HOP Queue: Hyperspectral Onboard Processing Queue Demonstration

The HOP Queue (Hyperspectral Onboard Processing Queue) demonstration leverages emerging COTS AI accelerators and GPUs to perform on-board processing of hyperspectral imagery data, with the aim of providing near- real time conservation-oriented data and metrics from Low Earth Orbit (LEO). These include forest health, fire detection, and coastal water health. Phase 1 of this project is currently underway, including a completed lab demonstration of this technology and ongoing flight testing. The data from this mission will support Northrop Grumman’s enterprise “Technology for Conservation” campaign and will be provided to NASA’s Surface Biology and Geology (SBG) organization, as well as other conservation efforts

Light and Chemistry at the Interface of Theory and Experiment

Optics are a powerful probe of chemical structure that can often be linked to theoretical predictions, providing robustness as a measurement tool. Not only do optical interactions like second harmonic generation (SHG), single and two-photon excited fluorescence (TPEF), and infrared absorption provide chemical specificity at the molecular and macromolecular scale, but the ability to image enables mapping heterogeneous behavior across complex systems such as biological tissue. This thesis will discuss nonlinear and linear optics, leveraging theoretical predictions to provide frameworks for interpreting analytical measurement. In turn, the causal mechanistic understanding provided by these frameworks will enable structurally specific quantitative tools with a special emphasis on application in biological imaging. The thesis will begin with an introduction to 2nd order nonlinear optics and the polarization analysis thereof, covering both the Jones framework for polarization analysis and the design of experiment. Novel experimental architectures aimed at reducing 1/f noise in polarization analysis will be discussed, leveraging both rapid modulation in time through electro-optic modulators (Chapter 2), as well as fixed-optic spatial modulation approaches (Chapter 3). In addition, challenges in polarization-dependent imaging within turbid systems will be addressed with the discussion of a theoretical framework to model SHG occurring from unpolarized light (Chapter 4). The application of this framework to thick tissue imaging for analysis of collagen local structure can provide a method for characterizing changes in tissue morphology associated with some common cancers (Chapter 5). In addition to discussion of nonlinear optical phenomena, a novel mechanism for electric dipole allowed fluorescence-detected circular dichroism will be introduced (Chapter 6). Tackling challenges associated with label-free chemically specific imaging, the construction of a novel infrared hyperspectral microscope for chemical classification in complex mixtures will be presented (Chapter 7). The thesis will conclude with a discussion of the inherent disadvantages in taking the traditional paradigm of modeling and measuring chemistry separately and provide the multi-agent consensus equilibrium (MACE) framework as an alternative to the classic meet-in-the-middle approach (Chapter 8). Spanning topics from pure theoretical descriptions of light-matter interaction to full experimental work, this thesis aims to unify these two fronts

Connectivity-Based Biocompatible Force Field for Thiolated Gold Nanoclusters

Thiolated gold nanoclusters (AuNCs), sub-2 nm Au particles capped by Au­(I) thiolate complexes, promise to have a myriad of applications in biomedical diagnosis and therapy as well as industrial catalysis, energy production, and monitoring of environmental pollutants. Computational simulations are a valuable tool in elucidating design principles for optimizing application-specific physicochemical properties. However, thiolated AuNCs protected, conjugated, and/or interacting with macromolecules often exceed the limit of computational tractability with present-day quantum chemistry software. To facilitate theoretical studies, a molecular mechanics force field, AuSBio, is presented that reasonably reproduces, and retains, characteristic structural features of perhaps the most intensively studied thiolated AuNC, Au₂₅L₁₈ (L = alkylthiolate), over 2 ns finite temperature molecular dynamics simulations. AuSBio was parametrized within the framework of force fields for (bio)­organic simulations to reproduce equilibrium structures and the vibrational density of states for small homoleptic and larger thiolated Au clusters. AuSBio was further validated by the ability to reproduce the experimental structure of Au₃₈L₂₄, as well as bundling of long-chain alkylthiolate ligands, and the nonlinear frequency modulation pattern of a Raman-active vibrational mode, observed experimentally for the Au₂₅ cluster. We envision our AuSBio force field facilitating, in a practical manner, molecular mechanics or hybrid quantum/molecular mechanics simulations on the structure and dynamics of thiolated AuNC bioconjugates and AuNC monolayer-mediated molecular recognition and catalysis events