•The garnet megacrysts of Gore Mountain contain former melt inclusions.•Quartz and feldspar polymorphs commonly found as crystallization products of the trapped melt.•Melt production at ultrahigh ...temperature conditions (≥940°C) as result of H2O-present melting of a lower crustal gabbro.•First instance of TTG embryos found in their mafic source rock.•Their mismatched signature suggests that trace elements may not be diagnostic of depth of melting and geodynamic setting.
The garnet megacrysts of Gore Mountain (Adirondacks, US) are world-renown crystals due to their size, up to 1 m in historical record, which makes them the largest known garnets on the planet. We show here that they are also host to the first primary inclusions of trondhjemitic melt found in natural mafic rocks. The petrological and experimental investigation of the inclusions, coupled with phase equilibrium modelling, shows that this melt is the result of H2O-fluxed partial melting at T>900°C of a lower crustal gabbro. The compositional similarity between the trondhjemitic melt inclusions and tonalitic–trondhjemitic–granodioritic (TTGs) melts makes these inclusions a direct natural evidence that melting of mafic rocks generates TTG-like melts, and provides us with the possibility to clarify processes responsible for the formation of the early continental crust. These TTG embryos represent the trondhjemitic end-member of the melts whose emplacement at upper crustal levels, after being modified by mixing and crystallization-related processes, leads to the formation of the TTG terranes. Moreover, our study shows how the melt from H2O-fluxed melting of mafic lower crust has mismatched major and trace element signatures, previously interpreted as evidence of melting at very different pressures. This poses serious limitations to the established use of some chemical features to identify the geodynamic settings (e.g. subduction versus thickened crust) responsible for TTGs generation and the growth of early crust.
Optimism bias or an inconvenient truth? Mortensen, Neil
Bulletin of the Royal College of Surgeons of England,
03/2022, Letnik:
104, Številka:
2
Journal Article
Odprti dostop
Our President reflects on our response to COVID-19 and looks forward to the future of surgical training.
High‐power, durable composite fuel cell membranes are fabricated here by direct membrane deposition (DMD). Poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVDF‐HFP) nanofibers, decorated with CeO2 ...nanoparticles are directly electrospun onto gas diffusion electrodes. The nanofiber mesh is impregnated by inkjet‐printed Nafion ionomer dispersion. This results in 12 µm thin multicomponent composite membranes. The nanofibers provide membrane reinforcement, whereas the attached CeO2 nanoparticles promote improved chemical membrane durability due to their radical scavenging properties. In a 100 h accelerated stress test under hot and dry conditions, the reinforced DMD fuel cell shows a more than three times lower voltage decay rate (0.39 mV h−1) compared to a comparably thin Gore membrane (1.36 mV h−1). The maximum power density of the DMD fuel cell drops by 9%, compared to 54% measured for the reference. Impedance spectroscopy reveals that ionic and mass transport resistance of the DMD fuel cell are unaffected by the accelerated stress test. This is in contrast to the reference, where a 90% increase of the mass transport resistance is measured. Energy dispersive X‐ray spectroscopy reveals that no significant migration of cerium into the catalyst layers occurs during degradation. This proves that the PVDF‐HFP backbone provides strong anchoring of CeO2 in the membrane.
An electrospun PVDF‐HFP nanofiber mesh, decorated with CeO2 nanoparticles, is impregnated by Nafion ionomer dispersion. This results in 12 µm thin composite membranes. A more than three times lower membrane degradation is found compared to a commercial reference. Energy dispersive X‐ray spectroscopy reveals no significant migration of cerium during degradation. This proves the strong anchoring of CeO2 in the membrane.
Most of the World's germanium (Ge) is mined from Ge-rich lignite, where it is commonly associated with elevated arsenic (As), tungsten (W) and beryllium (Be) contents. Over the past decade, new ...evidence showing that World-class Ge deposits result from the interaction of hydrothermal fluids with organic matter in coal seams has emerged. Yet, the chemical state of Ge and associated metals in lignite remains poorly understood. We used Mega-pixel Synchrotron X-ray Fluorescence (MSXRF), X-ray Absorption Near Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) to characterize the oxidation states and chemical bonding environment of Ge, As, and W in two world-class Mesozoic Ge-in-lignite deposits (Lincang, Yunnan, southwestern China; Wulantuga, Inner Mongolia, northeastern China); in lignite-bearing uranium (U) ores from the Beverley deposit (South Australia) hosted in Eocene sandstones; and in lignite and preserved wood in late Oligocene-Miocene fluviatile sediments (Gore, Southland, New Zealand). The aim was to improve our understanding of the enrichment mechanism of Ge in lignite and better evaluate the environmental mobility of Ge and some of the associated metals (specifically As and W) in lignite ores.
In all samples, chemical maps show that Ge is distributed homogeneously (down to 2μm) within the organic matter. XANES and EXAFS data show that Ge exists in the tetravalent oxidation state and in a distorted octahedral coordination with O, consistent with complexing of Ge by organic ligands. In some pyrite-bearing samples, a minor fraction of Ge is also present as Ge(IV) in association with pyrite. In contrast, As displays a more complex speciation pattern, sometimes even in a single sample, including As(III), As(V), and As(−I/+II) in solid solution in sulfides. Arsenic in sulfides occurs in anionic and cationic forms, i.e., it shows both the common substitution for S22− and the substitution for Fe recently discovered in some hydrothermal pyrites. Tungsten was present as W(VI) in distorted octahedral (3+3) coordination. The EXAFS data confirm the absence or minor contribution of individual W-rich minerals such as scheelite or ferberite to W mass balance in the studied samples.
These data show that Ge, W, and probably some As are scavenged via formation of insoluble, oxygen-bridged metal organic complexes in lignite. Destruction of the organic ligands responsible for fixing Ge and W (As) in these lignites is required for liberating the metals, e.g. from waste materials. Geochemical modelling suggests that Ge, W, Be and As all can be extracted from granitic rocks by dilute, low temperature hydrothermal fluids. Germanium is transported mainly as the tetrahedral Ge(OH)4(aq) complex, but fixed as an octahedral oxy-bridged organic complex. The same situation is valid for W, which is transported at the tetrahedral tungstate ion, but most likely scavenged via formation of a 6-coordinated metal-organic species. The Ge-Be-W±As association in Ge-rich coals reflects the source of the metals as well as related scavenging mechanisms.
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This work describes the development of a disposable and wearable screen-printed electrochemical sensor for the determination of chloride ions. The sensor includes three screen-printed ...electrodes: a working, an auxiliary (both carbon paste electrodes), and an Ag/AgCl pseudo-reference electrode. The sensor works by measuring the Nernstian shift of the voltammetric peak potential of ferrocenemethanol in the presence of chloride ions, due to the use of a pseudo-reference electrode in the electrodic system. The measurements are easily taken by dropping the sample onto the electrodic surface.
Different flexible materials, including textiles, were studied as substrates of the electrodic system. A study of ink adherence and conductivity in these materials was carried out. The use of Gore-Tex® displayed good ink adherence, acceptable conductivity and waterproof properties. These features make it an excellent support for wearable sensors.
The reproducibility and repeatability, in terms of relative standard deviation values of the developed Gore-Tex sensor, were below 3% (n=5) and the detection limit was 0.2mM (α=β=0.05).
The sensor was successfully applied to determine the chloride content in sea water.
The Supreme Court's intervention in the 2000 election will shape American law and democracy long after George W. Bush has left the White House. This vitally important book brings together a broad ...range of preeminent legal scholars who address the larger questions raised by the Supreme Court's actions. Did the Court's decision violate the rule of law? Did it inaugurate an era of super-politicized jurisprudence? How should Bush v. Gore change the terms of debate over the next round of Supreme Court appointments?The contributors-Bruce Ackerman, Jack Balkin, Guido Calabresi, Steven Calabresi, Owen Fiss, Charles Fried, Robert Post, Margaret Jane Radin, Jeffrey Rosen, Jed Rubenfeld, Cass Sunstein, Laurence Tribe, and Mark Tushnet-represent a broad political spectrum. Their reactions to the case are varied and surprising, filled with sparkling argument and spirited debate. This is a must-read book for thoughtful Americans everywhere.
Background and aim: The GORE® CARDIOFORM (GCO) septal occluder is an atrial septal defect/patent foramen ovale closure device with theoretical advantages over other commercialized devices thanks to ...its softness and anatomical compliance. Our aim was to evaluate the short- and medium-term electrocardiographic changes after percutaneous ASD closure with GCO in a pediatric population. Methods: We enrolled 39 patients with isolated ASD submitted to trans-catheter closure from January 2020 to June 2021. ECG was performed before, at 24 h and 6 months after the procedure. P wave dispersion, QTc and QTc dispersion were calculated. ECG Holter was recorded at 6 months after implantation. Results: Patients’ age and body surface area (BSA) were 8.2 ± 4.2 years and 1.0 ± 0.3 m2 respectively. At the baseline, mean P wave dispersion was 40 ± 15 msec and decreased at 24 h (p < 0.002), without any further change at 6 months. At 24 h, PR conduction and QTc dispersion significantly improved (p = 0.018 and p < 0.02 respectively), while the absolute QTc value considerably improved after 6 months. During mid-term follow-up, QTc dispersion remained stable without a significant change in PR conduction. The baseline cardiac frequency was 88.6 ± 12.6 bpm, followed by a slight reduction at 24 h, with a further amelioration at 6 months after the procedure (87.3 ± 14.2, p = 0.9 and 81.0 ± 12.7, p = 0.009, respectively). After device deployment, two patients developed transient, self-limited junctional rhythm. One of them needed a short course of Flecainide for atrial ectopic tachycardia. No tachy/brady-arrhythmias were recorded at the 6-month follow-up. ASD closure resulted in a marked decrease in right heart volumes and diameters at 6 months after percutaneous closure. Conclusions: Percutaneous ASD closure with the GCO device results in significant, sudden improvement of intra-atrial, atrio-ventricular and intraventricular electrical homogeneity. This benefit persists unaltered over a medium-term follow-up. These electrical changes are associated with a documented positive right heart volumetric remodeling at mid-term follow-up.
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