VictorJuiz/thesis huggingface dataset:
Nonlinear Light-Matter Interactions in Metamaterials

Metamaterials possess extraordinary linear optical properties never observed in natural materials such as a negative refractive index, enabling exciting applications such as super resolution imaging and cloaking. In this thesis, we explore the equally extraordinary nonlinear properties of metamaterials. Nonlinear optics, the study of light-matter interactions where the optical fields are strong enough to change material properties, has fundamental importance to physics, chemistry, and material science as a non-destructive probe of material properties and has important technological applications such as entangled photon generation and frequency conversion. Due to their ability to manipulate both linear and nonlinear light matter interactions through sub-wavelength structuring, metamaterials are a promising direction for both fundamental and applied nonlinear optics research./nWe perform the first experiments on nonlinear propagation in bulk zero and negative index optical metamaterials and demonstrate that a zero index material can phase match four wave mixing processes in ways not possible in finite index materials. In addition, we demonstrate the ability of nonlinear scattering theory to describe the geometry dependence of second and third harmonic generation in plasmonic nanostructures. As an application of nonlinear metamaterials, we propose a phase matching technique called "resonant phase matching" to increase the gain and bandwidth of Josephson junction traveling wave parametric amplifers. With collaborators, we demonstrate a best in class amplifier for superconducting qubit readout - over 20 dB gain with near quantum limited noise performance with a bandwidth and dynamic range an order of magnitude larger than alternative devices. In conclusion, we have demonstrated several ways in which nonlinear metamaterials surpass their natural counterparts. We look forward to the future of the field where nonlinear and quantum metamaterials will enable further new physics and new applications.

Advisor: Zhang, Xiang
Wang, Feng
Design of Reconfigurable Radio Front-Ends

Modern and future mobile devices must support increasingly more wireless standards and bands. Currently, multi-band coexistence is enabled by a network of discrete, off-chip components that are bulky, expensive, and narrowband. As transceivers are required to accommodate an increasing number of wireless bands, the required number of discrete components increases accordingly, resulting in greater bill of materials (BoM) cost and front-end module (FEM) area. This work focuses on design techniques to enable front-end integration and reconfigurability in multi-band radios./nIn the first part of this work, we present a wideband spectrum sensing receiver with high sensitivity, wide dynamic range, and low power overhead. Reconfigurability in multi-band radios requires environmental awareness, and spectrum sensing can be used for optimal channel selection and adaptive interference suppression. The 300MHz-700MHz spectrum sensing receiver uses subsampling downconversion and digital-analog hybrid correlation to achieve -104dBm sensitivity and 84dB dynamic range for a 6MHz channel while consuming only 28mW of power. In the second part of this work, we present a wideband time division duplex (TDD) front-end with an innovative transmit/receive (T/R) switching scheme. T/R switches conventionally are off-chip components, and existing integrated designs have been narrowband or high loss. We propose a wideband integrated T/R switching technique in which the PA is re-used as an LNA during receive mode, and we demonstrate this in a 20dBm polar transmitter that can be re-purposed into a 3.4GHz-5.4GHz LNA achieving -6.7dBm P1dB and 5.1dB NF. The two systems presented in this thesis contribute key innovations towards fundamental aspects of future reconfigurable radios - greater front-end integration, wideband transceiver design, and spectrum awareness.

Advisor: Nikolic, Borivoje
Going Beyond the Provided Curriculum: Teachers’ Investigations of Outside Mathematics Materials

Elementary school teachers in the United States are typically provided curricular materials by their school districts. However, little is known about how teachers may replace or supplement these provided materials with outside materials—materials found in their own curricular libraries or from external sources. This dissertation proposes a research framework on teachers’ use of outside materials that leads to the following research questions: What motivates teachers to consider using outside curricular materials? What approaches do they use to discover outside materials? What criteria do they use to evaluate outside materials? What steps do they take to prepare or adapt outside materials? And what external factors relate to teachers’ decisions to use outside materials? These questions were addressed through an online survey of 98 elementary teachers across two districts in Western Washington state, interviews with nine survey respondents who frequently considered using outside materials, and in-depth case studies of the decisions of three interviewees. The survey revealed that a large majority of teachers considered using outside curricular materials at least once in the 2015-2016 school year, that many of them did so frequently, and that their reasons for considering outside materials were linked to areas of dissatisfaction with the provided materials. A multiple linear regression found that higher teacher-reported feelings of curricular autonomy and more years of experience with their provided curriculum predicted higher frequency of considering outside materials. The survey also revealed that teachers used a wide variety of approaches to discover outside materials, including both online and offline methods. Interviews provided detail to these findings, revealing that teachers’ evaluation criteria were aligned with their initial motivation to consider outside materials, and that teachers tended to engage in minimal preparation of outside materials. Case studies of three focal teachers were used to illustrate different motivations for considering outside materials and different approaches for discovery, as well as to elaborate and refine the research framework that guided this investigation. This dissertation adds to literature showing that teachers actively participate with curricular materials in order to reach their professional goals, and makes a strong case for including attention to outside materials in curriculum development, district-level decisions, and future research.

Advisor: Saxe, Geoffrey
Localized States in Driven Dissipative Systems with Time-Periodic Modulation

The generalized Swift--Hohenberg equation is used to study the persistence and decay of localized patterns in the presence of time-periodic parametric forcing in one and two dimensions. A localized state that was stable with constant forcing may begin to breathe under periodic forcing, i.e. grow for part of the forcing cycle via nucleation of new wavelengths of the pattern followed by wavelength annihilation during another part of the cycle. The breathing dynamics occur as the forcing parameter exits the region of stability of the localized pattern on either side and the fronts that define the edges of the state temporarily depin. The parameters of the forcing determine if there will be net growth, a balance, or net decay on average./nA novel resonance phenomenon between the forcing period and the time required to nucleate one wavelength of the pattern outside the pinning region is identified. The resonances generate distinct regions in parameter space characterized by the net number of wavelengths gained or lost in one forcing cycle. Canard trajectories, in which the localized state follows an unstable solution branch for some amount of time before quickly jumping to a stable one, appear near the transitions between each region. In one dimension, the partitioning of the parameter space is well described by an asymptotic theory based on the wavelength nucleation/annihilation time near the boundaries of the region of stability. This theory leads to predictions that are qualitatively correct and, in some cases, provide quantitative agreement with numerical simulations./nThe underlying resonance mechanism is a more general phenomenon and is also studied in the context of coupled oscillator systems with a periodically modulated Adler equation as a simple model. A strikingly similar partitioning of the parameter space is observed, with the resonances occurring this time between the period of the frequency modulation and the time for the generation of a phase slip.

Advisor: Knobloch, Edgar
After New India: Diasporas, Anglophonisms, Returns

After New India is a literary and cultural study of the Anglophone discourse on the rise of a “New India” after the economic liberalization of the country in the early 1990s. The project asks whether India’s putatively “global” ascendance has, in fact, as both popular and critical sources aver, decentered expatriate writers and exhausted diasporic tropes that were central to the writing and study of Indian Anglophone literature as “postcolonial” literature. In order to pursue this question, I focus on the contemporary literary registration of three aspects of India’s rise that map onto my sub-titular terms, “diasporas, Anglophonisms, returns”: first, the epochal, but ultimately counterfactual, temporal inversion in which India begins to represent world futurity vis-à-vis its diasporas in the West; second, the literary-critical discourse on the simultaneous globalization and indigenization of Indian English; and third, the empirical social fact of reverse migration to India, specifically by Indian Anglophone writers from the United States and United Kingdom. In readings of global icons, fictions, and nonfictions that have been central to the New India discourse, After New India shows how New India emerged through “East-East” encounters between diasporic and national figures of the Indian Anglosphere, who pursued their fellow Indians as proxies and informants in both real and narrative time. In so doing, the project argues that the rise of New India—a rise that inspired returns from diaspora to the nation—merits a critical return to diaspora as well./nThe three chapters of this project consider how the New Indian icons of the expatriate writer and the call center agent, national and diasporic novels by Chetan Bhagat, Bharati Mukherjee, and Raj Kamal Jha, and popular, nonfictional narratives of Indian ascendance written by diasporic repatriates including Suketu Mehta and Amit Chaudhuri differently mediate intersubjective encounters in the New Indian Anglosphere. Together, my readings show how longstanding worries about the illegitimacy of a colonially-bequeathed Indian English underlie the literary-critical turn away from postcolonial tropes (chapter one), novelistic preoccupations with call center English and the wordless subaltern (chapter two), and the repatriation of Indian writers seeking compensatory identification with their New Indian Others (chapter three). All of these movements can be understood as attempts to resolve the problem of diasporic Anglophonism in India through the “East-East” encounter. Ironically, After New India argues, they also evince the vitality of the diasporic vantage and significant transformations within Indian Englishes, plural, that render moot the assumption of Anglophone exceptionality. The Conclusion turns to the graphic novels of Sarnath Banerjee in order to offer a final word on the aspiration of self-return and a speculative account of the promise of India’s “redevelopment” after New India.

Advisor: Jackson, Shannon
Lye, Colleen
The Embryonic Origins of Primate Encephalization

Encephalization is one of the defining characteristics of the primate Order. Unlike other mammalian radiations, primates exhibit exceptionally high relative brain sizes at birth and across prenatal development. This indicates that the shared degree of adult encephalization in primates is the developmental product of changes to early brain or body growth that have never been fully characterized. This dissertation examines brain and body growth relationships across prenatal ontogeny in a wide range of primate and non-primate mammals in order to reexamine the developmental origins of primate relative brain size./nA review of allometric brain/body growth over fetal development shows that primate prenatal encephalization is shared by all primate radiations but not the closest out-groups, and begins during embryonic development. Fetal rates of exponential brain growth acceleration in primates are within the range of eutherian values; species with larger adult brains or isocortical proportions do not exhibit faster fetal brain growth. Neither allometric nor acceleration data support theories proposing faster fetal brain growth in mammals according to physiological or life history variables. Rates of fetal body and visceral organ growth acceleration are exceptionally slow in primates, consistent with slow postnatal body growth rates and life history schedules. Embryonic development is characterized by high brain/body proportions in many non-primate mammals; however, only primates retain this high allometric proportion into later fetal stages of development. This novel feature of primate growth is likely a consequence of slower post-cranial body growth, rather than any particular feature of primate brain growth and development./nThis study provides developmental evidence that increases in relative brain size at the origin of the primate Order may have been a consequence of body size reduction, possibly as an adaptation to locomotion within an arboreal niche.

Advisor: Deacon, Terrence W
Deliberative Democracy as Reflexive Social Inquiry

Two overarching questions motivate this dissertation: How might the participants to a nominally democratic process themselves craft decision-making processes that are “inclusive,” or, that best approximate the ideal of treating them and those, if any, they represent as “free and equal”? And what role, if any, might a normative theory of the democratic process play in their diverse efforts to do so?/nTo address these questions, the dissertation juxtaposes selected aspects of the literature on “deliberative democracy” with ideas drawn from pragmatist approaches to ethics and social inquiry. Broadly speaking, pragmatists theorize by explicitly drawing on the resources provided to us by our actual practices, and by making reference to the consequences they have for actual lives. The dissertation deploys pragmatist ideas to develop a normative theory of the democratic process, intended as a contribution to a public philosophy for contemporary democratic governance. In developing the theory, the dissertation illustrates how engaged, situated agents might invoke that theory in their diverse efforts to craft processes for collective decision-making that actually treat the citizens of the respective demos, or the members of the respective association, as “free and equal.”/nIn brief, the theory developed in this dissertation is a “deliberative” conception because, like other such conceptions, it stresses that democracy’s participants ought to try to justify their expressed policy preferences to one another. Yet, for a number of reasons, it is also distinct from other deliberative conceptions. For instance, it is distinctive in the stress it places on inquiry of various kinds. Indeed, the theory developed here suggests that, ideally speaking, democracy itself ought to be conducted as a form of collective social inquiry, one in which participants inquire into the procedures, virtues, and cultural practices that, in some particular context, are most apt to treat citizens or members in a way that is consistent with the values that arguably justify the adoption of a democratic process in the first place.

Advisor: Bevir, Mark
A Finely Tuned Molecular Motor: Mechanochemistry and Power Efficiency in the AAA+ Protease Machine ClpXP

Molecular motors transduce chemical energy –usually from ATP hydrolysis– into directed motion and mechanical work, which is used to perform key functions in almost every cellular process. Molecular motors are particularly important in the maintenance of cellular proteostasis, i.e. the equilibrium between protein synthesis and degradation. ATP-dependent proteases of the AAA+ family, such as ClpXP from Escherichia coli and the eukaryotic 26S proteasome, play a central role in protein degradation. Given its extensive biochemical and structural characterization, ClpXP is a paradigm for the study of the operating principles of eukaryotic and prokaryotic protease machines of the AAA+ family. However, the molecular mechanism by which ClpXP couples the energy from ATP hydrolysis into mechanical work is still poorly understood. Here we used biochemical and single-molecule assays with optical tweezers to directly probe the operation of ClpXP as it unfolds and translocates its protein substrate./nChapter one provides an introduction into the structure and function of ClpXP, which is considered an archetype for the study of AAA+ proteases. This chapter also introduces key concepts about single molecule studies assays with optical tweezers./nChapter two focuses on the study of the mechanisms of force generation and intersubunit coordination of ClpXP. We establish that ClpXP translocates its substrate by using cycles of alternating dwell/burst phases. Phosphate release is the force generating step in the ATP cycle, and ClpXP translocates its substrate in bursts resulting from highly coordinated conformational changes in two to four ATPase subunits. Based on our results, we propose a model where ClpXP must use its maximum firing capacity of four subunits to unfold stable substrates like GFP. Interestingly, the average dwell duration between individual bursts of translocation is constant, regardless of the number of translocating subunits, implying a constant translocation cycle governed by an unidentified “internal clock”. Together, our results indicate that ClpXP operates with constant “rpm” but uses different “gears”./nChapter three describes the complete mechanochemical cycle of ClpXP, as well as the coupling and power efficiency of the motor. We show that ADP release and ATP binding happen non-sequentially during the dwell, while ATP hydrolysis and phosphate release occur during the burst. ADP release is the rate-limiting transition of the ATP cycle. Interestingly, the size of the highly-conserved translocating loops within the ClpX pore has been evolutionarily optimized to maximize motor power generation, as well as the coupling between chemical and mechanical cycles of the motor. Finally, we presente evidence showing that the conformational resetting of these loops between consecutive bursts seems to determine ADP release from individual ATPase subunits and the overall duration of the motor’s cycle, which explains the observed “internal-clock mechanism” of ClpXP.

Advisor: Bustamante, Carlos J
Bio-inspired problems in rate-distortion theory

Designed and evolved sensors are faced with a difficult optimization problem: storing more information about the environment and reaping greater “rewards” costs time, energy, and material. Quantifying the ben- efits and costs associated with storing environmental information will aid design of more efficient sensors and allow other researchers to test whether or not a particular biosensor is, in fact, efficient. One principled approach to this quantification comes from rate-distortion theory. We discuss three biologically inspired problems in rate-distortion theory. First, we validate a new approach to perceptually compressing natural image patches; sec- ond, we show that sensing tradeoffs in large fluctuating environments depend only on coarse environmental statistics; and third, we describe a new method for calculating predictive features and memory-prediction trade- offs in stochastic environments. For the last of these problems, we suggest a new class of stimuli that might be used to profitably test whether a par- ticular biosensor is an efficient predictor of its environment.

Advisor: DeWeese, Michael R
Molecular Dynamics Modeling of PPTA Crystals in Aramid Fibers

In this work, molecular dynamics modeling is used to study the mechanical/nproperties of PPTA crystallites, which are the fundamental microstructural/nbuilding blocks of polymer aramid fibers such as Kevlar. Particular focus is/ngiven to constant strain rate axial loading simulations of PPTA crystallites,/nwhich is motivated by the rate-dependent mechanical properties observed in/nsome experiments with aramid fibers. In order to accommodate the covalent/nbond rupture that occurs in loading a crystallite to failure, the reactive/nbond order force field ReaxFF is employed to conduct the simulations./nTwo major topics are addressed: The first is the general behavior of PPTA/ncrystallites under strain rate loading. Constant strain rate loading/nsimulations of crystalline PPTA reveal that the crystal failure strain/nincreases with increasing strain rate, while the modulus is not affected by/nthe strain rate. Increasing temperature lowers both the modulus and the/nfailure strain. The simulations also identify the C--N bond connecting the/naromatic rings as weakest primary bond along/nthe backbone of the PPTA chain. The effect of chain-end defects on PPTA/nmicromechanics is explored, and it is found that the presence of a chain-end/ndefect transfers load to the adjacent chains in the hydrogen-bonded sheet in/nwhich the defect resides, but does not influence the behavior of any other/nchains in the crystal. Chain-end defects are found to lower the strength of/nthe crystal when clustered together, inducing bond failure via stress/nconcentrations arising from the load transfer to bonds in adjacent chains near/nthe defect site. The second topic addressed is the nature of primary and/nsecondary bond failure in crystalline PPTA. Failure of both types of bonds is/nfound to be stochastic in nature and driven by thermal fluctuations of the/nbonds within the crystal. A model is proposed which uses reliability theory/nto model bonds under constant strain rate loading as components with/ntime-dependent failure rate functions. The model is shown to work well for/npredicting the onset of primary backbone bond failure, as well as the onset of/nsecondary bond failure via chain slippage for the case of isolated/nnon-interacting chain-end defects.

Advisor: Papadopoulos, Panayiotis