3,166 Works

Earthquake Source Characterization Through Seismic Observations and Numerical Modeling

Semechah Ka Yan Lui
In this thesis, I present a series of works on the characterization of source properties and physical mechanisms of various small to moderate earthquakes through both observational and numerical approaches. From the results, we find implications on a broader scheme of topics relating to larger earthquakes, shear zone structure, frictional properties of faults, and seismic hazard assessment. Part I consists of two studies using waveform modeling. In Chapter 2, we present an in-depth study of...

TCCON data from Caltech (US), Release GGG2014.R1

P. O. Wennberg, D. Wunch, C. M. Roehl, J.-F. Blavier, G. C. Toon & N. T. Allen
The Total Carbon Column Observing Network (TCCON) is a network of ground-based Fourier Transform Spectrometers that record direct solar absorption spectra of the atmosphere in the near-infrared. From these spectra, accurate and precise column-averaged abundances of atmospheric constituents including CO2, CH4, N2O, HF, CO, H2O, and HDO, are retrieved. This data set contains observations from the TCCON station at the California Institute of Technology, Pasadena, U.S.A..

Convex Model Predictive Control for Vehicular Systems

Tiffany Amy Huang
In this work, the author presents a method called Convex Model Predictive Control (CMPC) to control systems whose states are elements of the rotation matrices SO(n) for n = 2, 3. This is done without charts or any local linearization, and instead is performed by operating over the orbitope of rotation matrices. This results in a novel model predictive control (MPC) scheme without the drawbacks associated with conventional linearization techniques such as slow computation time...

Virology By The Numbers: A Quantitative Exploration of Viral Energetics, Genomics, and Ecology

Gita Mahmoudabadi
Over the past couple of decades, technological advancements in sequencing and imaging have unequivocally proven that the world of viruses is far bigger and more consequential than previously imagined. There are 1031 viruses estimated to inhabit our planet, outnumbering even bacteria. Despite their astronomical numbers and staggering sequence diversity, environmental viruses are poorly characterized. In this thesis we will demonstrate our three-pronged exploration of viruses through the lenses of energetics (Chapters 2 and 3), genomics...

Dynamics of Granular Crystals with Elastic-Plastic Contacts

Hayden Andrew Burgoyne
We study the behavior of granular crystals subjected to impact loading that creates plastic deformation at the contacts between constituent particles. Granular crystals are highly periodic arrangements of spherical particles, arranged into densely packed structures resembling crystals. This special class of granular materials has been shown to have unique dynamics with suggested applications in impact protection. However, previous work has focused on very low amplitude impacts where every contact point can be described using the...

On the Evolutionary Pathways of Stars and Extrasolar Planets

Trevor Justin David
In this thesis, I present several studies aimed at determining the evolutionary states of stars and the planets that orbit them. Multiple approaches are undertaken to determine the physical parameters of stars over a wide range of masses, and in the process I evaluate current theoretical models which are commonly used to indirectly determine the properties of stars and planets. Chapter II concerns the ages of nearby stars more massive than the Sun. These stars,...

Proteomic Analysis of the Cdc48/Ubx Network Identifies a Role for Ubx2 in the Regulation of Lipid Biosynthesis

Natalie J. Kolawa
Cdc48/p97 is an essential, highly abundant hexameric member of the AAA (ATPase associated with various cellular activities) family. It has been linked to a variety of processes throughout the cell but it is best known for its role in the ubiquitin proteasome pathway. In this system it is believed that Cdc48 behaves as a segregase, transducing the chemical energy of ATP hydrolysis into mechanical force to separate ubiquitin-conjugated proteins from their tightly-bound partners. Current models...

Numerical Simulations of Black-Hole Spacetimes

Tony Chu
This thesis covers various aspects of the numerical simulation of black-hole spacetimes according to Einstein's general theory of relativity, using the Spectral Einstein Code developed by the Caltech-Cornell-CITA collaboration. The first topic is improvement of binary-black-hole initial data. One such issue is the construction of binary-black-hole initial data with nearly extremal spins that remain nearly constant during the initial relaxation in an evolution. Another concern is the inclusion of physically realistic tidal deformations of the...

Physical, Metabolic, and Energetic Investigations of Methane-Metabolizing Microbial Communities

Jeffrey James Marlow
Understanding the roles of microorganisms in environmental settings by linking phylogenetic identity to metabolic function is a key challenge in delineating their broad-scale impact and functional diversity throughout the biosphere. This work addresses and extends such questions in the context of marine methane seeps, which represent globally relevant conduits for an important greenhouse gas. Through the application and development of a range of culture-independent tools, novel habitats for methanotrophic microbial communities were identified, established settings...

Understanding Co-translational Protein Targeting and Lithium Dendrite Formation through Free Energy Simulations and Coarse-Grained Models

Connie Yuan-Ying Wang
We describe the application of alchemical free energy methods and coarse-grained models to study two key problems: (i) co-translational protein targeting and insertion to direct membrane proteins to the endoplasmic reticulum for proper localization and folding, (ii) lithium dendrite formation during recharging of lithium metal batteries. We show that conformational changes in the signal recognition particle, a central component of the protein targeting machinery, confer additional specificity during the the recognition of signal sequences. We...

Development of Cu- and Ni-Catalyzed C–C and C–N Bond Forming Reactions

Shoshana Bachman
Chapters 1 and 2 describe the development of photoinduced, Cu-catalyzed coupling reactions of unactivated secondary alkyl halides with amide and cyanide nucleophiles. These reactions may be conducted at room temperature under operationally simple conditions. Mechanistic studies are consistent with the intermediacy of alkyl radicals in these processes. Chapter 3 describes progress toward the development of the first enantioselective Ni-catalyzed cross coupling of racemic alkyl halides and heteroatom nucleophiles. Borylation of secondary benzylic chlorides with B2(pin)2...

Distributed Load Control in Multiphase Radial Networks

Lingwen Gan
The current power grid is on the cusp of modernization due to the emergence of distributed generation and controllable loads, as well as renewable energy. On one hand, distributed and renewable generation is volatile and difficult to dispatch. On the other hand, controllable loads provide significant potential for compensating for the uncertainties. In a future grid where there are thousands or millions of controllable loads and a large portion of the generation comes from volatile...

Tools and Algorithms for Sampling in Extreme Terrains

Melissa Tanner, Joel Burdick & Issa Nesnas
Extreme-terrain robots such as JPL’s Axel rover are enabling access to new and exciting science opportunities. The goal of this mini-program was to develop a compact sampling instrument for Axel. Over the summer of 2012, a small group of students designed, built, and tested prototype sampling devices. Nikola Georgiev created a versatile four-degree-of-freedom scoop, which can acquire up to 4 different samples in clean self-sealing containers. Hima Hassenruck-Gudipati studied percussive scooping, and prototyped a percussive...

Redox Kinetics of Nonstoichiometric Oxides

Ho-Il Ji
Cerium oxide (CeO2-δ) and its derivatives are the most attractive materials under consideration for solar-driven thermochemical production of chemical fuels. Understanding the rate-limiting factors in fuel production is essential for maximizing the efficacy of the thermochemical process. The rate of response of the porous ceria structured with architectural features typical of those employed in solar reactors was measured via electrical conductance relaxation methods. A transition from behavior controlled by material surface reaction kinetics to that...

Simulation of Richtmyer-Meshkov Flows for Elastic-Plastic Solids in Planar and Converging Geometries Using an Eulerian Framework

Alejandro Lopez Ortega
This thesis presents a numerical and analytical study of two problems of interest involving shock waves propagating through elastic-plastic media: the motion of converging (imploding) shocks and the Richtmyer-Meshkov (RM) instability. Since the stress conditions encountered in these cases normally produce large deformations in the materials, an Eulerian description, in which the spatial coordinates are fixed, is employed. This formulation enables a direct comparison of similarities and differences between the present study of phenomena driven...

Imprints of Massive Scalars on Primordial Non-Gaussianities

Alexander Karas Ridgway
In this thesis, we modify the standard single-field inflation scenario by adding additional massive scalars to the inflationary field content. Due to the breaking of time translational invariance by the inflaton background, the inflaton can interact with these extra scalars through a kinetic mixing term. If these scalars have self- interactions, then their kinetic mixings with the inflaton induce potentially large primordial non-gaussianities in the scalar curvature fluctuations, which could be observed in the cosmic...

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