VictorJuiz/thesis huggingface dataset:
Palladium and platinum complexes for the oxidation of small molecules [electronic resource]
Keywords: Chemistry

Palladium is a versatile metal used prominently in synthesis. The rapid growth of palladium oxidation chemistry in the past decade has spurred a number of new processes that allow for the selective oxidation of substrates under mild conditions. This growth, specifically in the field of aerobic alcohol oxidation, attracted our attention, with the hope that it would provide new catalysts for use in direct methanol fuel cells. Toward that goal we developed a new cationic palladium complex, [(neocuproine)Pd(OAc)]2[OTf]2, which shows unprecedented initial turnover frequencies for aerobic alcohol oxidation at room temperature. However, catalyst lifetimes are limited due to the generation of reactive partially reduced oxygen species that promote oxidation of the ligand and deactivation of the catalyst. The use of milder oxidant like benzoquinone extended catalyst lifetimes prompting a further exploration of the substrate scope. Oxidation of glycerol proceeds exclusively at the secondary alcohol to yield dihydroxyacetone. Other 1,2-diols also favors oxidation of the secondary alcohol. Methanol oxidation proceeds at a much slower rate, but yields methyl formate with selectivities greater than 90 %. The mechanism for this process was probed through the use of model studies and isotopic labels suggesting the transient generation and oxidation of methyl hemiformal. In a parallel effort toward the extension of catalyst lifetimes, a number of new oxidatively resistant ligands were synthesized and used toward the formation of palladium catalysts that exhibit extended catalyst lifetimes. Additional efforts have focused on the use of similar catalyst for the oxidative carbonylation of 1,2- and 1,3-diols to yield 5-membered and 6-membered cyclic carbonates in the presence of N-chlorosuccinimide, iodosylbenzene, or dichloroisocyanuric acid. Finally, a new platinum dimer containing a trimethylplatinum unit and bridging amides was synthesized and characterized. Its reactivity toward the reductive elimination of ethane of methanol derivatives was explored. Additional work with known platinum dimers suggests these species, upon addition of silver triflate, facilitates the C-H activation of a number of unactivated arenes and promotes the C-H functionalization of propargyl aryl ethers.
Paradigm and discourse in archaic greek poetry [electronic resource]
Keywords: Classics

This dissertation is a study in the style of paradeigmata ([Greek word omitted], mytho- logical exempla, exemplary tales) in Archaic Greek poetry and wisdom discourse. Part One comprises two corpus-based studies of Homeric poetry in terms of three linguistic features (discourse markers, relative clauses, and register); each of these studies is fol- lowed by a comparative study in Hesiodic poetry. Here I suggest that genealogical cata- logue poetry known from the Hesiodic tradition is an important traditional resource for these narratives. Part Two makes an analogous study of non-hexameter poetry from the Archaic Period as well as wisdom discourse attributed to Aesop and the Seven Sages. In these chapters I emphasize two strategies in particular: the creation and 'mythologization' of authoritative personae, and the sociocultural import of the stylistic features of ge- nealogical catalogue in select Pindaric odes. Drawing on the findings of Part One and Part Two, the two studies in Part Three present readings of the Iliad and Odyssey through an analysis of how the linguistic features and themes of paradeigmata work at the level of poetic composition.
Parallel stochastic particle methods using Markov Chain random walks [electronic resource]
Keywords: Aeronautics and Astronautics

Particle methods, also known as Monte Carlo methods in the statistical community, have become a powerful tool for a variety of research areas such as chemistry, astronomy, and finance, to list a few. This is mainly due to the enormous advances in computational resources in recent years. In this work, we consider an efficient and robust parallel methodology that can be applied to particle methods in a general setting. The parallel methodology proposed in this thesis takes advantage of Markov Chain random walks and corresponding Markov chain theory. We develop parallel stochastic particle methods in two different areas: (1) the optimal filtering problem, and (2) simulation of particle coagulation. In each application, a mathematical proof of convergence as well as a numerical example are provided. After a brief review of Markov Chain random walks and an explanation of the two application areas, the Markov Chain Distributed Particle Filter (MCDPF) algorithm is introduced. The performance of this method is demonstrated with a bearing-only-measurement target-tracking numerical example and is further compared with an existing method, the Distributed Extended Kalman Filter (DEKF), using a flocking model for the target vehicles. We study the convergence of MCDPF to the Centralized Particle Filter (CPF) and the optimal filtering solution by using results from Markov chain theory. In addition, the robustness of the MCDPF method is highlighted for practical problems. As the second application area, we developed a parallel stochastic particle method for the stochastic simulation of Smoluchowski's coagulation equation. This equation is used in many broad areas and for high-dimensional problems the stochastic particle solution is more accurate, stable and computationally cheaper than classical numerical integration schemes. In this application, simulated particles can be considered as representing physical particles. Since more particles result in more accurate and useful solutions, it is desirable to simulate this equation with a greater number of particles. By applying the parallel stochastic particle method, a comparable solution is obtained more efficiently using multiple processors, where one processor maintains many fewer particles by communicating with neighboring processors. A numerical study as well as a theoretical analysis are provided to demonstrate the convergence of the parallel stochastic particle algorithm.
Part I, Symplectic ice, Part II, Global and local Kubota symbols [electronic resource]
Keywords: Mathematics

My Ph.D. thesis consists of two parts. In the first part I construct an ice-model (a six-vertex model). I show the partition function of this ice model is equal to the product of an irreducible character of the symplectic group and a deformation of the Weyl denominator. A similar result was originally proved by Hamel and King, but the Boltzmann weights (for the vertices at the caps) that I use are different then the ones that are used by Hamel and King. Also, my proof of this result uses Yang-Baxter equation (while the proof of Hamel and King does not). This gives us a 6-vertex models for characters of the symplectic group , but this result can also be interpreted as an example of an exactly solved model, that is, an ice model whose partition function can be computed explicitly (this is of interest to people who work in statistical mechanics). In the second part of my thesis I work with the global and local Kubota symbols. I introduce a local Kubota symbol, and show that it satisfies some properties that are satisfies by the global Kubota symbol; in particular, it satisfies the reciprocity law. Using the parallel between the properties of the global and local Kubota symbols, I give a new proof of Kubota's theorem (for the case when p does not divide n), and then generalize this theorem to the case when p divides n. In the last chapter of my thesis I work with the global Kubota symbol. I investigate the levels for the global Kubota symbols for particular fields, and I obtain new levels for these fields which improve the results of Kubota, and of Bass, Milnor and Serre.
Peer-to-peer video streaming with interactive region-of-interest [electronic resource]
Keywords: Electrical Engineering

Increasing spatial resolution offered by digital imaging sensors and growing capacities of storage devices are helping the rise of high-spatial-resolution digital video. Such videos offer the possibility of viewing an arbitrary region-of-interest (RoI) interactively. The user can pan/tilt/zoom while watching the video. This allows watching user-selected portions of high-resolution video even on displays of lower spatial resolution. In the case of remote streaming, it avoids transmitting the entire field-of-view in high resolution, thus reducing required data rate. The first main contribution of this thesis is spatial-random-access-enabled video compression. The goal is to encode the video content once such that arbitrary RoIs corresponding to different zoom factors can be extracted from the compressed bit-stream, thus avoiding a dedicated encoder for each user. We explore the trade-off between storage space and mean transmission bit-rate. We show how to choose the slice size for video coding for minimizing the mean transmission bit-rate. Recently, peer-to-peer (P2P) video streaming has shown good potential for enabling large-scale video multicast at much lower cost than currently applied techniques. The second main contribution of this thesis is the design of a P2P live multicast streaming system that allows each user to independently control pan/tilt/zoom while still exploiting the commonalities in their RoIs for delivering content in a P2P manner. We present a distributed P2P protocol, which is run at each client and allows each client to receive and relay relevant data in real time. The protocol is designed by keeping in mind that the overlaps among users' RoIs are highly transient. Our findings indicate that to support the same number of clients as traditional client-server unicast, our P2P approach requires much less server uplink bandwidth. We show how to allocate the server bandwidth for streaming regions that vary in popularity and rate-distortion operating points.
A penalized matrix decomposition, and its applications [electronic resource]
Keywords: Statistics

We present a penalized matrix decomposition, a new framework for computing a low-rank approximation for a matrix. This low-rank approximation is a generalization of the singular value decomposition. While the singular value decomposition usually yields singular vectors that have no elements that are exactly equal to zero, our new decomposition results in sparse singular vectors. This decomposition has a number of applications. When it is applied to a data matrix, it can yield interpretable results. One can apply it to a covariance matrix in order to obtain a new method for sparse principal components, and one can apply it to a crossproducts matrix in order to obtain a new method for sparse canonical correlation analysis. Moreover, when applied to a dissimilarity matrix, this leads to a method for sparse hierarchical clustering, which allows for the clustering of a set of observations using an adaptively chosen subset of the features. Finally, if this decomposition is applied to a between-class covariance matrix then it yields penalized linear discriminant analysis, an extension of Fisher's linear discriminant analysis to the high-dimensional setting.
Performance analysis and optimization of CSMA-based wireless mesh networks [electronic resource]
Keywords: Electrical Engineering

Wireless Mesh Networks consist of nodes interconnected by wireless links. User data packets are transported from sources to destinations over paths comprising of multiple wireless links. The functionality underlying nodes in a wireless mesh network consists of selection of paths between sources and destinations of traffic (Routing), coordination of access to the shared wireless medium (Media Access Control (MAC)), and transmission of data packets on the wireless channel (Physical Layer functionality). In most wireless mesh networks currently deployed, these functions follow the IEEE 802.11 standard, also known as "WiFi". In this standard, the MAC protocol is Carrier Sense Multiple Access (CSMA), whereby a node is blocked from transmitting when it senses the medium busy due to transmissions from other nodes in the network. In such networks, the performance is sensitive to both physical layer parameters and routing. In this thesis, we analyze the performance of CSMA-based wireless mesh networks, and determine how to select physical layer parameters and routes, so as to achieve the best performance possible. The first part of the thesis consists of the development of an analytical model for CSMA-based wireless mesh networks. The model accurately represents all aspects of the CSMA protocol in a multihop network (the effect of blocking, the effect of interference, and the acknowledgement traffic). The model is computationally more efficient than computer simulation models. The accuracy of results obtained by using the model has been verified by comparison to results obtained by using a high-fidelity simulation model. Given the propagation characteristics of wireless links in the network, and the traffic to be carried on these links, the model allows one to determine whether the traffic load is feasible or not. For a feasible load, it also provides link-related performance measures; namely, the average packet error rate on each link, and the fraction of time that the channel is sensed busy by the transmitter of each link. The second part of the thesis addresses specifically the performance optimization of CSMA-based wireless mesh networks. Key to achieving the best performance in a wireless mesh network is to maximize the number of transmissions that can take place concurrently in the network (i.e., the degree of spatial reuse of the wireless channel). This requires an optimum setting of physical layer parameters associated with links carrying traffic. The links carrying traffic are determined by the routing function, and the selection of these links is based on the links' physical layer parameters. Thus, achieving the best performance requires joint optimization of the physical layer parameters and routes. We consider networks in which the signal attenuation between nodes follows a power law function of distance. In that case, the best performance is achieved when routing uses links on which attenuation is in the lowest possible range, as this leads to the highest degree of spatial reuse.
The performance of justice in imperial Latin literature [electronic resource]
Keywords: Classics

This dissertation investigates the trial scene as a literary topos in early Imperial Latin Literature and how this topos reflects significant changes to the Roman legal system under the emperors. While past scholars have used historical and juristic sources to document what these changes to Roman law were, my dissertation analyzes literary evidence to understand how these changes were viewed by imperial authors. I argue that changes to the legal system are not only manifested in Latin literature but also that a study of the literature can help us better understand the cultural and societal impacts of changes to judicial procedure. Through the analysis and historical contextualization of trial scenes depicted in literature, I assert that imperial authors overwhelmingly represent the emperor in his role as judge (princeps iudex), and I assess accordingly the implications that this new source of legal authority has for a Roman understanding of truth and justice. More broadly, my research aims to bridge the gap between the study of Roman law and Latin literature by revealing that both disciplines evaluate how the Romans engaged in acts of truthseeking and of truthmaking.
Persistence and Recurrence of Internal Armed Conflict
Keywords: CISAC
Center for International Security and Cooperation
Stanford University
internal conflict
security
Thesis

This thesis analyzes factors that affect the duration and relapse of internal armed conflicts. I use a data set containing 173 conflicts that occurred worldwide between 1946 and 2008. I find that ethnically diverse, poor, and populous countries are prone to persistent and recurrent internal conflict. I find that decisive victories tend to be more stable than agreements, which in turn are more stable than conflicts that end due to low activity. My research indicates that peacekeepers are highly effective in reducing the chances that a conflict will relapse. Through a set of case studies focused on recurrence, I determine that countries with a large plurality ethnic group and several smaller groups are prone to recurrent conflict. In a second set of case studies, I argue that exogenous support for rebel organizations is crucial to sustaining many persistent conflicts. I stress that negotiators and policymakers must be acutely aware of the risks of recurrence when mediating internal conflicts. I recommend the deployment of peacekeepers to enforce agreements and the inclusion of ethnic minorities in government, especially in situations at high risk of relapse. Finally, I argue that isolating and neutralizing exogenous support for rebels is critical to ending persistent conflicts.
Persistent scatterer interferometry in natural terrain [electronic resource]
Keywords: Electrical Engineering

Time-series InSAR techniques are designed to estimate the temporal characteristics of surface deformation by combining information from multiple SAR images acquired over time. In many cases, these techniques also enable us to measure deformation signals in locations where conventional InSAR fails and also to reduce the error associated with deformation measurements. Among these techniques, Persistent Scatterer (PS) methods work by identifying the ground resolution elements that are dominated by a single scatterer. A persistent scatterer exhibits reduced baseline and temporal decorrelation due to its stable, point-like scattering mechanism. In PS analysis, a set of interferograms formed with a single master scene are processed at single look resolution in order to maximize the signal-to-clutter ratio (SCR) of the resolution elements containing a single dominant scatterer. In urban terrain, buildings and other man-made structures often act as PS due to their corner reflector-like scattering behavior and high radar reflectivity. Hence, traditional SAR amplitude-based PS-InSAR techniques have proved to be very e ffective in urban terrain. In natural terrain, the absence of bright manmade structures makes reliable estimation of deformation using PS-InSAR techniques a challenging task. The main obstacle is in the phase unwrapping stage, where the solutions are directly dependent on the PS network density. We have developed a two pronged approach to improve the applicability of PS-InSAR techniques to natural terrain - increasing PS network density and improving the reliability of phase unwrapping algorithms. We first present an information theoretic approach to PS pixel selection and demonstrate the ability of these new algorithms in identifying a denser network of PS in natural terrain. We then address the spatio-temporal (three dimensional) phase unwrapping problem applicable to sparse and non-uniformly sampled time-series InSAR data sets, and present two novel phase unwrapping algorithms. We demonstrate the efficacy of our new PS selection technique with experimental results from the San Francisco Bay Area, Lyngen region of Norway and the creeping section of the Central San Andreas Fault. We explain the salient features of our new "edgelist" phase unwrapping algorithm with results from the Central San Andreas Fault region north of Park field, CA. We provide detailed comparisons of the estimated line of sight velocity and deformation time-series with results from other time-series InSAR algorithms developed by research groups based in NORUT, Norway and IREA-CNR, Italy.
PET-CT small lesion quantitation and three-dimensional visualization [electronic resource]
Keywords: Bioengineering.

Positron Emission Tomography-Computerized Tomography (PET-CT) is a non-invasive molecular imaging technology that plays an important role in thoracic oncology. Currently, PET-CT images are used primarily for cancer staging by assessing the likelihood of malignancy and the likelihood for disease metastasis. More widespread adoption of this modality has been limited by its unreliability for characterizing small lesions affected by the partial volume effect. This dissertation focuses on several novel approaches for combined PET-CT image quantitation in the presence of partial volume effects and three-dimensional visualization to facilitate more accurate characterization of suspicious lung lesions.
Photo and dark current mechanisms in organic heterojunction solar cells [electronic resource]
Keywords: Materials Science and Engineering

Organic photovoltaic (OPV) cells can potentially become the renewable energy source of choice because of their advantages such as flexibility and low-cost. Over the past decade, extensive research attention has focused on increasing the power conversion efficiency of OPV cells with record efficiencies near 6%, still falling far short of the efficiency achieved in traditional inorganic solar cells. Further improvements in OPV cell performance will require a thorough understanding of the physical processes that govern photocurrent generation. It is usually assumed that non-geminate recombination is the most important loss mechanism that can be minimized by increasing the carrier mobilities. We have modeled the separation of the geminate charge-pair at a donor-acceptor interface of arbitrary geometry using kinetic Monte Carlo simulations. We find that the geminate carrier recombination process that takes place at the donor-acceptor immediately following exciton dissociation determines the shape of the photocurrent-voltage characteristics and contributes significantly to losses in organic donor-acceptor solar cells. The ratio of the electron mobility in the acceptor material over the hole mobility of the donor material (or vice versa), and not the absolute carrier mobility, determines the geminate separation probability and fill factor. These results are confirmed by intensity, voltage, intentional doping, and temperature dependent photocurrent measurements on planar and bulk heterojunctions. We performed capacitance-voltage measurements on simple bilayer organic solar cells as a function of temperature. These measurements provide information about the electrically active doping concentration and the ionization energy of these dopants. Band structures were calculated for the doping density and ionization energy typically found for various temperatures, and Monte Carlo simulations of the geminate pair separation process were performed, providing a complete model for photocurrent generation that matches experimental observations closely. The Shockley diode equation has been used extensively to explain the dark current in donor-acceptor organic heterojunctions, but without thorough justification. We show experimentally that these devices cannot be modeled accurately using Shockley's model. The fit to Shockley's diode equation is coincidental and holds for a single temperature only. A new model was proposed and shown to fit experimental data. The work provides precise guidelines for increasing the efficiency of organic heterojunction photovoltaic cells.