessibility form the foundation of many modern electronic systems. High speed nonvolatile memory (NVM) technologies retain data without consuming power, driving the rapid growth of the portable consumer electronics market. Phase change memory (PCM) is an emerging NVM offering exceptional speed, storage density, and cycling endurance. This work uses novel multiphysics models to quantify the importance of thermal phenomena in PCM. It extends optical thermometry techniques to resolve the thermal transport physics critical for device functionality. Fully coupled finite element calculations capture the electrothermal and phase change processes in a confined cell device. The simulations demonstrate the critical role thermal boundary resistance (TBR) plays in reducing programming current. This result suggests that interface engineering can significantly reduce programming current. Compact electrothermal models use reduced cell geometries to accurately predict scaling in a variety of device geometries. These models demonstrate that the distribution of thermal resistances is the key design parameter for reducing the programming current. Nanosecond transient thermoreflectance (TTR) measurements on a variety of chalcogenide stoichiometries show that the effective thermal conductivity depends primarily on the material phase. This work extends nanosecond TTR up to 340°C to measure the thickness and temperature dependent effective thermal conductivity of GeSbTe (2:2:5) (GST) in the as-deposited, fcc, and hcp phases. Process dependent material defects, partial crystallization, and TBR all significantly alter the effective thermal conductivity. Picosecond time-domain thermoreflectance (TDTR) measurements establish the Al/TiN TBR, TiN/fcc GST TBR, and intrinsic fcc GST thermal conductivity up to 325°C. An original multi-sample, thickness-implicit data extraction technique uniquely separates the spatial distribution of thermal properties. The intrinsic conductivity increases slowly with temperature, consistent with materials with high defect and vacancy concentrations. The TiN/fcc GST TBR dominates the device thermal resistance and is the key factor determining the programming current.