VictorJuiz/thesis huggingface dataset:
Optomechanical Dynamics in Vertical-Cavity Surface-Emitting Lasers

Vertical-cavity surface-emitting lasers (VCSELs) have emerged as one of the most numerous and diverse categories of semiconductor laser, serving applications in telecommunications, imaging, ranging, and sensing. Improving the behavior of these devices, while extending them into new application spaces, is currently one of the most active fields of optoelectronics research. Concurrently, improvements in micro-optics, micro-mechanics, and low-noise experimentation have produced a field of cavity optomechanics studying the forces of confined light to excite or cool mechanical systems. This thesis explores the interaction of those fields by observing optomechanical forces acting on the MEMS-supported high-contrast grating (HCG) reflector in VCSELs. The unique properties of the HCG as a lightweight, ultra-high-reflectivity mirror enable optomechanical forces to be more salient in these devices than in typical distributed Bragg reflector (DBR) VCSELs. Through optical, electrical, and microscopy characterization methods, we demonstrate the use of radiation pressure to drive the mirror through current modulation and self-oscillation, notably producing a large amplitude oscillation resulting in broad-spectrum self-swept light. By demonstrating optomechanical effects in a single device, we simplify the traditional cavity optomechanics experiment and open a new design space in which to obtain the ingredients necessary for feedback-based optomechanical damping. Looking to both the applications of passive cavity optomechanics and those of wavelength-swept VCSELs, we highlight applications for these phenomena and design and fabrication changes to further explore and harness optomechanical forces in VCSELs. Additionally, we show the development of the first physics-based compact model of VCSELs, which enables simultaneous design of VCSELs and circuits to enhance VCSELs’ performance in communications, ranging, and optomechanics.

Advisor: Chang-Hasnain, Constance J
Using Hybrid MOOCs to Improve Teachers’ Academic Discourse Practices

Curricular and demographic changes in our schools have created significant shifts in the instructional needs of our classrooms. Inservice professional development (PD) through Massive Open Online Courses (MOOCs) has been posed as a scalable approach to meet the professional needs our teachers need to respond to instructional challenges. But what we know about MOOC PD is limited by our lack of knowledge of how teachers respond to this online mode, and by the shifting of MOOCs from simply online modes to hybrids using face-to-face interaction. This study is a multiple, embedded case study of the professional learning of 7 teachers participating in a hybrid MOOC. The MOOC was a multidimensional and adaptive platform to introduce current practices of engagement, the information gap, and an increased attention to language for teaching instructional strategies to elementary level teachers to support students’ development of academic uses of English./nThe research questions focused on how teachers processed PD features emphasized in the MOOC across 3 time points using a socio-cultural theoretical frame of developing teacher expertise (Snow, Griffin & Burns, 2005). Data sources included interviews, observations, surveys, and participants’ work assignment submissions. Findings suggest that teacher expertise was a mediator variable in response to the PD content and modes of delivery./nThe findings from this study have implications in research, policy, and practice. At a research level, multiple measures support analysis of modal interactions across different settings. Policy implications include specific suggestions to strengthen the collaborative nature of the PD. Implications for practice include providing additional instruction to teachers beyond the MOOC. Moreover, there is a need to develop teacher capacity for scaffolding authentic instructional interactions within context and based on ongoing formative assessment.

Advisor: Pearson, P. David
Friesen, Amber
Strategic R&D Investment around Seasoned Equity Offerings: Evidence from High-Technology Industries

Focusing on high-technology issuers, this study provides new evidence that managers strategically overinvest in research and development (R&D) projects prior to seasoned equity offerings (SEOs). It corroborates the theoretical prediction that managers with short-term valuation pressure tend to overinvest in long-term projects to elevate investors’ growth expectations (Bebchuk and Stole, 1993). I find that issuers with more intensive pre-SEO R&D expenditures exhibit lower productivity in terms of innovative output and operating performance following offerings, which is a primary manifestation of overinvestment. Such issuers also have higher price run-ups prior to offerings and lower long-term stock returns thereafter, suggesting that investors initially overestimate the future benefits of R&D expenditures but are subsequently disappointed by their low productivity. In additional analysis, I document that analysts make higher long-term growth forecasts prior to offerings for R&D intensive issuers, whereas such issuers are more likely to miss analysts’ sales forecasts subsequently relative to non-intensive issuers. This evidence suggests that analysts fare no better than investors in correctly anticipating the future benefits of pre-SEO R&D expenditures. Further analysis of managers’ disclosure of the intended use of proceeds indicates that R&D intensive issuers tend to provide more non-financial R&D information to reinforce investors’ growth expectations. Finally, I provide evidence that the documented strategic R&D investment behavior among seasoned issuers is not explained by managerial overconfidence.

Advisor: Sloan, Richard G.
Dechow, Patricia M.
A Computational Study of Nanoporous Material used in Ions/Water Separation

In this thesis, the potential applications of typical nanoporous material (including Graphene Oxide (GO), Carbon Nanotube (CNT) and molybdenum disulfide (MoS_2)) in water and ion separation are systematically investigated. Different computational methods (including Molecular Dynamics (MD), Density functional theorem (DFT), Transport theorem in membrane) are introduced to study the mechanical and chemical properties of these materials; Depending on the corresponding experiments to be simulated, hundreds of models are built to explore properties in the process and compared with experimental results./nSeveral independent conclusions from different models are made and described in different chapters, whose main application is for desalination. Desalination is one of the most promising approaches to provide fresh water in the face of growing water demand. Currently, commercial reverse osmosis (RO) techniques still suffer from important drawbacks, including high energy consuming and serious fouling. In order for this method can be really used to solve the water challenges of this century, a step-change is needed in RO membrane technology. Because of significant advances in the field of nanotechnology and computational material and chemical science in the past decade, it is becoming possible to develop a new generation of RO membranes./nWe show that all these nanoporous materials possess exceptional physical and mechanical properties, which allow for water passage while rejecting salt ions if it possessed nanometer-sized pores. By using computer simulations (Both DFT and MD) from the atomic scale to the engineering scale, we first investigated the relationship between the atomic structure of nanoporous material and its membrane properties in RO applications. Then we studied the thermodynamics, chemistry and mechanics of each material and/nthe water and salt surrounding it. Finally, we establish the system-level implications of promising membrane properties for desalination plants, which can act as an RO membrane with several orders of magnitude higher water permeability than traditional polymer membranes as long as the size of nanopores is well controlled./nBesides of desalination, in chapter 6, we also investigate diffusion and selectivity of carbon nanotube embedded in the cell membrane to $Na^+$ and $K^+$ ions, in order to find the minimum diameter for different ions to pass through, and compare with the so called biological selectivity filters. The present work is a systematic study of ion and water transport through CNT embedded in cell membrane./nOverall, our efforts on this issue are of importance for future simulation studies investigating water and ion conduction through nanoscopic channels. This dissertation might also prove useful in designing more efficient nanoscopic conduits for future experimental studies, and even highlights a path for the development of next-generation membranes for clean water production in the 21st century.

Advisor: Li, Shaofan
The Bureaucratic Politics of Legal Reform: Chile as an Exceptional Case

This study is intended to gain a better understanding of the process of law-making in a presidentially-centric governmental structure, where the president holds legislative prerogatives. When a president retains and controls legislative priorities, participation in the making of laws is restricted to those actors who are close to the president or who hold positions of authority inside the executive. And in either case, to those whom they consult or invite to contribute, at their discretion./nDespite pervasive regional reform of immigration laws and policies in South America, Chile continues to regulate its own immigration with a statute that dates back to the now-discredited military junta of the 1970s and 1980s. This lack of reform in immigration law by Chile is puzzling considering Chilean reform and participation in a variety of other legal reforms which strengthened the country’s free trade, human rights commitments, strong civil society, and liberal political order./nUnlike what has happened in the liberal democracies of the North, immigration policies in Chile have emerged out of bureaucrats’ understandings about the role of the government in the management of immigration and their relative positions of authority and informal social connections inside the governmental structure. More specifically, high-ranking officials desire to maintain control over immigration law and policy, together with their hierarchical position inside the bureaucracy, have restricted mid-level bureaucrats’ attempts for comprehensive legal change at the presidential level. Change has occurred from the middle-out instead of the top-down. In the day-to-day implementation of policies, mid-level bureaucrats have created a reservoir of administrative practices, modifying the status quo and limiting top-officials’ reformist actions./nThe study builds on an in-depth, ethnographic case study of immigration policies in Chile developed between 2014 and 2016 during which time I spent twelve months acting as an active policy advisor to the Head of the Department of Immigration. I complemented my participant observation with 71 in-depth, semi-structured interviews with central and local public officials, congressional representatives, international organizations, pro-immigrants’ organizations, public interest lawyers, academics, and representatives from Chilean economic guilds. I further supplemented my fieldwork with evidence from official policy and legal documents and other secondary data.

Advisor: Morrill, Calvin
Effects of Corticotrophin Releasing Factor on Ventral Tegmental Area Neurons

A major hypothesis in the pathology of addiction is that maladaptive behaviors result from a disruption in the homeostatic balance between stress and reward circuitry. Several rodent models of stress (i.e. footshock, foot pinch, restraint stress, and social defeat stress) increase the activity of ventral tegmental area (VTA) neurons and result in an increase in dopamine in midbrain terminal regions. Corticotrophin releasing factor (CRF) is released in the VTA during stress and is reported to increase the firing rate of dopamine neurons, yet decrease dopamine release in the Nucleus Accumbens (NAc) (Wanat et al., 2008; Wanat et al., 2013; Wang et al., 2005). These results suggest that CRF differentially modulates discrete VTA circuits. However, the synaptic action of CRF on specific VTA circuits and its role in influencing behavior has yet to be characterized./nWe made ex vivo whole cell current clamp recordings to examine the synaptic actions of CRF. We measured responses to varying concentrations (100 nM to 1 mM) of CRF in both TH(+) and TH(-) neurons from throughout the VTA. To analyze circuit specific responses of CRF recordings were made in labeled neurons 7 days after the retrograde fluorescent marker DiI was injected into midbrain terminal regions including medial prefrontal cortex (mPFC), NAc, and amygdala. CRF consistently increased the firing rate of spontaneously active neurons. However, in quiescent neurons we observed both depolarizations and hyperpolarizations. Amygdala-projecting VTA neurons were consistently excited by CRF, whether firing spontaneously or quiescent. Given the importance of kappa opioids receptor (KOR) activation in the inhibition of dopaminergic neurons that project to the amygdala and PFC we also examined the possibility that CRF modulates KOR signaling in the VTA (Margolis et al., 2008). We used whole cell ex vivo electrophysiology and found that exposure to CRF can uncover a novel excitatory response to KOR activation in a subset of VTA neurons. These results provide insight into how stress may alter neuronal responses in VTA neuron populations.

Advisor: Fields, Howard L
Kriegsfeld, Lance
Understanding the Relationship of Pregnancy Weight and Weight Change with Infant and Child Health

Weight and weight change during pregnancy influence fetal growth and development and may have long-lasting effects on offspring health. Additionally, nearly half of women now begin pregnancy overweight or obese and a wide range of weight is gained and lost during and after pregnancy. In response to these concerns, the Institute of Medicine (IOM) revised its gestational weight gain recommendations in 2009 to include a specific, relatively narrow range of recommended gain for women with prepregnancy obesity. Unfortunately, limited scientific evidence and quantitative methods guided these recommendations. The IOM made several research recommendations, including that studies on the impact of gestational weight gain on a range of child outcomes be conducted in large, diverse populations, and that such studies address the extent to which optimal weight gain differs by maternal prepregnancy body mass index (BMI) and other maternal factors, including maternal race/ethnicity./nThis dissertation aims to address gaps in our understanding of how pregnancy weight and weight change are associated with child health. The first paper demonstrates two recently developed, quantitative approaches to studying gestational weight gain and determining optimal ranges of weight gain for minimal risk of preterm birth. It also informs whether weight gain recommendations should be tailored to maternal race/ethnicity, which has previously been suggested by the IOM. The second paper identifies longitudinal trajectories of maternal weight from prepregnancy through the postpartum period and assesses the relationship between maternal weight trajectories and offspring obesity in childhood. The third paper determines if maternal history of physical abuse in childhood is related to the risk of offspring overweight in childhood, and whether prepregnancy BMI and gestational weight gain play mediating roles in such an association./nThese dissertation papers together provide valuable information to help determine ranges of weight gain during pregnancy that minimize risk of adverse infant and child health outcomes. They also intend to stimulate further research to establish a scientific evidence base for creating effective interventions and clinical gestational weight gain guidelines. Promoting healthy weight and weight gain in pregnancy presents a potentially feasible and effective opportunity to improve infant and child health.

Advisor: Abrams, Barbara
Mechanisms of Large COPII-coated Procollagen I Carrier Formation

The coat protein complex II (COPII) mediates ER-to-Golgi transport in protein secretion. Genetic diseases affecting COPII function have demonstrated a requirement for COPII in secretion of bulky cargos, such as the 300-nm procollagen I (PC1), which is 5 times the diameter of an average COPII vesicle. Although large COPII vesicles were previously observed in cells overexpressing KLHL12, a substrate adaptor of the E3 ligase CUL3, the role of large COPII vesicles as PC1 transport carriers was not unambiguously demonstrated, and the mechanism of cargo packaging and vesicle enlargement required further elucidation./nThe research presented in this dissertation reports the existence of bona fide large COPII carriers of PC1 with evidence from multiple advanced microscopy techniques. By developing a cell-free COPII vesicle budding reaction, we demonstrated that the capture of PC1 into large COPII vesicles requires COPII proteins and the GTPase activity of the COPII subunit SAR1. This reaction was then used to show the co-packaging of PC1 with its cargo adaptor TANGO1 and the SAR1 nucleotide exchange factor (GEF) SEC12 into large COPII carriers. Coordinated cargo-sensing by TANGO1 and vesicle size regulation by SEC12 through its GEF activity was further shown to be important for PC1 secretion. In an independent effort to understand how the CUL3-KLHL12 complex regulates the size of COPII and PC1 secretion, we discovered that monoubiquitylation of SEC31A can inhibit its stimulatory effect on SAR1-GTP hydrolysis. Together, the study of two independent regulatory pathways revealed a converging mechanism on COPII size regulation by adjusting the local concentration of SAR1-GTP.

Advisor: Schekman, Randy
The Semantics of Kʷak̓ʷala Object Case

In this dissertation, I investigate factors underlying the distribution of object case in Kʷak̓ʷala, an endangered Northern Wakashan language of British Columbia, Canada. Kʷak̓ʷala has two types of objects, instrumental (=s) and accusative (=x̌). To account for their distribution, I develop a semantic theory of object case that is grounded in event structure. The first central claim of this theory is that instrumental case marks internal arguments which participate in initiating subevents (Co-initiators), while accusative case marks internal arguments which participate in non-initiating subevents (Non-initiators). Concomitantly, any internal argument which participates in both the initiating and non-initiating subevents of an event can undergo instrumental/accusative case alternation. The second central claim of this theory is that instrumental case adds semantic value, while accusative case is a meaningless default./nSupporting evidence for these claims comes from field data. On the one hand, object case realization is constrained by verb meaning, as shown by the existence of correlations between particular semantic verb classes and particular case frames. On the other hand, evidence that case realization is determined by event structure comes from data showing that modifying event structure affects case realization. Three types of event structure modification which license case alternation include the Direct Manipulation Alternation, the Caused Motion Alternation, and semantic incorporation with the affixal verb -(g)ila ‘make’. The event-structural basis of object case is also revealed in the vicinity of weak verbs (Ritter & Rosen 1996) where the semantic value of object case is communicated independently of lexical entailments./nThis analysis allows us to see how Kʷak̓ʷala’s object case system manifests a wider cross-linguistic tendency for languages to grammaticalize a link between object-encoding and event structure. I illustrate this by showing that Kʷak̓ʷala’s object case system is semantically the mirror image of the object case system in Finnish, in which the final bound of events is grammaticalized as an interpretable accusative case (Leino 1982, Heinämäki 1984, 1994, Kratzer 2004). Taking an even wider view, Kʷak̓ʷala fits squarely within the event-structural typology proposed in Ritter & Rosen (2000), where languages are divided according to whether they grammaticalize the initial or final bound of events. Kʷak̓ʷala’s object case system thereby fits into existing cross-linguistic patterns while also expanding our notions of what a possible case system looks like.

Advisor: Mikkelsen, Line H
Fundamental Processes in Combustion of Stratified Mixtures

Stratified combustion, combustion of fuel/air mixtures with temperature and/or mixture-composition stratification, is present in many combustion-related phenomena and applications such as forest wildfires, mining explosions, vessel ruptures, gas turbines, and reciprocating engines to name a few. A new generation of highly efficient internal combustion (IC) engines capable of satisfying stringent emission requirements, including modern direct-injection gasoline engines and gas turbines with lean premixed pre-vaporized (LPP) combustors, requires more comprehensive understanding and control of stratified combustion. Fundamentally, stratification of temperature or mixture composition affects a wide range of combustion characteristics such as flame speed, flammability, mode of combustion, instability, and others./nThis dissertation aims to identify, analyze and evaluate fundamental processes in the combustion of stratified mixtures, using theoretical analysis and advanced numerical simulation tools. ASURF-Parallel, a transient numerical solver of compressible reacting flow, is developed on the basis of the original A-SURF and exploited for stratified combustion simulations. A domain-decomposition parallelization scheme using Message Passing Interface (MPI) is developed and implemented in ASURF-Parallel to speed up the otherwise time-consuming numerical simulations. A significant speedup with the speed-up factor up to 10 is achieved on lab-scale servers./nEffects of stratification on flame speeds, lean flammability limit, and modes of combustion are numerically investigated and studied. For flame speeds, laminar flame speeds of stratified flames propagating from rich mixtures to lean mixtures are generally faster than those of the corresponding homogeneous flames, primarily due to the preferential diffusion of lighter species and radicals such as H2, H and OH, i.e., the chemical effect. The degree of enhancement in flame speeds can be correlated to the degree of stratification, leading to the development of a transient local stratification level (LSL) model which is able to determine the stratified flame speeds incorporating both chemical effect and memory effect. For lean flammability limits, the extension introduced by stratification is very weak due to reduced overall reactivity and reduced degree of stratification. For modes of combustion, different modes can be realized by specific reactivity gradients, regardless of the sources of such gradients. Pressure waves introduced by ignition in a closed chamber can also lead to different modes of reaction front propagation and end-gas combustion. A transient reactivity gradient method is proposed to identify the onset of detonation.

Advisor: Chen, Jyh-Yuan
Dibble, Robert W