California Institute of Technology

Interaction Potentials of Atom-Molecule and Molecule-Molecule Systems from Crossed Beam Experiments

The text of this thesis is comprised of eight chapters and six appendices. The first chapter is an introduction, overviewing the purpose of the experiments and outlining the remainder of the thesis. Chapters 2 and 3 survey the theory of intermolecular potentials and of elastic sc...

Studies of Magneto-Optically and Magnetostatically Trapped Cesium in a Cryogenic Vacuum Apparatus

The use of a cryogenic apparatus has several advantages for the magneto-optical and magnetostatic trapping of atoms. We have measured the lifetimes of magneto-optical and magnetostatic traps for cesium to be greatly increased in a cryogenic vacuum environment relative to a room-t...

Turing Pattern Formation in the Chlorine Dioxide-Iodine-Malonic Acid Reaction-Diffusion System

The formation of localized structures in the chlorine dioxide-idodine-malonic acid (CDIMA) reaction-diffusion system is investigated numerically using a realistic model of this system. We analyze the one-dimensional patterns formed along the gradients imposed by boundary feeds, a...

An AI-Assisted Workflow for Rapid Prioritization of FDA-Approved Drugs as HDAC3 Inhibitor Candidates for Drug Repurposing

Epigenetic regulation through histone acetylation plays a critical role in gene expression and cancer progression. Because of its pivotal role in chromatin remodeling, Histone deacetylase 3 (HDAC3) has become a promising therapeutic target. In this study, an artificial intelligen...

Category-Native Solomonoff Approximation: From Algorithmic Geometry to Kernels, Operators, and Induction

Solomonoff induction mixes all computable explanations with description-length weights, but it is incomputable. This theory-and-position paper argues that practical approximation must be category-native: one should first declare the mathematical category in which a computable sha...

Homogeneous Iron Porphyrin as a Molecular CO Shuttle Enables Electrochemical Multicarbon Product Formation from CO2

Abstract Homogeneous molecular catalysts for electrochemical CO2 reduction are generally limited to two-electron-reduced C1 products, primarily CO. Here we propose and demonstrate a fundamentally distinct role for molecular catalysts: as reversible CO shuttles that enhance the lo...

Slow Cosmic-Ray Diffusion in Supersonic and Super-Alfvénic Turbulence

Abstract Extended TeV–PeV gamma-ray halo observations imply cosmic-ray (CR) diffusion that is both substantially slower than the Galactic mean and only weakly anisotropic despite the presence of a large-scale Galactic magnetic field background. We investigate whether such transpo...

Reproducibility, Replicability, and Research Quality in Homogeneous Catalysis

Abstract Researchers from all sectors of homogeneous catalysis convened in response to concerns regarding reproducibility in science to analyze the issue and provide recommendations. In addition to an in-person workshop, the group engaged the broader homogeneous catalysis communi...

Quantum-well metasurface for free-space-accessible enhanced nonlinear polarization

Abstract Nonlinear frequency conversion underpins important technologies such as telecommunications and quantum computation; however, weak nonlinearities and architectures that resist miniaturization currently limit devices’ efficiency and widespread adoption. Here we combine a b...

Observations of Atmospheric Helium and Oxygen With SPHEREx

Abstract We present measurements of near‐infrared (NIR) terrestrial airglow produced by helium and oxygen in the exosphere as observed by the Spectro‐Photometer for the History of the Universe, Epoch of Reionization, and ices Explorer (SPHEREx). Using 8 months of survey data obta...

A large-scale integrated optical phased array with digital beamforming

Abstract Digital signal processing has driven much of the capacity growth in coherent fiber-optic communications, but its use in free-space coherent imagers and sensors has so far been limited. We report a 128-element optical phased array with a fully parallelized readout that pe...

Neural network–augmented Pfaffian wave-functions for scalable simulations of interacting fermions

Developing accurate numerical methods for strongly interacting fermions is crucial for improving our understanding of various quantum many-body phenomena, especially unconventional superconductivity. Recently, neural quantum states have emerged as a promising approach for studyin...

Spin-disc misalignment drives periodic accretion and pulse profile asymmetry in X-ray pulsars

Abstract We investigate magnetospheric accretion in disc-fed X-ray pulsars assuming that the neutron star spin axis is not perpendicular to the disc plane. We focus on X-ray pulsars, where a geometrically thin disc is truncated far from the stellar surface the channelled part of...

Video reconstruction of variable VLBI observations with neural fields

Abstract Supermassive black hole accretion and the ejection of collimated, relativistic jets of plasma are intrinsically dynamic processes shaped by large-scale magnetic fields 1–4 . Various algorithms have been developed to image these objects at different scales using radio int...

Redox-Dependent Lipophilicity of Phenazine Metabolites Is Modulated by Intramolecular Hydrogen Bonds and Controls Their Biological Distribution

Abstract Phenazines are redox-active microbial metabolites produced and secreted in diverse ecological contexts from soils to chronic infections. Phenazines can function variously as antibiotics, extracellular electron shuttles, and nutrient scavengers. Key to understanding the i...

Electronic Properties Associated with Donor Impurities in Multivalley Semiconductors

In this thesis we treat the theory of the electronic properties of excitons bound to a neutral donor in multivalley semiconductors. The materials considered here are Si, Ge and GaP. To deal with the effect of realistic band structures on the excitons bound to a neutral donor, we...

Little Red Dots host Black Hole Stars: A unified family of gas-reddened AGN revealed by JWST/NIRSpec spectroscopy

Abstract We construct and characterise a sample of 146 little red dots (LRDs) across 2.0 < z < 9.3, selecting all sources with v-shaped UV-optical continua from JWST NIRSpec/PRISM spectra and compact morphologies in NIRCam/F444W imaging. We show that LRD continuum spectra are wel...

The history of enzyme evolution embedded in metabolism.

Whereas phylogenetic reconstructions are a primary record of protein evolution, it is unknown whether the deep history of enzymes is encoded at higher levels of biological organization. Here, we demonstrate that the emergence and reuse history of enzymatic folds is embedded withi...

Morphogenesis of bacterial colonies in liquid crystalline environments

Natural bacterial habitats are often complex fluids with viscoelastic and anisotropic responses to stress; for example, they can take the form of liquid crystals (LCs), with elongated microscopic constituents that collectively align while still retaining the ability to flow. Howe...

Neural dynamics underlying minute-timescale persistent behaviour in the human brain

Pursuing longer-term goals relies on representations of task context that can be maintained over long periods of time and switched flexibly when goals change. Little is known about the neural substrate for maintaining context representations on the minute-timescale on which human...