Sulfur loss from subducted altered oceanic crust and implications for mantle oxidation

© The Author(s), [year]. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Walters, J. B., Cruz-Uribe, A. M., & Marschall, H. R. Sulfur loss from subducted altered oceanic crust and implications for mantle oxidation. Geochemical Perspectives Letters, 13, (2020): 36-41, doi:10.7185/geochemlet.2011.Oxygen fugacity (fO2) is a controlling factor of the physics of Earth’s mantle; however, the mechanisms driving spatial and secular changes in fO2 associated with convergent margins are highly debated. We present new thermodynamic models and petrographic observations to predict that oxidised sulfur species are produced during the subduction of altered oceanic crust. Sulfur loss from the subducting slab is a function of the protolith Fe3+/ΣFe ratio and subduction zone thermal structure, with elevated sulfur fluxes predicted for oxidised slabs in cold subduction zones. We also predict bi-modal release of sulfur-bearing fluids, with a low volume shallow flux of reduced sulfur followed by an enhanced deep flux of sulfate and sulfite species, consistent with oxidised arc magmas and associated copper porphyry deposits. The variable SOx release predicted by our models both across and among active margins may introduce fO2 heterogeneity to the upper mantle.We thank James Connolly for modelling support and Peter van Keken for providing updated P–T paths for the Syracuse et al. (2010) models. The manuscript benefited from the editorial handling by Helen Williams and from constructive reviews of Maryjo Brounce, Katy Evans, and an anonymous reviewer. JBW acknowledges Fulbright and Chase Distinguished Research fellowships. This work was supported by NSF grant EAR1725301 awarded to AMC

Simple test indicates degree of cure of polyimide coatings

Qualitative test involves immersing a coated cable in methyl-2-pyrrolidone and removing it in one to three minutes. Evidence of any cracking, peeling, or other defects that shows under 20-power magnification indicates that the coating has not been completely cured

Transitional justice and economic policy

The field of transitional justice has faced several challenges in its relatively short life span. The latest of these challenges is the claim for broadening its scope to incorporate social justice- and development-related matters. And in just a few years, the possibility and adequacy of thicker or more holistic conceptions of transitional justice have become mainstream. Nonetheless, since their beginnings these new approaches have been subject to criticism from both within and outside the field. This article describes the trajectory of the scholarly debate on expanding transitional justice to encompass socioeconomic concerns, as well as its main limitations. It starts by exploring the main reasons that led to the historical marginalization of socioeconomic concerns in transitional justice theory and practice. It then considers the rationale for the implementation of broader approaches to transitional justice and closes with a discussion of the main challenges and limitations these proposals face. © 2018 by Annual Reviews. All rights reserved

Quasinodal lines in rhombohedral magnetic materials

A well-established result in condensed matter physics states that materials crystallizing in symmetry groups containing glide reflection symmetries possess nodal lines on the energy bands. These nodal lines are topologically protected and appear on the fixed planes of the reflection in reciprocal space. In the presence of inversion symmetry, the energy bands are degenerate and the band crossings on the fixed plane may be one-dimensional, or may intersect in points, including the case of empty intersection. In the latter case, the crossing is partially or totally avoided, thus producing lines on reciprocal space where the energy gap may be small, and in the former, the nodal lines will endure, thus producing Dirac or double nodal lines. In addition, if the material crystallizes in a ferromagnetic phase where the glide reflection symmetry is broken, the nodal lines hybridize, thus defining lines in reciprocal space where the energy gap may be small. In this work, we concentrate our efforts on the study of nodal lines that hybridize due to magnetization; we have coined the term of quasinodal lines for those lines in reciprocal space where the energy gap is small (less than what can be detected experimentally ∼25 meV). We study magnetic trifluorides and trioxides which crystallize in magnetic space groups 167.107 and 161.71 and we show the existence of quasinodal lines on these materials. We furthermore show that whenever the quasinodal lines are located around the Fermi level then interesting charge and spin transport effects are induced and can be used to detect experimentally these lines. Of particular interest are the half-metallic ferromagnetic phases of PdF3 and LiCuF3 where the large signal of the anomalous Hall conductance is due to the presence of the quasinodal lines on the Fermi level

Topological electronic structure and Weyl points in nonsymmorphic hexagonal materials

Using topological band theory analysis we show that the nonsymmorphic symmetry operations in hexagonal lattices enforce Weyl points at the screw-invariant high-symmetry lines of the band structure. The corepresentation theory and connectivity group theory show that Weyl points are generated by band crossings in accordion-like and hourglass-like dispersion relations. These Weyl points are stable against weak perturbations and are protected by the screw rotation symmetry. Based on first-principles calculations we found a complete agreement between the topological predicted energy dispersion relations and real hexagonal materials. Topological charge (chirality) and Berry curvature calculations show the simultaneous formation of Weyl points and nodal-lines in 4d transition-metal trifluorides such as AgF3 and AuF3. Furthermore, a large intrinsic spin-Hall conductivity was found due to the combined strong spin-orbit coupling and multiple Weyl-point crossings in the electronic structure. These materials could be used to the spin/charge conversion in more energy-efficient spintronic devices