Diagenetic incorporation of Sr into aragonitic bivalve shells: implications for chronostratigraphic and palaeoenvironmental interpretations

Aragonite is easily altered during diagenesis, therefore presumed pristine when present. In effect, beyond polymorphic transformation to calcite, alteration paths of aragonite remain poorly understood despite heavy reliance on such material to produce palaeoenvironmental and chronostratigraphic interpretations. Previous work on core material from Southern McMurdo Sound, Antarctica, showed that unlike their calcitic counterparts, seemingly unaltered aragonite shell fragments invariably produced older than expected 87Sr/86Sr ages. In this study, we pursued additional analyses of these aragonite shells and of the porewater of the core to understand this discrepancy. Aragonite mineralogy was reconfirmed and elemental mapping of shell fragments revealed growth lines within the middle layer suggestive of good preservation. The outer layer, however, showed anomalously high Sr concentrations (average 4·5 ± 0·6 mole% SrCO3; ca 25 mmol mol−1 Sr/Ca) and was depleted in 18O and 13C compared to the middle layer, both features inconsistent with pristine material. The δ18O values and Sr concentrations of the porewater were used to model outer layer compositions reasonably well. Coincidentally, porewater Sr isotope composition was in general agreement with the age model of the core only at the aragonite‐bearing interval suggesting that Sr‐isotopic disequilibrium between porewater and the carbonates was the rule rather than the exception in the core. The Sr isotope compositions of the aragonite shells are most likely the result of early diagenesis as suggested by the inconsistent O and C isotope compositions between shell layers and the anomalously high Sr concentrations. We conclude that knowledge of Sr concentration and distribution in shells is critical to determine the viability of Sr stratigraphy and the scale at which it may be applied. Reliance on traditional indicators of lack of alteration, such as cathodoluminescence, Mn‐Fe concentration, and the presence of labile mineralogies to assert chronostratigraphic and palaeoenvironmental questions may produce erroneous conclusions due to obscurely altered material.Compositional map of Sr over BSE image and representative SEM detail overlay from a Miocene aragonitic Retrotape andrillorum bivalve, Southern McMurdo Sound, Antarctica. Signs of apparent good preservation, such as the presence of growth bands and the preservation of crystalline structure and mineralogy, appear in contrast to anomalously high Sr concentrations. Results suggest that relying solely on traditional methods to rule out diagenesis may in some cases lead to erroneous conclusions due to obscure alteration patterns.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/113152/1/dep23.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/113152/2/dep23-sup-0003-AppendixS3.pd

Systematic meta-review of supported self-management for asthma: a healthcare perspective

BACKGROUND: Supported self-management has been recommended by asthma guidelines for three decades; improving current suboptimal implementation will require commitment from professionals, patients and healthcare organisations. The Practical Systematic Review of Self-Management Support (PRISMS) meta-review and Reducing Care Utilisation through Self-management Interventions (RECURSIVE) health economic review were commissioned to provide a systematic overview of supported self-management to inform implementation. We sought to investigate if supported asthma self-management reduces use of healthcare resources and improves asthma control; for which target groups it works; and which components and contextual factors contribute to effectiveness. Finally, we investigated the costs to healthcare services of providing supported self-management. METHODS: We undertook a meta-review (systematic overview) of systematic reviews updated with randomised controlled trials (RCTs) published since the review search dates, and health economic meta-analysis of RCTs. Twelve electronic databases were searched in 2012 (updated in 2015; pre-publication update January 2017) for systematic reviews reporting RCTs (and update RCTs) evaluating supported asthma self-management. We assessed the quality of included studies and undertook a meta-analysis and narrative synthesis. RESULTS: A total of 27 systematic reviews (n = 244 RCTs) and 13 update RCTs revealed that supported self-management can reduce hospitalisations, accident and emergency attendances and unscheduled consultations, and improve markers of control and quality of life for people with asthma across a range of cultural, demographic and healthcare settings. Core components are patient education, provision of an action plan and regular professional review. Self-management is most effective when delivered in the context of proactive long-term condition management. The total cost (n = 24 RCTs) of providing self-management support is offset by a reduction in hospitalisations and accident and emergency visits (standard mean difference 0.13, 95% confidence interval -0.09 to 0.34). CONCLUSIONS: Evidence from a total of 270 RCTs confirms that supported self-management for asthma can reduce unscheduled care and improve asthma control, can be delivered effectively for diverse demographic and cultural groups, is applicable in a broad range of clinical settings, and does not significantly increase total healthcare costs. Informed by this comprehensive synthesis of the literature, clinicians, patient-interest groups, policy-makers and providers of healthcare services should prioritise provision of supported self-management for people with asthma as a core component of routine care. SYSTEMATIC REVIEW REGISTRATION: RECURSIVE: PROSPERO CRD42012002694 ; PRISMS: PROSPERO does not register meta-reviews

Report from Working Group 3: Beyond the standard model physics at the HL-LHC and HE-LHC

This is the third out of five chapters of the final report [1] of the Workshop on Physics at HL-LHC, and perspectives on HE-LHC [2]. It is devoted to the study of the potential, in the search for Beyond the Standard Model (BSM) physics, of the High Luminosity (HL) phase of the LHC, defined as $3$ ab$^{-1}$ of data taken at a centre-of-mass energy of 14 TeV, and of a possible future upgrade, the High Energy (HE) LHC, defined as $15$ ab$^{-1}$ of data at a centre-of-mass energy of 27 TeV. We consider a large variety of new physics models, both in a simplified model fashion and in a more model-dependent one. A long list of contributions from the theory and experimental (ATLAS, CMS, LHCb) communities have been collected and merged together to give a complete, wide, and consistent view of future prospects for BSM physics at the considered colliders. On top of the usual standard candles, such as supersymmetric simplified models and resonances, considered for the evaluation of future collider potentials, this report contains results on dark matter and dark sectors, long lived particles, leptoquarks, sterile neutrinos, axion-like particles, heavy scalars, vector-like quarks, and more. Particular attention is placed, especially in the study of the HL-LHC prospects, to the detector upgrades, the assessment of the future systematic uncertainties, and new experimental techniques. The general conclusion is that the HL-LHC, on top of allowing to extend the present LHC mass and coupling reach by $20-50\%$ on most new physics scenarios, will also be able to constrain, and potentially discover, new physics that is presently unconstrained. Moreover, compared to the HL-LHC, the reach in most observables will, generally more than double at the HE-LHC, which may represent a good candidate future facility for a final test of TeV-scale new physics

Diagenetic incorporation of Sr into aragonitic bivalve shells: implications for chronostratigraphic and palaeoenvironmental interpretations

Aragonite is easily altered during diagenesis, therefore presumed pristine when present. In effect, beyond polymorphic transformation to calcite, alteration paths of aragonite remain poorly understood despite heavy reliance on such material to produce palaeoenvironmental and chronostratigraphic interpretations. Previous work on core material from Southern McMurdo Sound, Antarctica, showed that unlike their calcitic counterparts, seemingly unaltered aragonite shell fragments invariably produced older than expected 87Sr/86Sr ages. In this study, we pursued additional analyses of these aragonite shells and of the porewater of the core to understand this discrepancy. Aragonite mineralogy was reconfirmed and elemental mapping of shell fragments revealed growth lines within the middle layer suggestive of good preservation. The outer layer, however, showed anomalously high Sr concentrations (average 4.5 ± 0.6 mole% SrCO3; ca 25 mmol mol-1 Sr/Ca) and was depleted in 18O and 13C compared to the middle layer, both features inconsistent with pristine material. The δ18O values and Sr concentrations of the porewater were used to model outer layer compositions reasonably well. Coincidentally, porewater Sr isotope composition was in general agreement with the age model of the core only at the aragonite-bearing interval suggesting that Sr-isotopic disequilibrium between porewater and the carbonates was the rule rather than the exception in the core. The Sr isotope compositions of the aragonite shells are most likely the result of early diagenesis as suggested by the inconsistent O and C isotope compositions between shell layers and the anomalously high Sr concentrations. We conclude that knowledge of Sr concentration and distribution in shells is critical to determine the viability of Sr stratigraphy and the scale at which it may be applied. Reliance on traditional indicators of lack of alteration, such as cathodoluminescence, Mn-Fe concentration, and the presence of labile mineralogies to assert chronostratigraphic and palaeoenvironmental questions may produce erroneous conclusions due to obscurely altered material

Electrochemical, Spectroscopic, and Computational Investigations on Redox Reactions of Selenium Species on Galena Surfaces

Despite previous studies investigating selenium (Se) redox reactions in the presence of semiconducting minerals, Se redox reactions mediated by galena (PbS) are poorly understood. In this study, the redox chemistry of Se on galena is investigated over a range of environmentally relevant Eh and pH conditions (+0.3 to −0.6 V vs. standard hydrogen electrode, SHE; pH 4.6) using a combination of electrochemical, spectroscopic, and computational approaches. Cyclic voltammetry (CV) measurements reveal one anodic/cathodic peak pair at a midpoint potential of +30 mV (vs. SHE) that represents reduction and oxidation between HSeO3− and H2Se/HSe−. Two peak pairs with midpoint potentials of −400 and −520 mV represent the redox transformation from Se(0) to HSe− and H2Se species, respectively. The changes in Gibbs free energies of adsorption of Se species on galena surfaces as a function of Se oxidation state were modeled using quantum-mechanical calculations and the resulting electrochemical peak shifts are (−0.17 eV for HSeO3−/H2Se, −0.07 eV for HSeO3−/HSe−, 0.15 eV for Se(0)/HSe−, and −0.15 eV for Se(0)/H2Se). These shifts explain deviation between Nernstian equilibrium redox potentials and observed midpoint potentials. X-ray photoelectron spectroscopy (XPS) analysis reveals the formation of Se(0) potentials below −100 mV and Se(0) and Se(−II) species at potentials below −400 mV

Understanding Calcite Wettability Alteration through Surface Potential Measurements and Molecular Simulations

Mineral wettability and wettability alteration are important factors that determine the distribution and mobility of oil during the recovery process. Because wettability is dependent on many factors (e.g., hydrocarbon composition, mineralogy, and pH), predicting mineral wettability is often difficult. The goal of this study is to look at changes that occur on the mineral itself, specifically changes in the surface structure and surface potential, using experimental methods complemented by quantum-mechanical calculations to better understand the molecular-level processes involved in wettability alteration. Nanoscale surface imaging is combined with Kelvin probe force microscopy (KPFM) to characterize changes in topography and surface potential for water-wet (hydrophilic) and oil-wet (hydrophobic) calcite surfaces, using the surfactant hexamethyl­disilazane (NHSi₂(CH₃)₆, HMDS) to render the calcite surface oil-wet. KPFM measurements show that HMDS adsorbs preferentially on step edges of the calcite surface and is coupled by an increase in surface potential, which suggests a decrease in electron density in the valence band wherever HMDS is adsorbed. Density functional theory (DFT) calculations of HMDS adsorption on calcite confirm an increase in the surface potential of oil-wet calcite and show that Ca corner sites are associated with the most favorable HMDS adsorption energies. Coadsorption of H⁺ and OH^– with HMDS is more likely to occur at edges and Ca kink sites and indicates that this surfactant may be an effective wettability modifier at a range of pH conditions. This study is the first application of KPFM to mineral wettability and demonstrates that with further development KPFM can be a powerful tool to study interactions between specific functional groups and surface sites modifying the surface’s electronic structure and wettability