452 Works

Supporting data for: Estimate of OH trends over one decade in North American cities

Qindan Zhu, Josh Laughner & Ron Cohen
The hydroxyl radical (OH) is the most important oxidant on global and local scales in the troposphere. Urban OH controls the removal rate of primary pollutants and triggers the production of ozone. Interannual trends of OH in urban areas are not well documented or understood due to the short lifetime and high spatial heterogeneity of OH. We utilize machine learning with observational inputs emphasizing satellite remote sensing observations to predict surface OH in 49 North...

On the Variational Principles of Linear and Nonlinear Resolvent Analysis

Benedikt Barthel
Despite decades of research, the accurate and efficient modeling of turbulent flows remains a challenge. However, one promising avenue of research has been the resolvent analysis framework pioneered by McKeon and Sharma (2010) which interprets the nonlinearity of the Navier-Stokes equations (NSE) as an intrinsic forcing to the linear dynamics. This thesis contributes to the advancement of both the linear and nonlinear aspects of resolvent analysis (RA) based modeling of wall bounded turbulent flows. On...

ACE Solar Wind Electron Proton Alpha Monitor (SWEPAM) 64-Second Level 2 Data

David McComas, Ruth Skoug, Dot Delapp, Heather Elliott & Andrew Davis
Solar Wind Ion parameters from ACE/SWEPAM. Level 2 data, 64-second averages. Parameters include proton density, temperature (radial component) and flow speed, flow velocity vector in GSE, GSM and RTN coordinates, and alpha to proton density ratio. ACE position vectors in GSE and GSM are included. The data are accessible via ftp in HDF and CDF from the ACE Science Center and CDAWeb, respectively, and in ASCII format from the value-added interfaces at those sites. Hourly...

ACE Solar Wind Electron Proton Alpha Monitor (SWEPAM) Suprathermal Electron Pitch Angle 128-Second Level 3 Data

David McComas, Ruth Skoug, Dot Delapp, Heather Elliott & Andrew Davis
Suprathermal Electron Pitch Angle data from ACE/SWEPAM. Level 3 data, 128-second averages. These pitch angle distributions are calculated automatically by a computer code, and have not been validated by a person. It is therefore likely that they include some artifacts and erroneous values. These data files contain suprathermal electron pitch angle distribution functions (s^3 cm^-6) at 272 eV from the ACE/SWEPAM-E instrument. The energy channel is ~12% wide, centered at 272 eV. Pitch angle bins...

Random Quantum Circuits and Their Simulation Complexity: An Analysis With Statistical Mechanics

Alexander M. Dalzell
Random circuit simulation, the task of replicating the output of a randomly chosen noiseless quantum computation, has been proposed as a path toward achieving quantum advantage: it is believed to be easy for quantum devices, but hard for classical ones. This thesis scrutinizes both sides of this belief. On the one hand, we investigate whether the task is classically hard—we find that, in certain non-trivial cases, it can actually be easy, complicating a potential general...

Single Neuron Correlates of Learning, Value, and Decision in the Human Brain

Tomas Gallo Aquino
In this thesis, I present several new results on how the human brain performs value-based learning and decision-making, leveraging rare single neuron recordings from epilepsy patients in vmPFC, preSMA, dACC, amygdala, and hippocampus, as well as reinforcement learning models of behavior. With a probabilistic gambling task we determined that human preSMA neurons integrate computational components of stimulus value such as expected values, uncertainty, and novelty, to encode an utility value and, subsequently, decisions themselves. Additionally,...

TCCON data from Ny-Ålesund, Svalbard (NO), Release GGG2020.R0

M. Buschmann, C. Petri, M. Palm, T. Warneke & J. Notholt
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 is the GGG2020 data release of observations from the TCCON station at Ny-Ålesund, Svalbard, Norway

TCCON data from Bremen (DE), Release GGG2020.R0

J. Notholt, C. Petri, T. Warneke & M. Buschmann
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 is the GGG2020 data release of observations from the TCCON station at Bremen, Germany

New Methods for the Study of Intramolecular and Solvent Dynamics

Aseem Mehta
Some of the fastest processes of relevance to chemical physicists occur on pico to femtosecond timescales. In the following chapters two of such fast processes axe investigated with novel theoretical methods to obtain insight into experimental observations at the molecular level. One of the major topics of interest in chemical physics has been about energy localization in polyatomic molecules. The "golden rule" formula states that the rate for the intramolecular relaxation of energy (IVR) that...

Bioorthogonal Noncanonical Amino Acid Tagging for Understanding Bacterial Persistence

Xinyan Liu
Phenotypic heterogeneity in populations of isogenic bacterial cells includes variations in metabolic rates and responses to antibiotic treatment. In particular, sub-populations of “persister” cells exhibit increased antibiotic tolerance. Understanding the mechanisms that underlie bacterial persistence would constitute an important step toward preventing and treating chronic infections. On the other hand, bacteria often have multiple molecular mechanisms to adapt to fluctuating environments. Understanding these mechanisms, and their redundancy, requires examinations in depth at the molecular level....

Mechanism and Function of Nascent Protein Modification in Bacteria

Chien-I Yang
Newly synthesized proteins undergo multiple modifications to ensure proper biogenesis and acquire their functions. N-terminal methionine excision (NME), mediated by the sequential actions of peptide deformylase (PDF) and methionine aminopeptidase (MAP), is an essential and the most prevalent N-terminal protein modification in the bacterial proteome. Despite the extensive studies on enzymatic catalysis, how NME impacts various cellular functions and how the enzymes achieve timing and selectivity under complex cellular conditions have been long-standing puzzles. In...

From Building Blocks to Theories: EFThedron and a Haagerup TFT

Tzu-Chen Huang
This thesis is dedicated to the study of certain building blocks of scattering amplitudes in (3+1)d Minkowskian spacetime and that of topological field theory in (1+1)d, together with the constraints which result from the properties of these building blocks. The first part of the thesis is concerned with the introduction of an on-shell formalism for massless and massive particles. We identify all possible three-point tensor structures compatible with the little group symmetry and overall mass...

The Chemistry of Europa and Venus, and Characterization of Earth-like Exoplanets

Jiazheng Li
This thesis contains three parts of work, including oxidant sources on Europa, sulfur chemistry on Venus, and the characterization of Earth-like exoplanets. In the first part, we build two chemical-transport models to study the various oxidant-generation processes that occur in both Europa’s atmosphere and surface ice. The atmospheric model focuses on the role that water plumes play in the formation of Europa’s ionosphere. The simulation results, which show that the ionization reactions are initiated by...

New-to-Nature Selective C-H Alkylation Using Engineered Carbene Transferases

Juner Zhang
Synthetic methods to selectively convert C–H bonds, a prevalent motif in organic molecules, into functionalities can significantly accelerate the syntheses and derivatization of molecules. In the past decade, many enzymatic catalysts have emerged as greener, more selective, and more versatile alternatives to small-molecule catalysts for selective C–H functionalization reactions. In nature, enzymes only catalyze a limited set of C–H functionalization reactions that are useful for chemical synthesis, as the overwhelming majority of known C–H functionalization...

Analytical Chemistry Investigations Toward Understanding the Mechanism of Nitrogenase from Azotobacter vinelandii and the Role of the 4Fe-4S Cluster of Dna2 from Saccharomyces cerevisiae

Siobhán Gaustad MacArdle
Iron sulfur clusters are ubiquitous metal cofactors that play a variety of roles in many enzymes important for health and the climate. The bacterial nitrogenase enzyme, which supports the growth of all organisms by converting atmospheric dinitrogen into ammonia, contains three different redox-active iron sulfur clusters that are central to its function. Dna2, found in all eukaryotes, is integral to genome maintenance and coordinates an iron sulfur cluster of unknown function. Many details of the...

A Multi-Disciplinary Approach: How Aqueous Minerals Hold the Key to Understanding the Climate and Habitability of Terrestrial Planets

Eva L. Scheller
Understanding the interplay between geological processes and the climate within the ancient pasts of terrestrial planets holds the key to deciphering what makes terrestrial planets habitable. The climates of both Mars and Earth were drastically different in their ancient pasts. Liquid water once flowed on Mars ~3-4 Ga, creating fluvial valleys and aqueous minerals, until Mars dried out to the desert planet we know today. During the Pleistocene (~ 2.6 Ma – 11.7 ka) and...

Theory of Mathematical Optimization for Delegated Portfolio Management

Zijian Tao
We study the optimization problem of finding closed convex sets Γ ⊆ Rd containing the origin that minimize F(Γ) = ∑i=1k wi | θi/2 - pΓ(θi) | 2, where w1, ..., wk > 0, θ1, ..., θk in Rd are given, and pΓ(θi) are the closest points in Γ to θi, i = 1, ..., k. This problem is motivated by the topic of delegated portfolio management in finance. In Chapter 2, we will explore...

Between Seismic Speed and Glacial Pace: Cryoseismic Observation of Intermediate-Scale Processes at Lemon Creek Glacier, Alaska

Celeste Ritter Labedz
In this thesis, I present three studies in environmental seismology. First, I present an analysis of seismic tremor generated from subglacial water flow during the rapid drainage of an ice-marginal supraglacial lake, collected by an on-ice nodal seismic array. I find that seismic tremor indicates a partial pressurization of the subglacial hydrologic system that was not accompanied by the expected change in glacier surface velocity, suggesting that factors like glacier geometry play a significant role...

Felt, Imagined, and Seen Touch Share A Substrate in Human Posterior Parietal Cortex

Srinivas Chivukula
One of the most remarkable aspects of human cognition is its flexibility. We can think new thoughts, infer meaning, plan actions, predict, extrapolate, and so much more. How do our brains enable this versatility? A growing ability to simultaneously record from large populations of single neurons in human cortex has begun to provide insight. Recent studies have identified that shared populations of neurons in posterior parietal cortex (PPC) of a human subject (involved in a...

Microwave-to-Optical Transduction Using Rare-Earth Ions

Jake Herschel Lebi Rochman
Superconducting qubits that operate at microwave frequencies are one of the most promising platforms for quantum information processing. However, connecting distant processors with microwave photons is challenging since microwave photons suffer from thermal noise and large propagation losses in room temperature components. Conversely, optical photons within the telecommunications band are known to have extremely low loss in optical fiber and the thermal noise is minuscule at room temperature. In order to interface superconducting qubits with...

Structural Basis of Antibody Recognition of Viruses

Shannon Esswein
The Zika epidemic in 2015-2016 and COVID-19 pandemic in 2019-2021 are the latest reminders of the enormous impact of viruses on the world. Zika, a flavivirus transmitted by mosquitos, can cause severe neurodevelopmental abnormalities including microcephaly in the newborns of the infected mothers. Vaccine design is complicated by concern that elicited antibodies may also recognize other epidemic-causing flaviviruses that share a similar envelope protein, such as dengue virus, West Nile Virus, and yellow fever virus....

The Development of the Research Journal and the Prehistory of Peer Review in the Philosophical Transactions of the Royal Society

Elia Gorokhovsky
[Introduction] Modern science descends primarily from the ancient Greeks, when the body of scientific knowledge was small enough that they were able to favor the oral method of passing on knowledge. As the need for international scientific communication expanded, alternate methods of communicating science arose. The development of European public postal networks starting in the fifteenth century allowed communication by letter between scientists. Long-distance correspondence networks allowed researchers to share short-form information or solicit feedback....

Strategies and Tools for Machine Learning-Assisted Protein Engineering

Bruce James Wittmann
Proteins perform critical roles in a growing list of human-devised applications, and as demands for new applications arise, new proteins must be engineered to meet them. Machine learning-assisted protein engineering (MLPE) has recently arisen as a new philosophy of protein engineering, promising to overcome many of the limitations of existing engineering strategies. Despite its promise, however, as a relatively new approach to protein engineering, MLPE faces many challenges that hinder its routine application. This thesis...

Nonlinear Dynamics and Stability of Viscous Free-Surface Microcapillary Flows in V-Shaped Channels and on Curved Surfaces

Nicholas C. White
The last two decades have brought a revolution in miniaturization of space technology. Thanks to improved microelectronic sensors and MEMS devices, nanosatellites can perform communication and scientific studies previously limited to large satellites, significantly reducing the financial barriers to space access. But development of a reliable, long-running, small-scale propulsion system for orbital maneuvers remains a key challenge. One solution is the microfluidic electrospray propulsion (MEP) thruster under development at NASA's Jet Propulsion Laboratory (JPL). This...

Interface Optimization for Improved Photovoltaic Devices

Rebecca Denise Glaudell
The wide band gaps and superior conductivity of ZnSₓSe₁₋ₓ semiconductors to amorphous Si suggest an alternative carrier-selective contact in silicon heterojunction solar cells. Electron-selective ZnSₓSe₁₋ₓ front contacts on p-type c-Si solar cells are explored by simulating in Sentaurus TCAD a large design parameter space informed by experimentally determined optoelectronic properties. Comparable performance to experimental and simulated p-SHJ reference devices is shown, with a champion simulated device efficiency of 20.8%. X-ray photoelectron spectroscopy is used to...

Registration Year

  • 2022

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  • California Institute of Technology
  • California Institute of Technology, Pasadena, CA (US)
  • 25
  • Jet Propulsion Lab
  • Jet Propulsion Laboratory, Pasadena, CA (US)
  • Harvard University, Cambridge, MA (US)
  • Earth and Space Sciences, University of Washington
  • Institute for Geophysics, Jackson School of Geosciences, University of Texas
  • Istituto Nazionale di Geofisica e Vulcanologia
  • NASA Wallops Flight Facility