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Abstract Holsnøy, Norway, offers a world-class natural laboratory for studying the impact of fluid on subducting lower crust. Holsnøy is composed of dry, metastable lower crustal granulite that was infiltrated by fluids along shear zones and seismic fractures during subduction. The infiltration facilitated the localized growth of eclogite facies mineral assemblages along the fluid flow pathways. The duration of the eclogite facies metamorphism, however, remains uncertain. Previous garnet diffusion chronometry studies have estimated timescales ranging from hundreds of years to millions of years based on diffusional relaxation between metastable granulite facies garnet cores and eclogite facies garnet rims and fractures. The shorter timescales are inferred from extremely sharp Ca gradients across chemical contacts present in some garnets whereas the longer timescales are from wider Mg and Fe profiles present in all garnets. The different timescale estimates have led to divergent models for the region’s tectonometamorphic evolution. Here we show that the sharp Ca contacts can be explained by diffusion-induced compositional stress. As Ca is significantly larger than Mg and Fe, its movement strains the crystal lattice and generates stress that limits the relaxation of sharp chemical contacts. When compositional stress is accounted for, the sharp contacts yield timescales that are consistent with the wider Mg and Fe diffusion profiles. We determine that eclogite facies conditions (670–700 °C, 1.5–2.2 GPa) lasted a maximum of c. 300 kyr. The relatively short duration of eclogite facies conditions requires that multiple transient heating events were superimposed on a longer (>106 yr) overall timescale of metamorphism. Granulite facies garnet cores are surrounded by multiple generations of eclogite facies rims formed by interface-coupled dissolution–reprecipitation (ICDR) reactions. The garnet rims indicate two rapid, regional-scale fluid pulses and additional smaller, more localized pulses. The fluid pulses may be linked to episodes of seismic moment release as well as transient heating via exothermic hydration reactions and/or shear deformation. Our model results predict up to 400 MPa of differential stress at the garnet core–rim contacts, consistent with observed eclogite facies microfractures that extend into relic granulite facies garnet cores. The microfractures indicate that ICDR was aided by compositional stress: diffusion ahead of the reaction front generated stress and fracturing that created porosity for further ICDR. Thus, compositional stress can markedly impact both diffusion systematics and intracrystalline deformation. Together, these results show that despite their brevity, transient thermal, fluid flux, and/or baric episodes may exert the primary controls on the mineralogical and rheological development of subducted lithologies, in contrast to the long, slow burial and exhumation typically envisioned for regional metamorphism. 

Sheet Molding Compound (SMC) is a widely used composite material, particularly in automotive applications, due to its cost-effectiveness, lightweight properties, and adaptability for complex shapes. While E-glass is commonly used as reinforcement in SMC, its strength and stiffness are limited compared to carbon fiber (CF). Previous research has focused on continuous-discontinuous SMC hybrids, combining continuous CF with glass fiber substrates, but these approaches are costly and complex to manufacture. This study explores a novel discontinuous-discontinuous hybrid SMC that combines E-glass SMC (G-SMC) with recycled carbon fiber (rCF) mats, aiming to enhance mechanical properties without a significant cost increase. Two materials were produced, one with and one without rCF, and were tested for flexural, tensile, interlaminar shear, and impact properties. Failure mechanisms were also examined through digital imaging. This approach demonstrates the potential for a cost-effective and practical SMC hybrid suitable for commercial applications in the automotive industry. 

Abstract The catalytic performance of enzymes is largely perceived to be a property of the enzyme itself, altered by environmental conditions, such as temperature and pH. However, the maximal catalytic rates of enzymes differ up to 100-fold between in vivo and in vitro measurements, suggesting that a complex chemical system has additional effects on catalytic performance. In this work, we show that the initial rate of an enzyme can increase 3-fold due to the presence of a second enzyme, which uses the product of the first enzyme as its substrate. This enhancement may originate in an allosteric effect or result from binding competition for the product molecule by the second enzyme. 

Abstract OH megamasers (OHMs) are extragalactic masers found primarily in gas-rich galaxy major mergers. To date, only ∼120 OHMs have been cataloged since their discovery in 1982, and efforts to identify distinct characteristics of OHM host galaxies have remained inconclusive. As radio astronomy advances with next-generation telescopes and extensive 21 cm Hisurveys, precursors to the Square Kilometre Array are expected to detect the 18 cm OH masing line with significantly increased frequency, potentially expanding the known OHM population tenfold. These detections, however, risk confusion with lower-redshift Hiemitters unless accompanied by independent spectroscopic redshifts. Building on methods proposed by Roberts et al. for distinguishing these interloping OHMs via near- to mid-IR photometry and emission line frequencies, we apply these techniques to data from the Arecibo Legacy Fast ALFA [AreciboL-band Feed Array] (ALFALFA) survey and a preliminary Aperture Tile In Focus (Apertif) Hiemission line catalog from the Westerbork Synthesis Radio Telescope. Our study, utilizing the Apache Point Observatory 3.5 m telescope to obtain optical spectroscopic redshifts of 142 candidates (107 from ALFALFA and 35 from Apertif), confirms five new OHM host galaxies and reidentifies two previously catalogued OHMs misclassified as Hiemitters in ALFALFA. These findings support the predictions from Roberts et al. and underscore the evolving landscape of radio astronomy in the context of next-generation telescopes.