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Mantle oxygen fugacity exerts a primary control on mass exchange between Earth's surface and interior at subduction zones, but the major factors controlling mantle oxygen fugacity (such as volatiles and phase assemblages) and how tectonic cycles drive its secular evolution are still debated. We present integrated measurements of redox-sensitive ratios of oxidized iron to total iron (Fe³⁺/ΣFe), determined with Fe K-edge micro-x-ray absorption near-edge structure spectroscopy, and pre-eruptive magmatic H₂O contents of a global sampling of primitive undegassed basaltic glasses and melt inclusions covering a range of plate tectonic settings. Magmatic Fe³⁺/ΣFe ratios increase toward subduction zones (at ridges, 0.13 to 0.17; at back arcs, 0.15 to 0.19; and at arcs, 0.18 to 0.32) and correlate linearly with H₂O content and element tracers of slab-derived fluids. These observations indicate a direct link between mass transfer from the subducted plate and oxidation of the mantle wedge.

The oxidation state of Earth's upper mantle both influences and records mantle evolution, but systematic fine-scale variations in upper mantle oxidation state have not previously been recognized in mantle-derived lavas from mid-ocean ridges. Through a global survey of mid-ocean ridge basalt glasses, we show that mantle oxidation state varies systematically as a function of mantle source composition. Negative correlations between Fe³⁺/ΣFe ratios and indices of mantle enrichment—such as ⁸⁷Sr/⁸⁶Sr, ²⁰⁸Pb/²⁰⁴Pb, Ba/La, and Nb/Zr ratios—reveal that enriched mantle is more reduced than depleted mantle. Because carbon may act to simultaneously reduce iron and generate melts that share geochemical traits with our reduced samples, we propose that carbon creates magmas at ridges that are reduced and enriched.

Oxygen fugacity (fO2) exerts first-order control on the geochemical evolution of planetary interiors, and the Fe3+/ΣFe ratios of silicate glasses provide a useful proxy for fO2. Fe K-edge micro-X-ray absorption near-edge structure (XANES) spectroscopy allows researchers to micro-analytically determine the Fe3+/ΣFe ratios of silicate glasses with high precision. In this study we characterize hydrous and anhydrous basalt glass standards with Mossbauer and XANES spectroscopy and show that synchrotron radiation causes progressive changes to the XANES spectra of hydrous glasses as a function of radiation dose (here defined as total photons delivered per square micrometer), water concentration, and initial Fe3+/ΣFe ratio. We report experiments from eight different radiation dose conditions and show that Fe in hydrous silicate glasses can undergo rapid oxidation upon exposure to radiation. The rate and degree of oxidation correlates with radiation dose and the product of water concentration and ferrous/ferric iron oxide ratio on a molar basis (Φ = XHO0.5·XFeO/XFeO1.5). For example, a basalt glass with 4.9 wt% dissolved H2O and Fe3+/ΣFe = 0.19 from its Mossbauer spectrum may appear to have Fe3+/ΣFe ≥ 0.35 when analyzed over several minutes at a nominal flux density of ∼2 × 109 photons/s/µm2. This radiation-induced increase in Fe3+/ΣFe ratio would lead to overestimation of fO2 by about two orders of magnitude, with dramatic consequences for the interpretation of geological processes. The sample area exposed to radiation shows measureable hydrogen loss, consistent with radiation-induced breaking of O-H bonds, associated H migration and loss, and oxidation of Fe2+. This mechanism is consistent with the observation that anhydrous glasses show no damage under any beam conditions. Cryogenic cooling does not mitigate, but rather accelerates, iron oxidation. The effects of beam damage appear to persist indefinitely. We detect beam damage at the lowest photon flux densities tested (3 × 106 photons/s/µm2); however, at flux densities ≤6 × 107 photons/s/µm2, the hydrous glass calibration curve defined by the centroid (derived from XANES spectra) and Fe3+/ΣFe ratios (derived from Mossbauer spectra) is indistinguishable from the anhydrous calibration curve within the accuracy achievable with Mossbauer spectroscopy. Thus, published Fe3+/ΣFe ratios from hydrous glasses measured at low photon flux densities are likely to be accurate within measurement uncertainty with respect to what would have been measured by Mossbauer spectroscopy. These new results demonstrate that to obtain accurate Fe3+/ΣFe ratios from hydrous, mafic, silicate glasses, it is first necessary to carefully monitor changes in the XANES spectra as a function of incident dose (e.g., fixed-energy scan). Defocusing and attenuating the beam may prevent significant oxidation of Fe in mafic water-bearing glasses.

Recent diving with the JAMSTEC Shinkai 6500 manned submersible in the Mariana fore arc southeast of Guam has discovered that MORB‐like tholeiitic basalts crop out over large areas. These “fore‐arc basalts” (FAB) underlie boninites and overlie diabasic and gabbroic rocks. Potential origins include eruption at a spreading center before subduction began or eruption during near‐trench spreading after subduction began. FAB trace element patterns are similar to those of MORB and most Izu‐Bonin‐Mariana (IBM) back‐arc lavas. However, Ti/V and Yb/V ratios are lower in FAB reflecting a stronger prior depletion of their mantle source compared to the source of basalts from mid‐ocean ridges and back‐arc basins. Some FAB also have higher concentrations of fluid‐soluble elements than do spreading center lavas. Thus, the most likely origin of FAB is that they were the first lavas to erupt when the Pacific Plate began sinking beneath the Philippine Plate at about 51 Ma. The magmas were generated by mantle decompression during near‐trench spreading with little or no mass transfer from the subducting plate. Boninites were generated later when the residual, highly depleted mantle melted at shallow levels after fluxing by a water‐rich fluid derived from the sinking Pacific Plate. This magmatic stratigraphy of FAB overlain by transitional lavas and boninites is similar to that found in many ophiolites, suggesting that ophiolitic assemblages might commonly originate from near‐trench volcanism caused by subduction initiation. Indeed, the widely dispersed Jurassic and Cretaceous Tethyan ophiolites could represent two such significant subduction initiation events.

Patient-centric resident conferences (PCRCs) provide meaningful time to connect with and learn from patients. This qualitative study explores themes of patients’ perioperative experiences from PCRCs through patient and resident perspectives. General Surgery residents participated in six PCRCs, which include condensed standard didactics to accommodate a patient panel regarding their perioperative experience. Panel transcripts and resident survey responses describing what they learned were coded using grounded theory methodology. Themes were evaluated and compared. 76 identified codes were grouped into major categories: “Medical/Surgical Knowledge,” “Patient Perspective,” “Patient-Physician Relationship,” and “Communication.” Themes from resident responses predominantly paralleled patient discussion, with common themes including “impact of disease and surgery on patient” and “compassion/empathy.” “Medical/surgical knowledge” was only present in resident responses while themes regarding quality of life were more frequent in patient transcripts. PCRCs are a valuable tool in resident education to understand patients’ perioperative experiences. Themes from patient panels complement, but do not replace, information covered in didactic lectures. •Patient-centric resident conferences are a valuable tool in resident education.•PCRCs help residents understand patients' perioperative experiences.•Patients value communication, quality of life, and the patient-physician relationship.•Residents do not emphasize the impact of the system on perioperative care.•Themes from PCRCs are complimentary to material covered in resident didactics.

Examination of the global uranium cycle — whereby uranium from the Earth’s crust is first transported to the oceans and then returned, by subduction, to the mantle — shows that the subducted uranium is isotopically distinct from the Earth as a whole and that this signature has been stirred throughout upper mantle, arguably within the past 600 million years. Terrestrial uranium isotope cycle revealed Morten Andersen et al . show that uranium subducted into the mantle should be isotopically distinct, with a high 238 U/ 235 U ratio, as a result of alteration processes at the bottom of an oxic ocean, and mid-ocean-ridge basalts do indeed have a higher 238 U/ 235 U ratio than the bulk Earth, confirming the widespread recycling of uranium in the upper mantle. Whilst it has been argued that many ocean island basalts also contain a recycled component, the authors find that their uranium isotopic compositions are unperturbed from that of the bulk Earth. This suggests that that the subducted uranium in ocean island basalts was isotopically unfractionated prior to full oceanic oxidation at around 600 million years ago, reflecting the greater antiquity of the ocean island basalt source. In contrast, the uranium isotopic composition of mid-ocean-ridge basalts requires convective stirring of recycled uranium throughout the upper mantle within the past 600 million years. Changing conditions on the Earth’s surface can have a remarkable influence on the composition of its overwhelmingly more massive interior. The global distribution of uranium is a notable example. In early Earth history, the continental crust was enriched in uranium. Yet after the initial rise in atmospheric oxygen, about 2.4 billion years ago, the aqueous mobility of oxidized uranium resulted in its significant transport to the oceans and, ultimately, by means of subduction, back to the mantle 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 . Here we explore the isotopic characteristics of this global uranium cycle. We show that the subducted flux of uranium is isotopically distinct, with high 238 U/ 235 U ratios, as a result of alteration processes at the bottom of an oxic ocean. We also find that mid-ocean-ridge basalts (MORBs) have 238 U/ 235 U ratios higher than does the bulk Earth, confirming the widespread pollution of the upper mantle with this recycled uranium. Although many ocean island basalts (OIBs) are argued to contain a recycled component 9 , their uranium isotopic compositions do not differ from those of the bulk Earth. Because subducted uranium was probably isotopically unfractionated before full oceanic oxidation, about 600 million years ago, this observation reflects the greater antiquity of OIB sources. Elemental and isotope systematics of uranium in OIBs are strikingly consistent with previous OIB lead model ages 10 , indicating that these mantle reservoirs formed between 2.4 and 1.8 billion years ago. In contrast, the uranium isotopic composition of MORB requires the convective stirring of recycled uranium throughout the upper mantle within the past 600 million years.

Objective. To determine the impact of the holistic redesign of top 200 medications learning activities within a Doctor of Pharmacy (PharmD) curriculum by comparing student performances on a comprehensive examination before and after the redesign. Methods. During a curricular revision at The Ohio State University College of Pharmacy that began with the class of 2020, learning activities involving the top 200 medications were implemented that involved repeated retrieval and mastery concepts, alignment with therapeutic coursework, and autonomous learning regarding the top 200 medications. A high-stakes comprehensive top 200 medications examination was administered to students at the end of their third professional year both before and after implementation of these activities. The difference in the percentage of students who achieved a satisfactory score on the comprehensive examination was compared between cohorts prior to and following the curricular redesign. Results. The study analyzed results from 134, 130, and 120 students from three PharmD classes (one before and two after the redesign of top 200 medications activities). Following the redesign, a higher percentage of students achieved a satisfactory score of 85% on the examination (class of 2020: 116/130, 89.2%; class of 2022: 107/120, 89.2%) compared to before the redesign (class of 2019: 88/134, 65.7%). Conclusion. The combination of repeated retrieval and mastery, alignment with therapeutic coursework, and development of autonomous learning can significantly increase student knowledge and retention of top 200 medications.

A major goal of E/V Nautilus expeditions is to explore the ocean in order to provide a rich foundation of publicly accessible data to stimulate follow-on exploration, research, and management activities. To this end, the Ocean Exploration Trust has been partnering with the Museum of Comparative Zoology at Harvard University and the Marine Geological Samples Laboratory at the University of Rhode Island to permanently curate biological and geological samples, respectively, that are collected on Nautilus expeditions, as well as to make these samples available to qualified researchers around the world. The Marine Geological Samples Laboratory (MGSL) is an open-access sample repository funded by NSF that houses 15,000+ samples of dredged rocks, marine sediment cores, and ROV-collected materials from global ocean basins. In 2022, the MGSL accessioned 221 grab samples and push cores collected by ROV Hercules. Sample ingestion typically involves cutting rock samples open to facilitate accurate descriptions of their internal characteristics.

BackgroundTotal mesorectal excision (TME) is the gold standard for oncologic resection in low and mid rectal cancers. However, abdominal approaches to TME can be hampered by poor visibility, inadequate retraction, and distal margin delineation. Transanal TME (taTME) is a promising hybrid technique that was developed to mitigate the difficulties of operating in the low pelvis and to optimize the circumferential resection and distal margins.MethodsThe objective of this study was to characterize our experience implementing taTME at our institution in a technically challenging patient population. We performed a retrospective review of consecutive patients who underwent taTMEs between November 2013 and May 2019 for rectal cancer at a tertiary community cancer center. Outcome measures included pathologic grading of TME specimen, post-operative complications, and oncologic outcomes.ResultsForty-four patients with mid and low rectal cancer underwent low anterior resection via taTME. The most common staging modality was rectal MRI which demonstrated T3 or T4 tumors in 89% of our patients prior to neoadjuvant. Eighty-six percent of patients underwent neoadjuvant chemoradiation. The initial cases were performed sequentially as a single team, but we later transitioned to a synchronous, two-team approach. Ninety-one percent of TME grades were complete or near complete. Only one patient (2.3%) had a positive circumferential margin. Six patients developed anastomotic leaks with an overall anastomotic complication rate of 18.2%. Two patients (4.5%) with primary rectal cancer developed local recurrence, one of which developed multifocal local recurrence.ConclusionsUsing the taTME approach on selected locally advanced low rectal cancers, especially in technically complex irradiated and obese male patients, has yielded comparably safe and effective outcomes to laparoscopic proctectomy.

Mid-ocean ridge volcanoes sample a mantle that varies in temperature and composition. [Also see Report by Dalton et al. ] The global mid-ocean ridge system is an interconnected network of volcanoes that produces the oceanic crust, which covers 70% of Earth's surface. The physical and chemical attributes of mid-ocean ridges, such as the depth of the volcanic ridge axis below the sea surface, the thickness of the oceanic crust created there, the composition of the erupted lava, and the way seismic waves interact with the mantle beneath the ridge, collectively reflect the properties of the mantle that melts to form the oceanic crust. On page 80 of this issue, Dalton et al. ( 1 ) explore relationships between global seismic wave velocities in the mantle beneath mid-ocean ridges and a global data set of ridge depth and lava chemistry ( 2 ). They find strong correlations between these three factors, ultimately linking the trends to a global mantle temperature variation of ∼250°C.