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George J. Nelson

Publications and source records attributed to George J. Nelson.

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Deep learning denoising unlocks quantitative insights in operando materials microscopy

Operando microscopy provides direct insight into the dynamic chemical and physical processes that govern functional materials, yet measurement noise limits the effective resolution and undermines quantitative analysis. Here, we present a general framework for integrating unsupervised deep learning-based denoising into quantitative microscopy workflows across modalities and length scales. Using simulated data, we demonstrate that deep denoising preserves physical fidelity, introduces minimal bias, and reduces uncertainty in model learning with partial differential equation (PDE)-constrained optimization. Applied to experiments, denoising reveals nanoscale chemical and structural heterogeneity in scanning transmission X-ray microscopy (STXM) of lithium iron phosphate (LFP), enables automated particle segmentation and phase classification in optical microscopy of graphite electrodes, and reduces noise-induced variability by nearly 80% in neutron radiography to resolve heterogeneous lithium transport. Collectively, these results establish deep denoising as a powerful, modality-agnostic enhancement that advances quantitative operando imaging and extends the reach of previously noise-limited techniques.

cs.CV

A Search for Gravitationally Lensed Quasars and Quasar Pairs in Pan-STARRS1: Spectroscopy and Sources of Shear in the Diamond 2M1134$-$2103

We present results of a systematic search for gravitationally lensed quasars in Pan-STARRS1. Our final sample of candidates comprises of 91 systems, not including 25 rediscovered lensed quasars and quasar pairs. In the absence of spectroscopy to verify the lensing nature of the candidates, the main sources of contaminants are likely to be quasar pairs, which we consider to be a byproduct of our work, and a smaller number of quasar$+$star associations. Amongst the independently discovered quads is 2M1134$-$2103, for which we obtained spectroscopy for the first time, finding a redshift of 2.77 for the quasar. There is evidence for microlensing in at least one image. We perform detailed mass modeling of this system using archival imaging data, and find that the unusually large shear responsible for the diamond-like configuration can be attributed mainly to a faint companion $\sim 4''$ away, and to a galaxy group/cluster $\sim 30''$ away. We also set limits of $z\sim0.5-1.5$ on the redshift of the lensing galaxy, based on its brightness, the image separation of the lensed images, and an analysis of the observed photometric flux ratios.

astro-ph.GA