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  1. Free, publicly-accessible full text available June 20, 2023
  2. Photoswitches are molecules that undergo a reversible, structural isomerization after exposure to different wavelengths of light. The dynamic control offered by molecular photoswitches is favorable for applications in materials chemistry, photopharmacology, and catalysis. Ideal photoswitches absorb visible light and have long-lived metastable isomers. We used high throughput virtual screening to predict the absorption maxima (λmax) of the E-isomer and half-lives (t1/2) of the Z-isomer. However, computing the photophysical and kinetic properties of each entry of a virtual molecular library containing 103–106 entries with density functional theory is prohibitively time-consuming. We applied active search, a machine learning technique to intelligently search a chemical search space of 255991 photoswitches based on 29 known azoarenes and their derivatives. We iteratively trained the active search algorithm based on whether a candidate absorbed visible light (λmax > 450 nm). Active search was found to triple the discovery rate compared to random search. Further, we projected 1962 photoswitches to 2D using the Uniform Manifold Approximation and Projection (umap) algorithm and found that λmax depends on the core, which is tunable with substituents. We then incorporated a second stage of screening with to predict the stabilities of the Z-isomers for the top 1% of candidates. We identifiedmore »four ideal photoswitches that concurrently satisfy λmax > 450 nm and t1/2 > 2 hours; the range of λmax and t1/2 range from 465 to 531 nm and hours to years, respectively.« less
  3. Gaur, L. ; Solanki, A. ; Jain, V. ; Khazanchi, D. (Ed.)
    This chapter extends application of a framework proposed by the authors (73, 74) for automated damage detection using strain measurements to study feasibility of using sensors that can measure accelerations, tilts, and displacements. The study utilized three-dimensional (3D) finite element models of double track, riveted, steel truss span, and girder bridge span under routine train loads. The chapter also includes three instrumentation schemes for each bridge span (65) to investigate the applicability of the framework to other bridge systems and sensor networks. Connection damage was simulated by reducing rotational spring stiffness at member ends and various responses were extracted for each damage scenario. The methodology utilizes Supervised Machine Learning to automatically determine damage location (DL) and intensity (DI). Simulated experiments showed that DLs and DIs were detected accurately for both spans with various structural responses and using different instrumentation plans.
  4. ABSTRACT

    We investigate the abundance and distribution of metals in the high-redshift intergalactic medium and circum-galactic medium through the analysis of a sample of almost 600 Si iv absorption lines detected in high- and intermediate-resolution spectra of 147 quasars. The evolution of the number density of Si iv lines, the column density distribution function, and the cosmic mass density are studied in the redshift interval 1.7 ≲ z ≲ 6.2 and for log N(Si iv) ≥ 12.5. All quantities show a rapid increase between z ∼ 6 and z ≲ 5 and then an almost constant behaviour to z ∼ 2 in very good agreement with what is already observed for C iv absorption lines. The present results are challenging for numerical simulations: When simulations reproduce our Si iv results, they tend to underpredict the properties of C iv, and when the properties of C iv are reproduced, the number of strong Si iv lines [log N(Si iv) > 14] is overpredicted.

  5. This paper seeks to illustrate the first steps in a process of adapting an existing, valid, and reliable spatial ability instrument – the Mental Cutting Test (MCT) – to assess spatial ability among blind and low vision (BLV) populations. To adapt the instrument, the team is developing three-dimensional (3-D) models of existing MCT questions such that a BLV population may perceive the test tactilely with their hands. This paper focuses on the development of the Tactile MCT (TMCT) instrument and does not report on the use of or results from the new instrument. Future work will investigate the validity and reliability of the adapted instrument. Each TMCT question is created by modeling and 3-D printing the objects represented by two-dimensional pictorial drawings on the MCT. The 3-D models of 25 items of the MCT are created using a solid modeling process followed by an additive 3-D printing process. The correct answer to each MCT question is the section view defined by a plane-of-interest (POI) intersecting the figure in question. A thin plane extending from the figure identifies the POI of each problem. The possible answers were originally presented in multiple representations including 3-D printed extrusions on top of a thinmore »plate, and two forms of tactile graphics. The 3-D printed answers are developed by a combination of acquiring accurate dimensions of the 3-D figure’s cross-section and scaling up the printed paper test. To improve this adaptation of the MCT instrument, the TMCT models and their respective multiple-choice answers will be inspected by a spatial cognition expert as well as several BLV individuals. Feedback from these individuals will provide insight into necessary revisions before the test is implemented.« less
  6. Abstract The accurate simulation of additional interactions at the ATLAS experiment for the analysis of proton–proton collisions delivered by the Large Hadron Collider presents a significant challenge to the computing resources. During the LHC Run 2 (2015–2018), there were up to 70 inelastic interactions per bunch crossing, which need to be accounted for in Monte Carlo (MC) production. In this document, a new method to account for these additional interactions in the simulation chain is described. Instead of sampling the inelastic interactions and adding their energy deposits to a hard-scatter interaction one-by-one, the inelastic interactions are presampled, independent of the hard scatter, and stored as combined events. Consequently, for each hard-scatter interaction, only one such presampled event needs to be added as part of the simulation chain. For the Run 2 simulation chain, with an average of 35 interactions per bunch crossing, this new method provides a substantial reduction in MC production CPU needs of around 20%, while reproducing the properties of the reconstructed quantities relevant for physics analyses with good accuracy.
    Free, publicly-accessible full text available December 1, 2023
  7. Free, publicly-accessible full text available November 1, 2023