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The Languages of Early Medieval Charters: Latin, Germanic Vernaculars, and the Written Word [Book Review]
No full textThis volume collects a set of essays dealing with the interplay between Latin and the vernacular languages in parts of early medieval Europe where the vernaculars were not Romance, but rather (for the most part) Germanic: eastern Francia and Anglo-Saxon England
Reports From The Frontier-Heterogeneous Electrocatalysts for Sustainable Electrochemical Synthesis
No full textOne key strategy toward decarbonizing chemical synthesis is to reduce reliance on fossil fuels as an energy source. The increased availability of renewable electricity from sources such as solar and wind offers opportunities to both reduce reliance on fossil fuels and electrify chemical manufacturing. While there are many possible uses for renewable electricity, such as joule heating of reactors, one approach is to use these electrons to make and break chemical bonds directly via electrochemistry
Predicting the seismic behavior of multiblock tower structures using the level set discrete element method
No full textIn this paper a modeling method is validated at multiple scales for the seismic performance of multiblock tower structure (MTS). MTS are a proposed concept for large-capacity gravitational energy storage that will enable renewable energy sources. The structure modeled is a tower of 7144 nominally identical blocks arranged in a 38-layered annular pattern with no adhesive mechanisms between the blocks or the blocks and the foundation. The level set discrete element method is used to model the dynamics of the tower structure experiencing a ground motion. Experimental determination of each model parameter is shown from the use of individual blocks before construction. Close comparisons to experimental results are shown for the dynamic motion of the tower over a full ground motion time history for multiple scales, materials and ground motions. When the tower was brought to failure, the two ground motions used produced distinct failure modes of the tower showing both a peeling and buckling behavior. Both the effect of the friction coefficient and unequal block heights are investigated. Friction coefficient has a noticeable effect on the amplitude of motion of the tower while the unevenness of the block heights affects mostly the structural speed
Stomatal responses of terrestrial plants to global change
No full textQuantifying the stomatal responses of plants to global change factors is crucial for modeling terrestrial carbon and water cycles. Here we synthesize worldwide experimental data to show that stomatal conductance (gₛ) decreases with elevated carbon dioxide (CO₂), warming, decreased precipitation, and tropospheric ozone pollution, but increases with increased precipitation and nitrogen (N) deposition. These responses vary with treatment magnitude, plant attributes (ambient gₛ, vegetation biomes, and plant functional types), and climate. All two-factor combinations (except warming + N deposition) significantly reduce gₛ, and their individual effects are commonly additive but tend to be antagonistic as the effect sizes increased. We further show that rising CO₂ and warming would dominate the future change of plant gₛ across biomes. The results of our meta-analysis provide a foundation for understanding and predicting plant gₛ across biomes and guiding manipulative experiment designs in a real world where global change factors do not occur in isolation
Dodecamer assembly of a metazoan AAA⁺ chaperone couples substrate extraction to refolding
No full textRing-forming AAA⁺ chaperones solubilize protein aggregates and protect organisms from proteostatic stress. In metazoans, the AAA⁺ chaperone Skd3 in the mitochondrial intermembrane space (IMS) is critical for human health and efficiently refolds aggregated proteins, but its underlying mechanism is poorly understood. Here, we show that Skd3 harbors both disaggregase and protein refolding activities enabled by distinct assembly states. High-resolution structures of Skd3 hexamers in distinct conformations capture ratchet-like motions that mediate substrate extraction. Unlike previously described disaggregases, Skd3 hexamers further assemble into dodecameric cages in which solubilized substrate proteins can attain near-native states. Skd3 mutants defective in dodecamer assembly retain disaggregase activity but are impaired in client refolding, linking the disaggregase and refolding activities to the hexameric and dodecameric states of Skd3, respectively. We suggest that Skd3 is a combined disaggregase and foldase, and this property is particularly suited to meet the complex proteostatic demands in the mitochondrial IMS
Rhodium-Catalyzed Alkenylation of Arenes with Multi-Substituted Olefins: Comparison of Selectivity and Reaction Rate as a Function of Olefin Identity
No full textRhodium-catalyzed arene alkenylation using Cu(II) carboxylates as the in situ oxidant and mono-substituted olefins has been previously reported (e.g., J. Am. Chem. Soc. 2019, 139, 5474; J. Am. Chem. Soc. 2018, 140, 17007; Organometallics 2019, 38, 3860; J. Am. Chem. Soc. 2020, 142, 10534). Herein, studies are extended to multi-substituted olefins with the goal of evaluating the effect of olefin substitution pattern and substituent identity on selectivity and turnover frequency. The influence of olefin substitution is probed by comparing the conversion of benzene to alkenyl arenes with ethylene, propylene, 1-butene, cis-2-butene, trans-2-butene, isobutene, 2-methyl-2-butene, and tetramethylethylene as well as the phenyl-substituted olefins and isomers of propenylbenzene. The rate of oxidative hydrophenylation for multi-substituted olefins follows the trend monosubstituted > disubstituted > trisubstituted, and tetrasubstituted olefins are unreactive. To probe the effect of substituent size on Markovnikov/anti-Markovnikov regioselectivity, cyclohexyl, tert-butyl, isopropyl, ethyl, and methyl substituted α-olefins are compared. Selectivity for anti-Markovnikov products generally increases as substituent steric bulk is increased. Tolerance for some functionalized olefins is demonstrated. The ortho/meta/para regioselectivity with mono-substituted arenes reveals that arene and olefin identity influences selectivity. Further mechanistic studies provide evidence for Curtin–Hammet control of ortho/meta/para regioselectivity with monosubstituted arenes
A temperate Earth-sized planet with tidal heating transiting an M6 star
No full textTemperate Earth-sized exoplanets around late-M dwarfs offer a rare opportunity to explore under which conditions planets can develop hospitable climate conditions. The small stellar radius amplifies the atmospheric transit signature, making even compact secondary atmospheres dominated by N₂ or CO₂ amenable to characterization with existing instrumentation. Yet, despite large planet search efforts, detection of low-temperature Earth-sized planets around late-M dwarfs has remained rare and the TRAPPIST-1 system, a resonance chain of rocky planets with seemingly identical compositions, has not yet shown any evidence of volatiles in the system. Here we report the discovery of a temperate Earth-sized planet orbiting the cool M6 dwarf LP 791-18. The newly discovered planet, LP 791-18d, has a radius of 1.03 ± 0.04 R_⊕ and an equilibrium temperature of 300–400 K, with the permanent night side plausibly allowing for water condensation. LP 791-18d is part of a coplanar system4 and provides a so-far unique opportunity to investigate a temperate exo-Earth in a system with a sub-Neptune that retained its gas or volatile envelope. On the basis of observations of transit timing variations, we find a mass of 7.1 ± 0.7 M_⊕ for the sub-Neptune LP 791-18c and a mass of 0.9^(+0.5)_(−0.4) M_⊕
for the exo-Earth LP 791-18d. The gravitational interaction with the sub-Neptune prevents the complete circularization of LP 791-18d’s orbit, resulting in continued tidal heating of LP 791-18d’s interior and probably strong volcanic activity at the surface
Value-based neural representations predict social decision preferences
No full textSocial decision-making is omnipresent in everyday life, carrying the potential for both positive and negative consequences for the decision-maker and those closest to them. While evidence suggests that decision-makers use value-based heuristics to guide choice behavior, very little is known about how decision-makers’ representations of other agents influence social choice behavior. We used multivariate pattern expression analyses on fMRI data to understand how value-based processes shape neural representations of those affected by one’s social decisions and whether value-based encoding is associated with social decision preferences. We found that stronger value-based encoding of a given close other (e.g. parent) relative to a second close other (e.g. friend) was associated with a greater propensity to favor the former during subsequent social decision-making. These results are the first to our knowledge to explicitly show that value-based processes affect decision behavior via representations of close others
Ultra wide‐field infrared astronomy in Antarctica
No full textThe science enabled by the deep and high-cadence survey that will be performed by the Vera Rubin Observatory has led to an increase of survey and follow-up capabilities around the world. The infrared, has however, not match this growth due to the challenges caused by the atmospheric and the cost of large detector arrays. In this paper, we present solutions to resolve these challenges and a path toward an Antarctic observatory capable matching the volumetric speed of the Vera Rubin Observatory survey in the infrared k-band. We will detail the current state of infrared survey telescopes, demonstrate the benefits of Antarctic high-plateau for such observations, and show some of the development made in detector technologies to make large detector arrays a reality for such application
Hubble Space Telescope Proper Motion Measurements of Supernova Remnant N132D: Center of Expansion and Age
No full textWe present proper motion measurements of the oxygen-rich ejecta of the LMC supernova remnant N132D using two epochs of Hubble Space Telescope Advanced Camera for Surveys data spanning 16 years. The proper motions of 120 individual knots of oxygen-rich gas were measured and used to calculate a center of expansion (CoE) of α = 5h25m01 71 and δ = −69°38'41 64 (J2000) with a 1σ uncertainty of 2.”90. This new CoE measurement is 9.”2 and 10.”8 from two previous CoE estimates based on the geometry of the optically emitting ejecta. We also derive an explosion age of 2770 ± 500 yr, which is consistent with recent age estimates of ≈2500 yr made from 3D ejecta reconstructions. We verified our estimates of the CoE and age using a new automated procedure that detected and tracked the proper motions of 137 knots, with 73 knots that overlap with the visually identified knots. We find that the proper motions of the ejecta are still ballistic, despite the remnant's age, and are consistent with the notion that the ejecta are expanding into an interstellar medium cavity. Evidence for explosion asymmetry from the parent supernova is also observed. Using the visually measured proper motion measurements and corresponding CoE and age, we compare N132D to other supernova remnants with proper motion ejecta studies