VictorJuiz/thesis huggingface dataset:
Bounds on the Entropy of a Binary System with Known Mean and Pairwise Constraints

Maximum entropy models are increasingly being used to describe the collective activity of neural populations with measured mean neural activities and pairwise correlations, but the full space of probability distributions consistent with these constraints has not been explored./nIn this dissertation, I provide lower and upper bounds on the entropy for both the minimum and maximum entropy distributions over binary units with any fixed set of mean values and pairwise correlations, and we construct distributions for several relevant cases./nSurprisingly, the minimum entropy solution has entropy scaling logarithmically with system size, unlike the possible linear behavior of the maximum entropy solution, for any set of first- and second-order statistics consistent with arbitrarily large systems./nI find the following bounds on the maximum and minimum entropies for fixed values of $\{\mu_i\}$ and $\{\nu_{ij}\}$./nFor the \emph{maximum entropy}:/n\begin{equation*}/nx N - \mathcal{O}(\log_2{N}) \leq S_2 \leq N./n\end{equation*}/nIn the case of uniform constraints, $x = 4(\mu - \nu)$ if $\nu \geq \nicefrac{1}{2}\,\mu$ and $\nu \geq \nicefrac{3}{2}\, \mu - \nicefrac{1}{2}$; otherwise $x = \frac{\nu - \mu^2}{\nicefrac{1}{4} - (\mu - \nu)}$./nFor the \emph{minimum entropy}:/n\begin{equation*}/n\log_2 \left( \frac{N}{1 + (N-1) \bar\alpha } \right) \leq \tilde{S}_2 \leq \log_2 \left( 1+\frac{N(N+1)}{2} \right),/n\end{equation*}/nwhere $\bar\alpha$ is the average of $\alpha_{ij} = (4\nu_{ij} - 2\mu_i - 2\mu_j + 1)^2$ over all $i,j \in \{1,\dots,N\}$, $i \neq j$./nPerhaps surprisingly, the scaling behavior of the minimum entropy does not depend on the details of the sets of constraint values --- for large systems the entropy floor does not contain tall peaks or deep valleys comparable to the scale of the maximum entropy./nI also demonstrate that some sets of low-order statistics can only be realized by small systems./nMy results show how only small amounts of randomness are needed to mimic low-order statistical properties of highly entropic distributions, and I discuss some applications for engineered and biological information transmission systems.

Advisor: DeWeese, Michael R
Safety and core design of large liquid-metal cooled fast breeder reactors

In light of the scientific evidence for changes in the climate caused by greenhouse-gas emissions from human activities, the world is in ever more desperate need of new, inexhaustible, safe and clean primary energy sources. A viable solution to this problem is the widespread adoption of nuclear breeder reactor technology. Innovative breeder reactor concepts using liquid-metal coolants such as sodium or lead will be able to utilize the waste produced by the current light water reactor fuel cycle to power the entire world for several centuries to come./nBreed & burn (B&B) type fast reactor cores can unlock the energy potential of readily available fertile material such as depleted uranium without the need for chemical reprocessing. Using B&B technology, nuclear waste generation, uranium mining needs and proliferation concerns can be greatly reduced, and after a transitional period, enrichment facilities may no longer be needed./nIn this dissertation, new passively operating safety systems for fast reactors cores are presented. New analysis and optimization methods for B&B core design have been developed, along with a comprehensive computer code that couples neutronics, thermal-hydraulics and structural mechanics and enables a completely automated and optimized fast reactor core design process. In addition, an experiment that expands the knowledge-base of corrosion issues of lead-based coolants in nuclear reactors was designed and built./nThe motivation behind the work presented in this thesis is to help facilitate the widespread adoption of safe and efficient fast reactor technology.

Advisor: Greenspan, Ehud
Minimally Actuated Dynamic Climbing in the Sagittal Plane

This thesis explores the design of systems that can climb vertical surfaces with non-negligible dynamics in the sagittal plane. The development of a low-dimensional model addresses a lack of understanding of sagittal plane dynamics during climbing in the space of reduced-order dynamic models of legged systems. Using a construction derived from the well-known and well-studied Spring-Loaded Inverted Pendulum (SLIP), we propose a two-legged system with both torsional and linear compliance driven by a position-controlled rotational actuator. Two simple foot models are considered to explore their effect on the dynamics and stability of the system. Results of the model indicate the existence of passively stable gaits during climbing as well as during inverted running and also suggest mechanical tuning parameters for physical climbing systems. A robotic platform capable of producing dynamic climbing behaviors is introduced. A reduced profile, sprawled posture, and improved internal mechanics allow the CLASH platform to be adapted to different climbing substrates. A passive claw engagement mechanism is proposed and tested with simulated steps to verify the design. With these mechanisms, CLASH becomes the first robotic platform capable of climbing loose cloth and climbs vertically at 15cm/s or 1.5 body-lengths per second. When climbing ferromagnetic surfaces, the system is capable of climbing at 1.8 body-lengths per second. To climb smooth, hard surfaces, a foot with a passively aligning ankle with a tendon-loaded gecko-inspired adhesive is designed and tested using simulated steps. With these engagement mechanisms, the system is able to climb at 1 body-length per second on acrylic with a 70-degree incline. A simple foot-impact model is created to explain the robot's inability to climb faster or up steeper inclines due to the sagittal plane reaction forces created during rapid running.

Advisor: Fearing, Ronald S
Directed Culture: The Spectator and Dialogues of Power in Early Soviet Theater

The theater played an essential role in the making of the Soviet system. Its sociological interest not only lies in how it reflected contemporary society and politics: the theater was an integral part of society and politics. As a preeminent institution in the social and cultural life of Moscow, the theater was central to transforming public consciousness from the time of 1905 Revolution. The analysis of a selected set of theatrical premieres from the Bolshevik Revolution in 1917 to the end of Cultural Revolution in 1932 examines the values, beliefs, and attitudes that defined Soviet culture and the revolutionary ethos. The stage contributed to creating, reproducing, and transforming the institutions of Soviet power by bearing on contemporary experience./nThe power of the dramatic theater issued from artistic conventions, the emotional impact of theatrical productions, and the extensive intertextuality between theatrical performances, the press, propaganda, politics, and social life. Reception studies of the theatrical premieres address the complex issue of the spectator's experience of meaning--and his role in the construction of meaning. The evolving historical context and the changing institutional foundations of theater altered the interpretive contexts of performance. The discussion of interpretive communities and audience tastes draws on reviews in the contemporary press and the data from theater surveys conducted during the 1920s./nThe theaters continually sought to align their aesthetics with the demands of the regime and the preferences of theatergoing publics. In addition, ideology served as a form of currency in the polemics among theater directors and theater critics who were engaged in the contest for dominance in the theater world. The theater spectator became a central ideological figure invoked by warring interpretive communities in these ongoing dialogues of power. The theater became politicized under Soviet rule; under Stalin it became a deformed expression of mass politics.

Advisor: Bonnell, Victoria E
The SHU:SH Project Slurs Hurt Us: Safety and Health - Lesbian, Gay, Bisexual, and Transgender Students at School

Teachers can be one of the most powerful factors in creating a safer school culture through intervening when they hear lesbian, gay, bisexual, and transgender (LGBT) slurs (Bockenek and Brown, 2001; Kosciw et al., 2009). Teachers are the primary adult contact students have throughout their school day, and many teachers hear gay slurs in the classroom and do not intervene. My design study focuses on creating a school culture where teachers intervene when they hear students using LGBT slurs in the classroom or on campus. This study does not focus on attempting to shift the entire school culture within the duration of the design study process but rather begin to acknowledge the critical LGBT issues on campus by addressing gay slurs. This design study is the beginning of a larger school culture change process./nThe SHU:SH Project Slurs Hurt Us: Safety and Health - Lesbian, Gay, Bisexual, and Transgender Students at School, a mixed-method study combining qualitative and quantitative methods, begins with identifying the problem of practice: students and teachers hear LGBT slurs on a daily basis in the classroom and hallways. What is problematic about this behavior is that teachers ignore these slurs, tolerate them, and do not intervene when they hear slurs. For this study, I developed a theory of action to guide the design. Drawing from the literature, I identified five key design elements in creating a professional development process by which a school culture is created to enable teachers and staff to intervene when they hear LGBT slurs on campus: create cognitive dissonance and awareness, develop a safe space for conversation and reduce fear and defensiveness while creating responsibility and personalization, acknowledge depth of problem and deepen insight, engage in inquiry cycle while creating action space, and efficacy./nOverall, I found the unpredictability of difficult, volatile, and complex human interactions around social status requires enormously capable leaders (Theoharis, 2007). The local context of silence pervasive in this social justice high school embodied the complexity of addressing slurs. My hope is the next design iteration will focus on self-critical inquiry for social justice leaders, examine the local context of silence, and analyze the effective implementation of theory to practice within social justice initiatives.

Advisor: Mintrop, Heinrich
Beyond "Thanks": Power as a Determinant of Gratitude

Research has compellingly shown that gratitude is important for both personal and relational well-being (e.g., Gordon, Impett, Kogan, Oveis, & Keltner, 2012; Wood, Joseph, & Maltby, 2008); however, little work has documented the factors that moderate the experience of gratitude. One important factor influencing the experience and expression of emotion is social power (Keltner, Gruenfeld, & Anderson, 2003). Low-power individuals are less likely to think, feel, and act in ways that are consistent with their own personality, attending instead to external cues such as social norms. Across four studies, I examined whether low-power individuals would be less likely to rely on their dispositional tendency to be grateful when responding to gratitude-inducing situations, which are governed by strong social norms. As hypothesized, dispositional gratitude and expected feelings of gratitude after receiving help from others were correlated for high- and neutral- but not low-power participants (Studies 1 & 2). That is, after receiving help, high-and neutral-power participants expected to feel grateful in line with their dispositional tendencies, but low-power participants did not. Study 3 replicated the findings of the first two studies using an actual gratitude-inducing situation in the laboratory. In Study 4, power also influenced the interpersonal transmission of gratitude such that low-power individuals were less accurate in transmitting feelings of gratitude to their romantic partners relative to high-power individuals. Across studies I measured and manipulated social power using a variety of methods (e.g., role playing, subtle priming) and examined lay beliefs as well as actual reports of gratitude in response to receiving benefits from others. Taken together, the results of these four studies provide evidence that power is an important factor that influences the experience of gratitude, with low power attenuating the link between disposition and emotion.

Advisor: Chen, Serena
Keltner, Dacher
Photon Echo Studies on Coherence Dynamics in the Photosynthetic Bacterial Reaction Center

Photosynthetic light harvesting begins with collecting ambient photons via excitation of pigment molecules. The sophisticated design of the pigment-protein complexes is based on the cooperative network among structural motifs of pigment molecules and amino acid residues in proteins to achieve the remarkable efficiency and speed in light harvesting./nThe insight from nature's photosynthetic nano-machinery can be translated to an optimal material design. The principle behind such inherent excitation energy transfer dynamics were revealed with the advance of the femtosecond laser technique. One of the examples is the quantum mechanical coherence excitation energy transfer observed by nonlinear photon echo technique./nThis dissertation presents the investigation of the bacterial reaction center complexes using electronic coherence photon echo spectroscopy. The study focused on elucidating the origin of the coherence signals and identifying quantum mechanical components relevant to the excitation energy transfer. Experimental variables affecting the coherence signals were explored for the excitation energy transfer of photosynthetic bacterial reaction center. The result showed that the vibrational coherence mimics the behavior of the electronic coherence, and the lifetime is near 2 ps. A mutant bacterial reaction center was also examined to confirm the vibrational contribution. A new polarization control experiment indicates that majority of the observed vibrational coherence is from the electronic ground state.

Advisor: Fleming, Graham R
The Development and Investigation of Cobalt Catalysts for the Chemical Transformations Related to Artificial Photosynthesis

Chapter 1. Small domains of cobalt on silica (CoSBA) were prepared by the reaction of Co[N(SiMe3)2]2 and SBA-15, resulting in a range of surface structures as the cobalt loading varied from 0.27 to 5.11 wt%. X-ray absorption spectroscopy (XAS) was employed to characterize these surface structures, which range from single-site cobalt atoms to small clusters of Co3O4. The CoSBA materials exhibit photochemical water oxidation catalysis, revealing distinct catalytic activities associated with characteristic types of surface structures that are dominant in particular concentration regimes. The catalytic turnover frequency for water oxidation of an isolated single-site cobalt atom (0.0143 s-1) is much greater than that observed for a surface atom of a small cluster Co3O4 on silica (0.0006 s-1). The CoSBA catalysts were recyclable for more than seven catalytic cycles (> 200 turnovers) with additional sacrificial oxidant, and no leaching of cobalt was observed. Post-catalytic analysis of CoSBA by XAS revealed that the cobalt atoms were partially oxidized to Co3+, without exhibiting significant surface migration and aggregation of cobalt atoms./nChapter 2. Single-site cobalt atoms on various oxide surfaces (TiO2, MgO, SBA-15, AlPO, and Y-Zeolite) were prepared and evaluated as water oxidation catalysts. Superior catalytic rates were observed for cobalt sites on basic supporting oxides (TiO2 and MgO) relative to those on acidic oxides (Y-Zeolite, AlPo, and SiO2). Per-atom turnover frequencies of ca. 0.04 s-1 were achieved, giving initial rates 100 times greater than a surface atom of a Co3O4 nanoparticle. No correlation was observed between catalytic rates and oxygen atom affinities of the supporting oxides./nChapter 3. Cobalt metaphosphate Co(PO3)2 nanoparticles are prepared via the thermolytic molecular precursor (TMP) method. A Ni foam electrode decorated with Co(PO3)2 nanoparticles is evaluated as an anode for water oxidation electrocatalysis in pH 6.4 phosphate-buffered water. Catalytic onset occurs at an overpotential of ca. 310 mV, which is 100 mV lower than that observed for Co3O4 nanoparticles, with a comparable surface area under identical conditions. A per-metal turnover frequency (TOF) of 0.10 - 0.21 s-1 is observed at η = 440 mV, which is comparable to the highest rate reported for a first-row metal heterogeneous catalyst. Post-catalytic characterization of the catalyst resting state by XPS and Raman spectroscopy reveals that surface rearrangement occurs, resulting in an oxide-like surface overlayer./nChapter 4. Linear trimetallic CoIII/CoII/CoIII cobalt complexes with bridging acyl-alkoxy ligands are electrocatalysts for the reduction of tosic acid in acetonitrile. The -OCMe2CH2COMe complex appears to operate homogeneously, and at an onset overpotential of only 25 mV. A turnover frequency of ca. 80 s-1 was observed at an overptotential of 150 mV.

Advisor: Tilley, T. Don
I. Direct C-H Functionalizations for the Synthesis of Nitrogen Heterocycles II. Approaches to the Synthesis of Dimeric Resveratrol-Derived Natural Products

The efficient synthesis of organic molecules hinges on the development of concise synthetic strategies. Sequences of chemical reactions can be rendered shorter by employing cascade processes, which accomplish multiple bond formations in a single operation. The direct functionalization of C-H groups with carbon or heteroatom groups offers an additional platform for streamlining synthesis by circumventing the need for an additional pre-functionalization step. This work describes the development of two direct functionalization methods (Chapters 1 and 2), as well as a cascade approach to a family of natural products (Chapter 3)./nAn overview of intramolecular C(sp3)-H amination is presented in Chapter 1. Recent approaches to C(sp3)-N bond construction are described and categorized according to the nature of the required precursors. First, C(sp3)-H amination methods that require substrates containing electron-withdrawing substituents on the nitrogen coupling partner are examined. Next, a C(sp3)-H amination method that relies on the oxidation of C,N-dianions generated from N,N-dialkylamines and benzylic carbon groups is discussed./nThe alkylation of pyridines and pyridine derivatives is examined in Chapter 2. The direct functionalization of pyridine derivatives is described and the challenges associated with direct C(6) alkylation of picolines are outlined. The direct C(6) alkylation of pyridyl alcohols using alkyl lithium reagents was developed after the initial observation that, when heated to 110 °C in toluene, n-butyl lithium adds selectively to the C(6) position of the pyridyl alcohol derived from cycloheptenopyridine. The substrate scope and reagent scope were investigated. Mechanistic studies of the direct alkylation of pyridyl alcohols were performed./nDimeric natural products derived from resveratrol are described in Chapter 3. Synthetic studies on resveratrol-based natural products are summarized and an overview of a previous synthetic strategy towards this family of natural products is presented. A palladium-catalyzed domino reaction was developed as part of a synthetic strategy to access dimeric resveratrol-derived natural products. The domino process involved sequential Heck-type coupling reactions and provided access to the benzofulvene-based core of various resveratrol-derived natural products. A related approach was applied to the synthesis of the natural product pauciflorol F.

Advisor: Sarpong, Richmond
Embryonic and Adult Stem Cells Explored through Microfluidics and Biological Manipulation

Part I - A Microfluidic Method for the Selection of Undifferentiated Human Embryonic Stem Cells and in Situ Analysis/nConventional cell-sorting methods such as FACS or MACS can suffer from certain shortcomings such as lengthy sample preparation time, cell modification through antibody labeling, and exposure to high shear forces or metallic microparticles. In light of these drawbacks, we have recently developed a novel, label-free, microfluidic platform that can not only sort cells with minimal sample preparation but also enable analysis of cells in situ. In contrast to MACS or FACS, cells sorted by our method have very high viability (~90%). In this part of my thesis, I first describe existing antibody-functionalized microfluidic devices for cell sorting as well those designed for human embryonic stem cell (hESC) sorting. I then demonstrate the utility of our platform to sort undifferentiated human embryonic stem cells (hESCs) from a heterogeneous population, achieving ~60% average purity of the cells expressing a marker of interest. I also discuss future strategies to improve sorting efficiency. Overall, our platform technology could be applied to other cell types beyond hESCs and to a variety of heterogeneous cell populations./nPart II - Attenuation of TGF-β Signaling via Incorporation of a Dominant-negative TGF-β Type II Receptor Promotes Improved Muscle Regeneration in Murine Skeletal Myoblasts/nSkeletal muscle stem cells known as satellite cells are responsible for muscle regeneration. Upon muscle injury or exercise, quiescent satellite cells become activated, proliferate as myogenic precursors, differentiate into myoblasts, and ultimately fuse into new, multinucleated myofibers. Unfortunately, this paradigm breaks down with aging and multiple factors contribute to a build-up of scar tissue instead of new muscle. Among these negative contributors are some members of the TGF-β family of signaling molecules. After an introduction to muscle regeneration and satellite cells, the adult skeletal muscle stem cells, I will discuss how biomaterials can help improve muscle regeneration and recent advances in combating TGF-β-induced impairment in muscle repair. I will then discuss the work I have done in improving skeletal muscle repair by attenuating the effects of TGF-β signaling via incorporation of a dominant-negative TGF-β type II receptor.

Advisor: Sohn, Lydia L
Conboy, Irina M