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Physics-based, atom-centered machine learning (ML) representations have been instrumental to the effective integration of ML within the atomistic simulation community. Many of these representations build off the idea of atoms as having spherical, or isotropic, interactions. In many communities, there is often a need to represent groups of atoms, either to increase the computational efficiency of simulation via coarse-graining or to understand molecular influences on system behavior. In such cases, atom-centered representations will have limited utility, as groups of atoms may not be well-approximated as spheres. In this work, we extend the popular Smooth Overlap of Atomic Positions (SOAP) ML representation for systems consisting of non-spherical anisotropic particles or clusters of atoms. We show the power of this anisotropic extension of SOAP, which we deem AniSOAP, in accurately characterizing liquid crystal systems and predicting the energetics of Gay–Berne ellipsoids and coarse-grained benzene crystals. With our study of these prototypical anisotropic systems, we derive fundamental insights on how molecular shape influences mesoscale behavior and explain how to reincorporate important atom–atom interactions typically not captured by coarse-grained models. Moving forward, we propose AniSOAP as a flexible, unified framework for coarse-graining in complex, multiscale simulation. 

The latest generation of high-resolution spectrographs on 10m-class telescopes are designed to pursue challenging science cases. Consequently, ever more precise calibration methods are necessary to enable trail-blazing science methodology. We present the High-Resolution Infrared SPectrograph for Exoplanet Characterization (HISPEC) Calibration Unit (CAL), designed to facilitate challenging science cases such as Doppler imaging of exoplanet atmospheres, precision radial velocity, and high-contrast, high-resolution spectroscopy of nearby exoplanets. CAL builds on the heritage of the pathfinder instrument, the Keck Planet Imager and Characterizer (KPIC)1–3 and utilizes four near-infrared (NIR) light sources encoded with wavelength information that are coupled into singlemode fibers. They can be used synchronously during science observations or asynchronously during daytime calibrations. A uranium hollow cathode lamp (HCL) and a series of gas cells provide absolute calibration from 0.98 μm to 2.46 μm. Two laser frequency combs (LFC) provide stable, time-independent wavelength information during observation, and CAL implements two low-finesse Fabry-Perot etalons as a complement to the LFCs. 

Abstract Microplastics (MPs) are an emerging class of pollutants in air, soil and especially in all aquatic environments. Secondary MPs are generated in the environment during fragmentation of especially photo-oxidised plastic litter. Photo-oxidation is mediated primarily by solar UV radiation. The implementation of the Montreal Protocol and its Amendments, which have resulted in controlling the tropospheric UV-B (280–315 nm) radiation load, is therefore pertinent to the fate of environmental plastic debris. Due to the Montreal Protocol high amounts of solar UV-B radiation at the Earth’s surface have been avoided, retarding the oxidative fragmentation of plastic debris, leading to a slower generation and accumulation of MPs in the environment. Quantifying the impact of the Montreal Protocol in reducing the abundance of MPs in the environment, however, is complicated as the role of potential mechanical fragmentation of plastics under environmental mechanical stresses is poorly understood. 

Abstract Variations in stratospheric ozone and changes in the aquatic environment by climate change and human activity are modifying the exposure of aquatic ecosystems to UV radiation. These shifts in exposure have consequences for the distributions of species, biogeochemical cycles, and services provided by aquatic ecosystems. This Quadrennial Assessment presents the latest knowledge on the multi-faceted interactions between the effects of UV irradiation and climate change, and other anthropogenic activities, and how these conditions are changing aquatic ecosystems. Climate change results in variations in the depth of mixing, the thickness of ice cover, the duration of ice-free conditions and inputs of dissolved organic matter, all of which can either increase or decrease exposure to UV radiation. Anthropogenic activities release oil, UV filters in sunscreens, and microplastics into the aquatic environment that are then modified by UV radiation, frequently amplifying adverse effects on aquatic organisms and their environments. The impacts of these changes in combination with factors such as warming and ocean acidification are considered for aquatic micro-organisms, macroalgae, plants, and animals (floating, swimming, and attached). Minimising the disruptive consequences of these effects on critical services provided by the world’s rivers, lakes and oceans (freshwater supply, recreation, transport, and food security) will not only require continued adherence to the Montreal Protocol but also a wider inclusion of solar UV radiation and its effects in studies and/or models of aquatic ecosystems under conditions of the future global climate. Graphical abstract 

Abstract This manuscript describes the synthesis and characterization of guanine and cytosine‐containing supramolecular copolymers, which are inspired from the guanine and cytosine nucleobase pair in deoxyribonucleic acid. Regioselective Michael‐addition allowed the efficient installation of the nucleobases on acrylate‐containing monomers, which enabled the preparation of a series of nucleobase‐functionalized acrylate andn‐butyl acrylate copolymers using conventional free radical copolymerization. Guanine‐containing copolymers exhibited superior thermal properties, thermomechanical performance, and more defined morphological structure than cytosine‐containing copolymer analogs due to the relatively strong guanine self‐association, thus expanding the potential applications for mechanically reinforced polymeric networks. Blending guanine‐ and cytosine‐containing copolymers formed a supramolecular structure through multiple hydrogen bonding between guanine and cytosine units. The supramolecular blend exhibited intermediate thermomechanical and morphological properties, which suggested that guanine and cytosine units were not fully associated in the random copolymer composition. This work provides valuable fundamental understanding of structure–property‐morphology relationships in acrylic copolymers with the presence of guanine‐cytosine self‐ and complementary interactions, suggesting new understanding in supramolecular design for enhanced mechanical and morphological properties. 

Abstract Mount Michael stratovolcano, South Sandwich Islands is extremely remote and challenging to observe, but eruptive activity has been sporadically observed since 1820 and captured by satellite methods since 1989. We identify long‐range infrasound signals recorded by the International Monitoring System attributable to episodes of persistent eruptive activity at Mount Michael. Analysis of multi‐year (2004–2020) infrasound array data at station IS27, Antarctica (range 1,672 km) reveals candidate signals especially from May 2005 to January 2008 and from May 2016 to April 2018. By combining ray‐tracing with empirical climatologies and atmospheric specifications, we show that systematic variations in the observed backazimuth of the signals (at IS27) are broadly consistent with annual variability in stratospheric propagation conditions for a source at Mount Michael. Observed signal amplitudes combined with transmission loss estimates are consistent with moderate explosive eruption. We highlight a selection of infrasound signals that correspond to satellite observation of eruptions. 

Abstract The Environmental Effects Assessment Panel of the Montreal Protocol under the United Nations Environment Programme evaluates effects on the environment and human health that arise from changes in the stratospheric ozone layer and concomitant variations in ultraviolet (UV) radiation at the Earth’s surface. The current update is based on scientific advances that have accumulated since our last assessment (Photochem and Photobiol Sci 20(1):1–67, 2021). We also discuss how climate change affects stratospheric ozone depletion and ultraviolet radiation, and how stratospheric ozone depletion affects climate change. The resulting interlinking effects of stratospheric ozone depletion, UV radiation, and climate change are assessed in terms of air quality, carbon sinks, ecosystems, human health, and natural and synthetic materials. We further highlight potential impacts on the biosphere from extreme climate events that are occurring with increasing frequency as a consequence of climate change. These and other interactive effects are examined with respect to the benefits that the Montreal Protocol and its Amendments are providing to life on Earth by controlling the production of various substances that contribute to both stratospheric ozone depletion and climate change.