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We study the $\ell_p$ regression problem, which requires finding $\mathbf{x}\in\mathbb R^{d}$ that minimizes $\\mathbf{A}\mathbf{x}\mathbf{b}\_p$ for a matrix $\mathbf{A}\in\mathbb R^{n \times d}$ and response vector $\mathbf{b}\in\mathbb R^{n}$. There has been recent interest in developing subsampling methods for this problem that can outperform standard techniques when $n$ is very large. However, all known subsampling approaches have run time that depends exponentially on $p$, typically, $d^{\mathcal{O}(p)}$, which can be prohibitively expensive. We improve on this work by showing that for a large class of common \emph{structured matrices}, such as combinations of lowrank matrices, sparse matrices, and Vandermonde matrices, there are subsampling based methodsmore »Free, publiclyaccessible full text available April 25, 2023

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Ferroelectric nanomaterials offer the promise of switchable electronic properties at the surface, with implications for photo and electrocatalysis. Studies to date on the effect of ferroelectric surfaces in electrocatalysis have been primarily limited to nanoparticle systems where complex interfaces arise. Here, we use MBEgrown epitaxial BaTiO_{3 thin films with atomically sharp interfaces as model surfaces to demonstrate the effect of ferroelectric polarization on the electronic structure, intermediate binding energy, and electrochemical activity toward the hydrogen evolution reaction (HER). Surface spectroscopy and ab initio DFT +U calculations of the welldefined (001) surfaces indicate that an upward polarized surface reduces the workmore »function relative to downward polarization and leads to a smaller HER barrier, in agreement with the higher activity observed experimentally. Employing ferroelectric polarization to create multiple adsorbate interactions over a single electrocatalytic surface, as demonstrated in this work, may offer new opportunities for nanoscale catalysis design beyond traditional descriptors.« less}Free, publiclyaccessible full text available May 2, 2023

Extreme heat events induced by climate change present a growing risk to transit passenger comfort and health. To reduce exposure, agencies may consider changes to schedules that reduce headways on heavily trafficked bus routes serving vulnerable populations. This paper develops a schedule optimization model to minimize heat exposure and applies it to local bus services in Phoenix, Arizona, using agentbased simulation to inform travel demand and rider characteristics. Rerouting as little as 10% of a fleet is found to reduce networkwide exposure by as much as 35% when operating at maximum fleet capacity. Outcome improvements are notably characterized by diminishingmore »Free, publiclyaccessible full text available February 22, 2023

Abstract Convergence to equilibrium of underdamped Langevin dynamics is studied under general assumptions on the potential U allowing for singularities. By modifying the direct approach to convergence in L 2 pioneered by Hérau and developed by Dolbeault et al , we show that the dynamics converges exponentially fast to equilibrium in the topologies L 2 (d μ ) and L 2 ( W * d μ ), where μ denotes the invariant probability measure and W * is a suitable Lyapunov weight. In both norms, we make precise how the exponential convergence rate depends on the friction parameter γ in Langevin dynamics,more »Free, publiclyaccessible full text available December 29, 2022

Earis, Philip (Ed.)Perovskite photovoltaics (PVs) are under intensive development for promise in terrestrial energy production. Soon, the community will find out how much of that promise may become reality. Perovskites also open new opportunities for lower cost space power. However, radiation tolerance of space environments requires appropriate analysis of relevant devices irradiated under representative radiation conditions. We present guidelines designed to rigorously test the radiation tolerance of perovskite PVs. We review radiation conditions in common orbits, calculate nonionizing and ionizing energy losses (NIEL and IEL) for perovskites, and prioritize proton radiation for effective nuclear interactions. Lowenergy protons (0.05–0.15 MeV) create a representativemore »Free, publiclyaccessible full text available May 18, 2023

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We study stability of solutions for a randomly driven and degenerately damped version of the Lorenz ’63 model. Specifically, we prove that when damping is absent in one of the temperature components, the system possesses a unique invariant probability measure if and only if noise acts on the convection variable. On the other hand, if there is a positive growth term on the vertical temperature profile, we prove that there is no normalizable invariant state. Our approach relies on the derivation and analysis of nontrivial Lyapunov functions which ensure positive recurrence or nullrecurrence/transience of the dynamics.Free, publiclyaccessible full text available December 1, 2022

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