VictorJuiz/thesis huggingface dataset:
The effect of in-situ ocean acidification on the community structure of marine invertebrates with a focus on the gastropod Columbella rustica

Laboratory experiments show that ocean acidification can be detrimental to the growth and calcification of many organisms at the species level. However, the effects of ocean acidification at the ecosystem-scale are less studied and harder to predict due to the diversity of responses of taxa. Areas with naturally high CO2 levels are becoming increasingly important in determining community level responses of ecosystems to ocean acidification. This study adds to previous work conducted along a natural acidification gradient caused by cool volcanic vents in Ischia, Italy. Researchers found an increase in tolerant crustacean taxa but were unable to separate this increase from habitat-dependent causes. To eliminate this confounding variable, benthic invertebrate communities were characterized using artificial substrate to standardize the habitat. The primary objective, to examine the processes underlying community reorganization of mobile invertebrates caused by ocean acidification, was achieved by sorting 18 samples collected along the gradient to the lowest taxonomic level possible. To assess the physiological consequences of acidification for the dominant gastropod species, the characteristics of the dominant gastropod in the system, Columbella rustica, were surveyed for differences in size, shell condition and shell and body weight between the ambient and low pH zones.
Our results highlight the differing responses of invertebrate taxa to ocean acidification, showing a general decrease in calcifying organisms at lower pH and an increase in those taxa that exhibit little to no calcification. When the habitat was held constant, the increasing abundance of crustacean taxa seen in previous studies at these vents (when the habitat varied with the pH) was not observed. These results suggest that the increased abundance of small crustacean grazers at extreme low pH reported in a previous study is likely associated with changes in the structural characteristics of the habitat and cannot be attributed to a direct benefit of low pH to these taxa. Preliminary results also indicate that calcifying gastropods can cope with increased acidity, but at a pH threshold, the snails lose their ability to cope with increasing acidity through adaptive mechanisms.

Keywords: Stanford Biology Department
Ischia Island Italy
Castello Aragonese
ocean acidification
Columbella rustica.
Thesis
Advisor: Micheli Fiorenza
Denny Mark
The effect of teacher qualifications on student achievement gains: evidence from the fundesola schools in Brazil, 1999-2003

It is recognized that teachers have a crucial role in improving learning outcomes. Because quality differs by teacher, their potential impact on student outcomes may also differ. However, measuring teacher quality and its influence on learning has been challenging in educational research. In this paper I explore the effect of teacher qualifications on the rate of learning in Mathematics and Portuguese in Brazil. Drawing on longitudinal data from the Fundo de Fortalecimento da Escola (FUNDESCOLA) program from 1999 to 2003 and using a dose-response analysis and a latent trait model, I conclude that teacher qualifications positively influence the pace of learning in Mathematics. However, results for Portuguese were not significant, which may indicate that subjects require different models of teacher effectiveness. Also, I find that students’ socioeconomic status does not enhance the effect of teacher qualifications on the pace of learning in Mathematics and Portuguese.

Keywords: teachers
teacher effectiveness
teacher qualifications
learning outcomes
student achievement
Brazil
Fundo de Fortalecimento da Escola
Stanford Graduate School of Education International Comparative Education
Thesis
The Effects of Relative Age on Early Childhood Academic Achievement: How They Differ Between Gender and Change Across Time

Gary Becker argues that a person should make investments in human capital as early as possible because he will thereby maximize the period over which the investment pays out. Also, the pay out period will be less discounted, and a person's opportunity cost of time is lowest when he is young. However, this theory does not provide much guidance on what is the optimal age to enroll children in formal education. At that point, there are two concerns: (i) whether the child is learning more at home than he would at school and (ii) whether his age relative to his peers is such that he would learn more given his aptitude. Relative age has recently become a controversial issue because some parents now deliberately enrolled their children a year after they are eligible to start school, in the hope of giving them a permanent learning advantage. This is known as redshirting. There is little robust quantitative evidence on how relative age affects learning and whether the effects differ by gender or parents' education. I examine how relative age affects achievement using the nationally representative ECLS-K longitudinal survey. Because relative age could be endogenous to parents' observations of their child's maturity, I construct instrumental variables for relative age based on state-level policies of kindergarten entrance age cut-off dates. I find that the relative age has a positive effect from kindergarten through grade five in reading and from kindergarten through grade eight in math. I find little evidence of the permanent effect for which redshirting families hope. The relative age effect is greater for females and for children whose parents are more educated. The latter result suggests that children with more educated parents learn more at home than do other children.

Keywords:  Department of Economics
Stanford Department of Economics
human capital investment
relative age effects
kindergarten entrance cutoff age policy
redshirting practice
early childhood academic achievement
Thesis
Advisor: Hoxby Caroline M.
The Efficacy of Booster Seat Laws in Reducing Injury and Mortality: Estimating the Effects on Children and Testing for Compensating Behavior

Motor vehicle accidents have been the leading cause of death for children and youth for decades. Booster seats are designed to better protect children four to eight years old in the event of an accident, and over the past decade, forty-seven states and the District of Columbia have passed laws mandating their use. In this paper I estimate the effect that booster seat laws have on reducing injury and mortality among five- to eight year-old children, using data from the WISQARS cause of death database for the years 1999 to 2007 as well as from FARS fatal crashes database from 1994 to 2009. In addition to estimating the direct effect on children, I also test for compensating behavior among older age groups, who may change their behavior due to the perception of diminished risk to their children while driving. My findings indicate that there is a nearly 25% decrease in mortality among six-year-olds covered by booster seat laws, but that there is no statistically significant effect on five-, seven-, or eight-year-old mortalities. I also find that there is evidence of compensating behavior among older drivers, and that the estimated total increase in deaths among older drivers exceeds the number of lives saved among children.

Keywords:  Department of Economics
Stanford Department of Economics
Peltzman effect
child safety restraint
KABCO scale
Thesis
Advisor: Bhattacharya Jayanta
The Veil of Communism: An Analysis of Lifespan, GDP per Capita, Human Capital, and Agricultural Productivity in Eastern Europe

There is a clear economic difference between the more economically-developed Western Europe and their poorer counterparts in Eastern Europe and central Asia. But what caused this economic divergence? How big of a role did communism play? If communism is responsible, through what economic mechanisms did it manage to hinder growth? This paper will look at GDP/capita, growth in GDP/capita, human capital, labor to land ratio, ratio of unskilled to skilled workers, growth in lifespan, average expenditure per student and variations in these outcomes in order to determine a more specific impact of communism. This paper finds not only that communism had a huge negative impact on growth, but that even though communism was completely gone from Europe by 1991; it still impacts the growth of former communist countries. Moreover, there seem to be 2 blocks of countries within the communist bloc: non-Soviet Central and Eastern Europe and Soviet Eastern Europe and Central Asia and these two regions behave very differently.

Keywords:  Department of Economics
communism
economic growth
GDP per capita
human capital
labor to land ratio
ratio of unskilled to skilled workers
lifespan
expenditure per student
Stanford Department of Economics
Thesis
Advisor: Manova Kalina
The War on Whooping Cough: The Impact of Prevalence Elasticity and State Policies on Vaccination Behavior

According the theory of prevalence elasticity of disease, the demand for preventative care (e.g. vaccination) against a disease increases with the prevalence of that disease. In light of this theory, I will look at pertussis incidence over the past three decades within the United States. Over this time period pertussis (also known as whooping cough) has increased in prevalence among certain age cohorts, particularly the adolescent cohort. This prevalence increase has been attributed by many to an antivaccine movement which created holes in vaccination coverage. In an attempt to curb these epidemics, states have instituted mandatory vaccination policies for school children entering preschool and kindergarten, and some states are also beginning to require a booster vaccine for entry to middle school. Since these policies target specific age cohorts, I look at pertussis prevalence and vaccination behavior amongst both the adolescent and infant age groups. Using three econometric methods, I identify the effects of prevalence elasticity, mandates, and the anti-vaccine movement on vaccination behavior, and draw policy recommendations from these empirical findings. I observe low prevalence elasticity, likely the result of the anti-vaccine movement, and therefore recommend a larger role for mandated vaccination.

Keywords:  Department of Economics
Prevalence elasticity
pertussis
vaccination
immunization
rational disease dynamics
Stanford Department of Economics
Thesis
Advisor: Bhattacharya Jay
T-helper cells regulate the formation and function of specialized dendritic cell subsets in inflamed tissue [electronic resource] : implications for multiple sclerosis

In multiple sclerosis and many other autoimmune diseases, activated T-helper (Th) cells colocalize with monocytes and dendritic cells (DC) in the inflamed tissue. Evidence suggests that these activated Th cells may be driving monocytes to differentiate into DC, but this phenomenon has not been explored in vivo. Using various methods of activating T-cells in vivo and the mouse model experimental autoimmune encephalomyelitis (EAE), we investigate how Th cells influence the function and phenotype of nearby monocytes. Using in vivo labeling of monocytes with a commercially available anti-CD209 antibody, we show that T-cell activation induces the rapid formation of monocyte-derived DC (Mo-DC) in lymph nodes. These T-cell driven Mo-DC are capable of robustly stimulating naïve T-cells, but induce little T-cell polarization. Surprisingly, TNF[alpha] but not GM-CSF was required for CD209+ Mo-DC formation after T-cell activation. These findings expand the range of signals capable of driving Mo-DC formation beyond known PAMPS and cytokines to include activated T-cells themselves. We also show that activated bulk Th cells or Th1, Th2 or Th17 subsets, when cultured with autologous monocytes in vitro, promote the formation of MHC II+, CD11b+, CD11c+ Mo-DC that we call DCTh. While all Th subsets tested induced the formation of DCTh, Th17 cells uniquely promoted the formation of IL-12/IL-23 producing Mo-DC with potent Th1 polarizing capacity that we call DCTh17. Further, Th cells isolated from the CNS of mice with Th17 driven EAE, drive robust formation of DCTh that produce IL-12 and polarize naive T-cells toward a Th1 phenotype. These results show that DCTh17 are critical in the interplay of Th17 and Th1 mediated responses in EAE and have implications for the treatment of MS.

Advisor: Engleman Edgar G. primary advisor. Thesis advisor
Contag Christopher H. advisor. Thesis advisor
Lee Peter advisor. Thesis advisor
Steinman Lawrence advisor. Thesis advisor
Theories and applications of the large deviation principles for the mean-field model and the conservation laws [electronic resource]

This thesis considers the theories and applications of the large deviation principles for two model problems: one is a mean-field model for systemic risk and the other one is a scalar conservation law. In the systemic risk problem, I prove that individual risk does not affect systemic risk in an obvious way; that is to say, low individual risk does not unconditionally lead to low systemic risk, and in fact, it is possible to construct a system with low individual risk and high systemic risk at the same time. The conservation law problem considers the anomalous shift of a traveling wave due to space-time random perturbations; it becomes a large deviation problem as the random perturbations are small. I prove that the rate function, the rate of the exponential decay of the probability, is quadratic in the amount of the shift of the wave when the amount of the shift is small, and is linear in the amount of the shift if the amount is large. A large-deviation-based importance sampling Monte Carlo method is also implemented to compute the probability of the anomalous shift, and the numerical experiments show that it outperforms the basic Monte Carlo method.

Advisor: Papanicolaou George primary advisor. Thesis advisor
Glynn Peter W. advisor. Thesis advisor
Iaccarino Gianluca advisor. Thesis advisor
Thermal and mechanical phenomena in aligned carbon nanotube films [electronic resource]

Efficient heat conduction is critical to the performance and reliability of a variety of devices. To ensure efficient heat removal from electronic devices, thermal interface materials (TIMs) are used to enhance heat conduction between two contacting surfaces. Ideal TIMs have high thermal conductivity, conform to the microscale roughness of the surfaces in contact, and accommodate stresses due to mismatch in thermal expansion coefficients. Commercial TIMs exhibit a tradeoff between these desired thermal and mechanical properties. Vertically aligned carbon nanotube (VACNT) films have great promise as TIMs because they have high through-plane thermal conductance and mechanical compliance. VACNT films are typically composed of a complex, entangled network of CNTs and the density and alignment of CNTs within a film affect its mechanical and thermal properties. Given the variety of growth techniques and variations in film morphology, it is important to understand how these factors influence film behavior. The present work combines three major aspects of VACNT film characterization: mechanical and thermal characterization, analysis of the film microstructure, and modeling of the film properties. The inhomogeneous VACNT film morphology is investigated by using image analysis to quantify CNT alignment and density and by measuring the elastic modulus at the top and bottom film surfaces using nanoindentation. The alignment and density information is input into a model of the mechanical response of the VACNT film, which is compared to measured data. The through-plane thermal properties of VACNT films are measured using thermoreflectance techniques. Multiwall VACNT films are grown directly on a thermoelectric material and the thermal properties of the films are characterized using nanosecond thermoreflectance. A set of eight single-wall VACNT films are measured using frequency domain thermoreflectance to extract four relevant thermal properties: thermal conductivity, heat capacity, and the upper and lower boundary resistances.

Keywords: Mechanical Engineering
Advisor: Goodson Kenneth E.
Cai Wei
Kenny Thomas William advisor. Thesis advisor
Thermal phenomena in nanostructured materials & devices [electronic resource]

Nanostructuring leads to unique material properties and combinations of properties not naturally available in bulk materials. The study of these properties is critical to improving the device performance and reliability for a range of applications including electronics, thermoelectrics, and nanophotonics. This work focuses on efforts to push the thermal conductivity of nanostructured materials to the extremes: the thermal conductivity of carbon nanotubes (CNT) and nanotube-based materials can exceed that of metals, while the introduction of nanoscale boundaries (e.g. nanoscale pores in silicon nanowires) yields extremely low thermal conductivity materials. Furthermore, this nanostructuring also leads to unique combinations of properties. Porous silicon nanowires are a step towards the desired electron-crystal, phonon-glass combination ideal for thermoelectric applications, while thermally-conductive, mechanically-compliant carbon nanotube films for promising for electronics packaging. This work first explores how the high axial thermal conductivity of carbon nanotubes can be leveraged effectively in thin film and composites through detailed understanding of the phonon transport and measurements of CNT-based films. This work then investigates how nanostructuring silicon significantly reduces the thermal conductivity through enhanced boundary scattering and the possibility of phononic crystal effects. Specifically, measurements of individual, porous silicon nanowires and arrays of silicon nanowires show significant reduction in the thermal conductivity compared to bulk silicon. A detailed model for reduced thermal conductivity due to phonon boundary scattering is developed in conjunction with measurements. Finally, this work also examines how the composition and annealing conditions impact both thermal transport and photoluminescence in silicon-rich silicon nitride films.

Keywords: Mechanical Engineering
Advisor: Goodson Kenneth E.
Vuckovic Jelena advisor. Thesis advisor
Zheng Xiaolin
Three compositions [electronic resource]

This portfolio comprises of three works composed over the course of the dissertation period. The first is called, "alluvium, " for alto flute, bass clarinet and cello. The second piece is a string quartet called "vertebrae." The final piece, "paralipomena, " is scored for a mixed ensemble of eight.

Keywords: Music
Advisor: Ferneyhough Brian
Chafe Chris advisor. Thesis advisor
Ulman Erik
Three essays on the data-driven analysis and modeling of public policy [electronic resource]

The goal of the research presented in this dissertation was to apply mathematical modeling and optimization techniques to the evaluation and improvement of public policies. This data-driven approach was applied to three studies. The first study examined the problem of child obesity. We built a stochastic model to describe the evolution of US children's Body Mass Index (BMI) under a treatment plan targeting children with a BMI exceeding a certain threshold. We solved the optimization problem of assigning thresholds at different ages to minimize the projected obesity-related disease prevalence at age 0$ with a constraint on the total screening cost. Using National Longitudinal Surveys data on US children's BMI development, we found that our optimal screening policy results in reduced projected obesity-related disease prevalences compared to the United States Preventive Services Task Force (USPSTF) recommendations. Furthermore, our results suggest that the optimal screening policy would be to focus on older adolescents, instead of screening children uniformly throughout earlier childhood. The second study evaluated the ballistic imaging systems that help solve crimes by comparing newly acquired images of cartridge casings or bullets to a database of images obtained from past crime scenes using data from the Israeli police force. Specifically, we incorporated time and spatial location of new images into our matching decisions. Inclusion of such extraneous information allows the matching to favor pairs of images closer together in space and time. Our results show an increase in the detection probability compared to the traditional approach. Moreover, we extend our model to the case of the US and show the potential of expanding regional ballistic matching programs to a national program. The third study focused on strategies for allocating ready-to-use therapeutic foods and ready-to-use supplementary foods to children in developing countries. Using a longitudinal data set from the Bwamanda region in DR Congo, we built a stochastic model to track each individual child's height-for-age z score (HAZ) and weight-for-height z score (WHZ) throughout the first five years of life. We identified a simple strategy of allocating the entire budget to therapeutic food for prioritized children based on a linear combination of one's HAZ, WHZ and age. The results reduced the mean number of disability-adjusted life years (DALYs) per child during 6 -- 60 months of age compared to a class of benchmark policies. The results of these three studies demonstrate that formulating public policy tradeoffs as constrained optimization problems can indeed yield improvements in effectiveness or reduction of costs. In particular, the application of such techniques in healthcare and law enforcement can lead to better understanding of the interplaying factors behind the policy in question and help policy makers to make more informed decisions.

Advisor: Wein Lawrence primary advisor. Thesis advisor
Goldhaber-Fiebert Jeremy D. advisor. Thesis advisor
Murray Walter advisor. Thesis advisor