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Full-Text Articles in Physical Sciences and Mathematics

Aztec Survey Of The Central Molecular Zone: Modeling Dust Seds With Hierarchical Bayesian Analysis, Yuping Tang Jul 2019

Aztec Survey Of The Central Molecular Zone: Modeling Dust Seds With Hierarchical Bayesian Analysis, Yuping Tang

Doctoral Dissertations

In this dissertation, we present a study based on the AzTEC/Large Millimeter Telescope (LMT) survey of dust continuum at 1.1mm on the central 200 parsecs (The Central Molecular Zone (CMZ)) of our Galaxy. Owing to its unusually high gas density and turbulence, strong magnetic field, and high cosmic ray flux, the CMZ represents an initial condition for star-formation typical of starburst galaxies in the distant universe. In order to understand dust properties in such an extreme environment. We perform a joint SED analysis of existing dust continuum surveys on the CMZ, from a wavelength of 160 μm to 1.1 mm. …

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Allocative Poisson Factorization For Computational Social Science, Aaron Schein Jul 2019

Allocative Poisson Factorization For Computational Social Science, Aaron Schein

Doctoral Dissertations

Social science data often comes in the form of high-dimensional discrete data such as categorical survey responses, social interaction records, or text. These data sets exhibit high degrees of sparsity, missingness, overdispersion, and burstiness, all of which present challenges to traditional statistical modeling techniques. The framework of Poisson factorization (PF) has emerged in recent years as a natural way to model high-dimensional discrete data sets. This framework assumes that each observed count in a data set is a Poisson random variable $y ~ Pois(\mu)$ whose rate parameter $\mu$ is a function of shared model parameters. This thesis examines a specific …

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A Study On Homogeneous Sheared Stably Stratified Turbulence, Gavin Portwood Jul 2019

A Study On Homogeneous Sheared Stably Stratified Turbulence, Gavin Portwood

Doctoral Dissertations

Homogeneous sheared and stably stratified turbulence is considered as a fundamental flow relevant to the study of geophysical turbulence and, generally, anisotropic turbulence. Numerical experiments are performed via high resolution direct numerical simulation (DNS) in a geophysically-relevant parameter space previously inaccessible to simulation. Turbulent dynamics relevant to the modeling of geophysical hydrodynamics are investigated as a function of mean flow and fluid parameters. An active tuning scheme is implemented to induce temporally stationary turbulent kinetic energy in order to evaluate turbulence that is statistically independent of initial conditions and spatio-temporally homogeneous. Subject to this constraint, the parametric dependence of the …

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Double-Network Materials Via Frontal Polymerization & Supercritical Co2 Processing, Matthew Joseph Lampe Jul 2019

Double-Network Materials Via Frontal Polymerization & Supercritical Co2 Processing, Matthew Joseph Lampe

Doctoral Dissertations

This dissertation presents work focused on producing materials in non-equilibrium states by taking advantage of novel processing techniques. First, epoxy-based resins which can undergo radically promoted, cationic, thermal, frontal polymerization are investigated for their potential use as adhesives. These resins are found to be capable of sustaining propagating polymerization fronts between several different substrate materials, resulting in high levels of adhesion in some cases. In addition, a similar frontal resin was developed that can undergo sequential gelation and frontal polymerization. The gels are formed by radically crosslinking acrylate monomers within the epoxy resin. These gels can then be manipulated, and …

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Probabilistic Models For Identifying And Explaining Controversy, Myungha Jang Jul 2019

Probabilistic Models For Identifying And Explaining Controversy, Myungha Jang

Doctoral Dissertations

Navigating controversial topics on the Web encourages social awareness, supports civil discourse, and promotes critical literacy. While search of controversial topics particularly requires users to use their critical literacy skills on the content, educating people to be more critical readers is known to be a complex and long-term process. Therefore, we are in need of search engines that are equipped with techniques to help users to understand controversial topics by identifying them and explaining why they are controversial. A few approaches for identifying controversy have worked reasonably well in practice, but they are narrow in scope and exhibit limited performance. …

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Reactive And Stimuli-Responsive Sulfonium-Based Polymer Zwitterions, Cristiam Santa Chalarca Jul 2019

Reactive And Stimuli-Responsive Sulfonium-Based Polymer Zwitterions, Cristiam Santa Chalarca

Doctoral Dissertations

This dissertation describes the synthesis and characterization of novel monomers and (co)polymer zwitterions that incorporate trialkylsulfonium cations. The novel materials presented herein constitute a unique type of polymer zwitterions that exhibit salt- and temperature-dependent water solubility as well as inherent reactivity. The behavior of these polymers in aqueous solutions, as nanostructures, and at liquid-liquid interfaces was studied; in all cases, the inherent reactivity of the polymers was harnessed towards the fabrication of novel polymers and soft materials. Following an introductory chapter, Chapter 2 describes the synthesis of sulfonium sulfonate monomers and polymer zwitterions. Both styrenic and methacrylic monomers were synthesized …

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Abstractions In Reasoning For Long-Term Autonomy, Kyle Hollins Wray Jul 2019

Abstractions In Reasoning For Long-Term Autonomy, Kyle Hollins Wray

Doctoral Dissertations

The path to building adaptive, robust, intelligent agents has led researchers to develop a suite of powerful models and algorithms for agents with a single objective. However, in recent years, attempts to use this monolithic approach to solve an ever-expanding set of complex real-world problems, which increasingly include long-term autonomous deployments, have illuminated challenges in its ability to scale. Consequently, a fragmented collection of hierarchical and multi-objective models were developed. This trend continues into the algorithms as well, as each approximates an optimal solution in a different manner for scalability. These models and algorithms represent an attempt to solve pieces …

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Asymptotic And Numerical Analysis Of Coherent Structures In Nonlinear Schrodinger-Type Equations, Cory Ward Jul 2019

Asymptotic And Numerical Analysis Of Coherent Structures In Nonlinear Schrodinger-Type Equations, Cory Ward

Doctoral Dissertations

This dissertation concerns itself with coherent structures found in nonlinear Schrödinger-type equations and can be roughly split into three parts. In the first part we study a deformation of the defocusing nonlinear Schrödinger (NLS) equation, the defocusing Camassa-Holm NLS (CH-NLS) equation in both one and two space dimensions. We use asymptotic multiscale expansion methods to reduce this model to a Boussinesq-like equation, which is then subsequently used to obtain approximate solitary wave solutions for both the 1D and 2D CH-NLS equations. We then use direct numerical simulations to investigate the validity of these approximate solutions, their evolution, and their head-on …

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Synthesis Of Magnetic Ion Doped Ii-Vi Benzenechalcogenolate Molecular Clusters, Fumitoshi Kato Jul 2019

Synthesis Of Magnetic Ion Doped Ii-Vi Benzenechalcogenolate Molecular Clusters, Fumitoshi Kato

Doctoral Dissertations

Diluted magnetic semiconductor quantum dots (DMS-QDs) is a class of material prepared by introducing a small percentage of magnetic impurities to impart new magneto-optical properties to the host nanocrystal (NC). Such materials are regarded as promising candidates for their potential application in spintronic devices. The overall functionality of the DMS‑QD is highly dependent on the dopant position within the host structure. A thorough understanding of the doping mechanism is, therefore, critical to gain better control over the dopant speciation in nanocrystal lattice and material properties. In this work, we utilized II‑VI molecular clusters that are analogous to bulk semiconductors as …

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Flow-Induced Oscillations In Floating Offshore Wind Turbines, Daniel Carlson Jul 2019

Flow-Induced Oscillations In Floating Offshore Wind Turbines, Daniel Carlson

Doctoral Dissertations

The goal of this thesis is to experimentally study the structural dynamics, wake interaction, and fluid forces on the multiple-degree of freedom systems typical of floating wind turbines. Vortex--surface alignment about flexibly-mounted prisms is studied to investigate the response of barges and semi-submersible hulls, and new results pertaining to the galloping response kink for a prism with dual inline--crossflow resonance is presented. Flow--induced oscillations of a spar model free to rotate in 3D space is replicated and observed as 2D figure--eight orbits about the center of the spar. Methods to suppress the flow from exciting the spar are proposed. The …

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Data-Driven Approach To Image Classification, Venkatesh Narasimhamurthy Jul 2019

Data-Driven Approach To Image Classification, Venkatesh Narasimhamurthy

Doctoral Dissertations

Image classification has been a core topic in the computer vision community. Its recent success with convolutional neural network (CNN) algorithm has led to various real world applications such as large scale management of photos/videos on cloud/social-media, image based search for online retailers, self-driving cars, building robots and healthcare. Image classification can be broadly categorized into binary, multi-class and multi-label classification problems. Binary classification involves assigning one of the two class labels to an instance. In multi-class classification problem, an instance should be categorized into one of more than two classes. Multi-label classification is a generalized version of the multi-class …

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Modulating Dopant-Defect Interactions In Transition Metal Doped Colloidal Strontium Titanate Nanocrystals, William Harrigan Jul 2019

Modulating Dopant-Defect Interactions In Transition Metal Doped Colloidal Strontium Titanate Nanocrystals, William Harrigan

Doctoral Dissertations

Perovskites such as strontium titanate, a wide band gap semiconductor have been widely studied due to the multitude of potential applications in photocatalysis, multiferroics, sensing, and microelectronics. Various novel optical, electrical and magnetic properties can be imparted through the introduction of different transition metal dopant ions. The introduction of these impurities has been shown to impart functionality for various applications. The use of Cr3+has been shown to introduce defect levels into the band structure of SrTiO3and increase visible light utilization for photocatalysis. Transition metal doped highly crystalline colloidal SrTiO3nanocrystals (NC) were synthesized using two …

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Northeastern Species In Hybrid Cross Laminated Timber, Hamid Kaboli Jul 2019

Northeastern Species In Hybrid Cross Laminated Timber, Hamid Kaboli

Doctoral Dissertations

Known in the building industry throughout the world, Cross Laminated Timber (CLT) is a massive timber building material with outstanding structural, fire, and seismic properties. CLT is a cost-competitive, sustainable construction material is a good candidate as a substitute material for concrete, masonry, and steel, in mid-rise and high-rise buildings. CLT is perpendicular layers of dimensional lumbers usually laminated together and forming a massive structural panel. This dissertation explores the viability of utilizing Massachusetts grown Eastern Hemlock and Eastern White Pine in CLT panels as pure or in conjunction with other high-value wood products. 59% of Massachusetts’ lands are covered …

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Massive Graph Analysis In The Data Stream Model, Sofya Vorotnikova Jul 2019

Massive Graph Analysis In The Data Stream Model, Sofya Vorotnikova

Doctoral Dissertations

Graphs have become an abstraction of choice in modeling highly-structured data. The need to compute graph-theoretic properties of datasets arises in many applications that involve entities and pairwise relations between them. However, in practice the datasets in question can be too large to be stored in main memory, distributed across many machines, or changing over time. Moreover, in an increasing number of applications the algorithm has to make real time decisions as the data arrives, which puts further limitations on the time and space that can realistically be used. These characteristics render classical algorithmic approaches obsolete and necessitate the development …

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Sorption Temperature And And The Stability Of Iron-Bound Soil Organic Matter, Michael L. Nguyen Jul 2019

Sorption Temperature And And The Stability Of Iron-Bound Soil Organic Matter, Michael L. Nguyen

Doctoral Dissertations

The preservation of soil organic matter (SOM) is an important control on the global cycling of carbon. Long-term preservation of SOM has important implications on soil fertility and climate regulation. Minerals, such as iron oxides, can react with SOM and serve as a preservation mechanism for SOM. Globally, iron oxide-SOM interactions form a “rusty carbon sink” which protects up to 22% of organic carbon in marine sediments. Climate changes, such as warming, may alter the size or efficacy of the “rusty carbon sink.” The effects of temperature, SOM composition, and mineral particle size on the formation and stability of iron …

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Simulating Hydrogen Bonded Clusters And Zeolite Clusters For Renewable Energy Applications, Qinfang Sun Jul 2019

Simulating Hydrogen Bonded Clusters And Zeolite Clusters For Renewable Energy Applications, Qinfang Sun

Doctoral Dissertations

Our research attention is focused on the development of new fuel cell membrane materials and new zeolites which improve biomass conversion rate to meet the increasing demand of renewable and sustainable energy. We have simulated the dynamics of amphiprotic groups (pyrazole, imidazole, 1,2,3-triazole, 1,2,4-triazole, and tetrazole, acetic acid, formic acid, sulfuric acid, and phosphoric acid) as neat liquids and tethered via linkers to aliphatic backbones, to determine how tethering and varying functional groups affect hydrogen bond networks and reorientation dynamics, both factors thought to influence proton conduction. We used the DL_Poly_2 molecular dynamics code with the GAFF force field to …

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Poetry: Identification, Entity Recognition, And Retrieval, John J. Foley Iv Jul 2019

Poetry: Identification, Entity Recognition, And Retrieval, John J. Foley Iv

Doctoral Dissertations

Modern advances in natural language processing (NLP) and information retrieval (IR) provide for the ability to automatically analyze, categorize, process and search textual resources. However, generalizing these approaches remains an open problem: models that appear to understand certain types of data must be re-trained on other domains. Often, models make assumptions about the length, structure, discourse model and vocabulary used by a particular corpus. Trained models can often become biased toward an original dataset, learning that – for example – all capitalized words are names of people or that short documents are more relevant than longer documents. As a result, …

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Multiscale Simulations Of Intrinsically Disordered Proteins, Xiaorong Liu Jul 2019

Multiscale Simulations Of Intrinsically Disordered Proteins, Xiaorong Liu

Doctoral Dissertations

Intrinsically disordered proteins (IDPs) lack stable secondary and/or tertiary structures under physiological conditions. The have now been recognized to play important roles in numerous biological processes, particularly cellular signaling and regulation. Mutation of IDPs are frequently associated with human diseases, such as cancers and neuron degenerative diseases. Therefore, it is important to understand the structure, dynamics, and interactions of IDPs, so as to establish the mechanistic basis of how intrinsic disorder mediates versatile functions and how such mechanisms may fail in human diseases. However, the heterogeneous structural ensembles of IDPs are not amenable to high resolution characterization solely through experimental …

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Design, Synthesis And Study Of Functional Amphiphilic Polymers And Their Applications, Huan He Jul 2019

Design, Synthesis And Study Of Functional Amphiphilic Polymers And Their Applications, Huan He

Doctoral Dissertations

Amphiphilic homopolymers with high densities of functional groups are synthetically challenging. Thiol-yne nucleophilic click reactions have been investigated to introduce multiple functional groups in polymers with high density. An electron deficient alkyne group bearing methacrylate monomer was polymerized using reversible addition−fragmentation chain-transfer (RAFT) polymerization. Subsequently, the electron deficient alkyne group on polymer side chain was readily reacted with a thiol reagent using triethylamine (TEA) as the organocatalyst. This reaction was found to be very efficient under mild conditions. The resultant homopolymer bearing thiol vinyl ether functional groups could perform a second thiol addition with a stronger base, such as triazabicyclodecene(TBD), …

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Methods For Making Policy-Relevant Forecasts Of Infectious Disease Incidence, Stephen A. Lauer Jul 2019

Methods For Making Policy-Relevant Forecasts Of Infectious Disease Incidence, Stephen A. Lauer

Doctoral Dissertations

Infectious diseases place an enormous burden on the people of the developing world and their governments. When, where, and how to allocate resources in order to slow the spread of a virus or deal with the aftermath of an outbreak is often the responsibility of local public health officials. In this thesis, we develop statistical methods for forecasting future incidence of infectious diseases and estimating the effects of interventions designed to reduce future incidence, bearing in mind the needs and concerns of those public health officials. While most infectious disease forecasting models focus on short-term horizons (i.e. weeks or …

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Modification Of 2d Materials Utilizing Functional Polymer Interfacial Layers, Ryan Selhorst Jul 2019

Modification Of 2d Materials Utilizing Functional Polymer Interfacial Layers, Ryan Selhorst

Doctoral Dissertations

This dissertation describes the modification of 2D transition metal dichalcogenides (TMDCs). These materials exhibit unique electronic properties, ranging from metallic to insulating, and can transport either electrons (n-type) or holes (p-type). Polymers containing electronically-active moieties offer a path to control the electronic properties of a 2D material without altering the inherent structure of the semiconductor. This dissertation focuses on the synthesis of polymers bearing chalcogen-rich or zwitterionic moieties to alter the electronic and solution properties of 2D materials. Chapter 2 describes polymers containing sulfur-rich tetrathiafulvalene (TTF) and their effects as electroactive coatings on the TMDC molybdenum disulfide (MoS2). …

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From Optimization To Equilibration: Understanding An Emerging Paradigm In Artificial Intelligence And Machine Learning, Ian Gemp Jul 2019

From Optimization To Equilibration: Understanding An Emerging Paradigm In Artificial Intelligence And Machine Learning, Ian Gemp

Doctoral Dissertations

Many existing machine learning (ML) algorithms cannot be viewed as gradient descent on some single objective. The solution trajectories taken by these algorithms naturally exhibit rotation, sometimes forming cycles, a behavior that is not expected with (full-batch) gradient descent. However, these algorithms can be viewed more generally as solving for the equilibrium of a game with possibly multiple competing objectives. Moreover, some recent ML models, specifically generative adversarial networks (GANs) and its variants, are now explicitly formulated as equilibrium problems. Equilibrium problems present challenges beyond those encountered in optimization such as limit-cycles and chaotic attractors and are able to abstract …

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Hierarchical Belief Spaces For Autonomous Mobile Manipulation, Michael W. Lanighan Jul 2019

Hierarchical Belief Spaces For Autonomous Mobile Manipulation, Michael W. Lanighan

Doctoral Dissertations

Autonomy in robot systems is a valuable attribute that remains an elusive goal. Noisy sensors, stochastic actions, and variation in unstructured environments all lead to unavoidable errors that can be inconsequential or catastrophic depending on the circumstances. Developing techniques capable of mitigating uncertainty at runtime has, therefore, been a significant and challenging focus of the robotics community. The primary contribution of this dissertation is the introduction of a new hierarchical belief space planning architecture to manage uncertainty and solve tasks using a uniform framework. Such an approach provides a means of creating autonomous systems that focus on salient subsets of …

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Eastern Whip-Poor-Will Habitat Associations In Fort Drum, Ny, Kimberly Spiller Jul 2019

Eastern Whip-Poor-Will Habitat Associations In Fort Drum, Ny, Kimberly Spiller

Masters Theses

The eastern whip-poor-will (Antrostomus vociferus: hereafter whip-poor-will) has been declining from historical population levels throughout its range in the northeast. Although whip-poor-wills have been reported to use a variety of habitats, most recent studies have associated whip-poor-wills with open habitat, such as early-successional habitats or forest edges. Population declines of other early-successional bird species have been attributed to the loss of early-successional disturbance-dependent habitats in the northeast, and it has been suggested that habitat loss is a significant factor in whip-poor-will population declines, as well. However, there remain substantial gaps in our understanding of whip-poor-will habitat associations, and …

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The Climatic And Hydrostratigraphic Controls On Brine-To-Freshwater Interface Dynamics In Hyperarid Climates: A 2-D Parametric Groundwater Modeling Study, Sarah Mcknight Jul 2019

The Climatic And Hydrostratigraphic Controls On Brine-To-Freshwater Interface Dynamics In Hyperarid Climates: A 2-D Parametric Groundwater Modeling Study, Sarah Mcknight

Masters Theses

Density dependent flow occurs in areas where high-salinity groundwater interacts with low-salinity groundwater to create a brine-to-freshwater interface that defies common assumptions about groundwater movement. Yet the geologic and hydrologic factors that impact interface dynamics and migration remain poorly defined. With less than 20 mm•yr-1 of precipitation and with an extremely dense (i.e. 1.2 g•cm-3) naturally occurring brine, Chile’s Salar de Atacama (SdA) provides an excellent analog for exploring interface dynamics in other arid regions. Site-specific 2-D models of the interface in the southeastern region of SdA, with interpretations of the hydrostratigraphic framework, provide an analysis for …

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Efficient Probabilistic Reasoning Using Partial State-Space Exploration, Luis Pineda Mar 2019

Efficient Probabilistic Reasoning Using Partial State-Space Exploration, Luis Pineda

Doctoral Dissertations

Planning, namely the ability of an autonomous agent to make decisions leading towards a certain goal, is one of the fundamental components of intelligent behavior. In the face of uncertainty, this problem is typically modeled as a Markov Decision Process (MDP). The MDP framework is highly expressive, and has been used in a variety of applications, such as mobile robots, flow assignment in heterogeneous networks, optimizing software in mobile phones, and aircraft collision avoidance. However, its wide adoption in real-world scenarios is still impaired by the complexity of solving large MDPs. Developing effective ways to tackle this complexity barrier is …

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Bio-Inspired Polymers That Bind And Deliver Protein Cargo, Nicholas D. Posey Mar 2019

Bio-Inspired Polymers That Bind And Deliver Protein Cargo, Nicholas D. Posey

Doctoral Dissertations

Delivering functional proteins and antibodies into cells can allow researchers to probe the intracellular environment, discover new cellular pathways, and pioneer new therapeutics. However, the entry of exogenous, charged molecules, like proteins, into the cell is usually restricted by the membrane, thereby hindering intracellular delivery. Membrane permeable molecules such as cell penetrating peptides (CPPs) and protein transduction domains (PTDs) can be used to bypass the cell membrane and deliver protein into the cell, but these peptides involve iterative and laborious syntheses and are limited in terms of their chemical diversity. This dissertation work overall focuses on the design and synthesis …

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Quantitative Probing Of Vacancies And Ions Dynamics In Electroactive Oxide Materials, Jiaxin Zhu Mar 2019

Quantitative Probing Of Vacancies And Ions Dynamics In Electroactive Oxide Materials, Jiaxin Zhu

Doctoral Dissertations

Oxygen vacancy and ion dynamics in functional oxides are critical factors influencing electrical conductivity and electrochemical activity of oxides assemblies. The recent advancements in deposition and fabrication of oxide heterostructured films with atomic-level precision has led to discovery of intriguing physical properties and new artificial materials. While still under debate, researchers most often attribute these observed behaviors to unique oxygen vacancy distributions in the substrate near heterointerfaces. In electroactive oxides devices such as solid oxide cells (SOCs), oxygen vacancy and ion transport at the triple-phase boundary determines the performance of the device. This complex process motivates numerous remaining questions regarding …

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Enhanced Mass Spectrometric Analysis Of Peptides And Proteins Using Polymeric Reverse Micelles, Mahalia Adelina Corazon Paningbatan Serrano Mar 2019

Enhanced Mass Spectrometric Analysis Of Peptides And Proteins Using Polymeric Reverse Micelles, Mahalia Adelina Corazon Paningbatan Serrano

Doctoral Dissertations

Mass spectrometry (MS) has become a key and indispensable tool in the identification, characterization, and quantitative analysis of proteins owing to its universality, sensitivity, specificity, and its capability for multiplexed detection. Because biological samples containing these protein analytes are almost always complex systems, various techniques are employed in conjunction with MS to fully harness its analytical potential and enhance its detection capabilities. This dissertation explores the use of amphiphilic polymeric reverse micelles in enriching proteins and peptides from complex biological mixtures and in enhancing their mass spectrometric analysis. Fundamental studies that elucidate the molecular basis for the observed MS signal …

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Probing Quantized Excitations And Many-Body Correlations In Transition Metal Dichalcogenides With Optical Spectroscopy, Shao-Yu Chen Mar 2019

Probing Quantized Excitations And Many-Body Correlations In Transition Metal Dichalcogenides With Optical Spectroscopy, Shao-Yu Chen

Doctoral Dissertations

Layered transition metal dichalcogenides (TMDCs) have attracted great interests in recent years due to their physical properties manifested in different polytypes: Hexagonal(H)-TMDC,which is semiconducting, exhibits strong Coulomb interaction and intriguing valleytronic properties; distorted octahedral(T’)-TMDC,which is semi-metallic, is predicted to exhibit rich nontrivial topological physics. In this dissertation,we employ the polarization-resolved micron-Raman/PL spectroscopy to investigate the optical properties of the atomic layer of several polytypes of TMDC. In the first part for polarization-resolved Raman spectroscopy, we study the lattice vibration of both H and T’-TMDC, providing a thorough understanding of the polymorphism of TMDCs. We demonstrate that Raman spectroscopy is a …

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