Linking Redox Processes and Black Shale Resource Potential

Black shales, such as the Mississippian (~330 Ma) Bowland Shale Formation, are targets for unconventional hydrocarbon exploration in the UK and in equivalents across Europe. Despite this interest, global decarbonisation, by definition, will either require; (1) complete replacement of natural gas with renewables and nuclear power generation, or; (2) moderate to limited natural gas use globally or locally, for example as a ‘bridge fuel’, as a source for hydrogen via steam reformation, or coupled to carbon capture and storage (CCS) technology. Any of these scenarios will increase the demand for transition metals such as V, Co and Ni, key elements used for energy storage and as catalysts in steam reformation. Black shales in general can host ore-grade enrichments in these metals, although the exact resource potential of UK Mississippian black shales remains unresolved. We integrate comprehensive sedimentological and geochemical data from three sections through the Bowland Shale in the Craven Basin (Lancashire, UK) to explore the links between controls on hydrocarbon and metal prospectivity. The Bowland Shale at these sites is a highly heterogeneous and complex ~120 m thick succession comprising carbonate-rich, siliceous and siliciclastic, argillaceous mudstones. These sedimentary facies developed in response to a combination of high-frequency (~111 kyr) sea level changes, fault activity at the basin margins and linkage with the nearby prograding Pendle delta system. Palaeoredox proxies such as Fe-speciation, redox-sensitive trace elements and S isotope analysis from extracted pyrite (δ34Spy) demonstrate intervals associated with metal enrichment were deposited under anoxic and at least intermittently euxinic (sulphidic) bottom water conditions. Trace element enrichment ‘V scores’ (sum of V+Mo+Se+Ni+Zn in ppm) indicate the greatest enrichments in these key transition metals and non-metals are associated with deposition under strongly sulphidic conditions during marine transgressions. V scores in these intervals are often >400 ppm and sometimes >1000 ppm. These bulk enrichments are comparable to stratiform low-grade ores such as the Upper Mudstone Member of the Devonian Popovich Formation (Nevada, USA). Hosts for these metals likely include solid sulphides such as pyrite, organic matter and possibly phosphates or carbonates. Critically, a process of switching between ferruginous and euxinic conditions in anoxic porewaters, termed ‘redox oscillation’, is recognised by a distinctive redox-sensitive trace element enrichment pattern, particularly competition between V and Ni metalation. Redox oscillation operated during periods of reduced sea level, where an increased supply of reactive Fe to the basin promoted development of intermittently ferruginous conditions in bottom waters and early diagenetic porewaters. Therefore the distribution of many redox-sensitive elements through the Bowland Shale is predictable. If these elements can be efficiently extracted from the mineral or organic hosts, UK Mississippian black shales may represent a significant resource. This work also improves understanding of the potential for co-extraction of metals during hydraulic fracturing, or during remediation of waste water. Future work will seek to understand which minerals or organic compounds host these redox-sensitive trace elements

Adjunctive rifampicin for Staphylococcus aureus bacteraemia (ARREST): a multicentre, randomised, double-blind, placebo-controlled trial.

BACKGROUND: Staphylococcus aureus bacteraemia is a common cause of severe community-acquired and hospital-acquired infection worldwide. We tested the hypothesis that adjunctive rifampicin would reduce bacteriologically confirmed treatment failure or disease recurrence, or death, by enhancing early S aureus killing, sterilising infected foci and blood faster, and reducing risks of dissemination and metastatic infection. METHODS: In this multicentre, randomised, double-blind, placebo-controlled trial, adults (≥18 years) with S aureus bacteraemia who had received ≤96 h of active antibiotic therapy were recruited from 29 UK hospitals. Patients were randomly assigned (1:1) via a computer-generated sequential randomisation list to receive 2 weeks of adjunctive rifampicin (600 mg or 900 mg per day according to weight, oral or intravenous) versus identical placebo, together with standard antibiotic therapy. Randomisation was stratified by centre. Patients, investigators, and those caring for the patients were masked to group allocation. The primary outcome was time to bacteriologically confirmed treatment failure or disease recurrence, or death (all-cause), from randomisation to 12 weeks, adjudicated by an independent review committee masked to the treatment. Analysis was intention to treat. This trial was registered, number ISRCTN37666216, and is closed to new participants. FINDINGS: Between Dec 10, 2012, and Oct 25, 2016, 758 eligible participants were randomly assigned: 370 to rifampicin and 388 to placebo. 485 (64%) participants had community-acquired S aureus infections, and 132 (17%) had nosocomial S aureus infections. 47 (6%) had meticillin-resistant infections. 301 (40%) participants had an initial deep infection focus. Standard antibiotics were given for 29 (IQR 18-45) days; 619 (82%) participants received flucloxacillin. By week 12, 62 (17%) of participants who received rifampicin versus 71 (18%) who received placebo experienced treatment failure or disease recurrence, or died (absolute risk difference -1·4%, 95% CI -7·0 to 4·3; hazard ratio 0·96, 0·68-1·35, p=0·81). From randomisation to 12 weeks, no evidence of differences in serious (p=0·17) or grade 3-4 (p=0·36) adverse events were observed; however, 63 (17%) participants in the rifampicin group versus 39 (10%) in the placebo group had antibiotic or trial drug-modifying adverse events (p=0·004), and 24 (6%) versus six (2%) had drug interactions (p=0·0005). INTERPRETATION: Adjunctive rifampicin provided no overall benefit over standard antibiotic therapy in adults with S aureus bacteraemia. FUNDING: UK National Institute for Health Research Health Technology Assessment

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements