Value of minimum intensity projections for chest CT in COVID-19 patients

Purpose: To investigate whether minimum intensity projection (MinIP) reconstructions enable more accurate depiction of pulmonary ground-glass opacity (GGO) compared to standard transverse sections and multiplanar reformat (MPR) series in patients with suspected coronavirus disease 2019 (COVID-19). Method: In this multinational study, chest CT scans of 185 patients were retrospectively analyzed. Diagnostic accuracy, diagnostic confidence, image quality regarding the assessment of GGO, as well as subjective time-efficiency of MinIP and standard MPR series were analyzed based on the assessment of six radiologists. In addition, the suitability for COVID-19 evaluation, image quality regarding GGO and subjective time-efficiency in clinical routine was assessed by five clinicians. Results: The reference standard revealed a total of 149 CT scans with pulmonary GGO. MinIP reconstructions yielded significantly higher sensitivity (99.9 % vs 95.6 %), specificity (95.8 % vs 86.1 %) and accuracy (99.1 % vs 93.8 %) for assessing of GGO compared with standard MPR series. MinIP reconstructions achieved significantly higher ratings by radiologists concerning diagnostic confidence (medians, 5.00 vs 4.00), image quality (medians, 4.00 vs 4.00), contrast between GGO and unaffected lung parenchyma (medians, 5.00 vs 4.00) as well as subjective time-efficiency (medians, 5.00 vs 4.00) compared with MPR-series (all P <.001). Clinicians preferred MinIP reconstructions for COVID-19 assessment (medians, 5.00 vs 3.00), image quality regarding GGO (medians, 5.00 vs 3.00) and subjective time-efficiency in clinical routine (medians, 5.00 vs 3.00). Conclusions: MinIP reconstructions improve the assessment of COVID-19 in chest CT compared to standard images and may be suitable for routine application

Methane Clumped Isotopes: Progress and Potential for a New Isotopic Tracer

The isotopic composition of methane is of longstanding geochemical interest, with important implications for understanding petroleum systems, atmospheric greenhouse gas concentrations, the global carbon cycle, and life in extreme environments. Recent analytical developments focusing on multiply substituted isotopologues (‘clumped isotopes’) are opening a valuable new window into methane geochemistry. When methane forms in internal isotopic equilibrium, clumped isotopes can provide a direct record of formation temperature, making this property particularly valuable for identifying different methane origins. However, it has also become clear that in certain settings methane clumped isotope measurements record kinetic rather than equilibrium isotope effects. Here we present a substantially expanded dataset of methane clumped isotope analyses, and provide a synthesis of the current interpretive framework for this parameter. In general, clumped isotope measurements indicate plausible formation temperatures for abiotic, thermogenic, and microbial methane in many geological environments, which is encouraging for the further development of this measurement as a geothermometer, and as a tracer for the source of natural gas reservoirs and emissions. We also highlight, however, instances where clumped isotope derived temperatures are higher than expected, and discuss possible factors that could distort equilibrium formation temperature signals. In microbial methane from freshwater ecosystems, in particular, clumped isotope values appear to be controlled by kinetic effects, and may ultimately be useful to study methanogen metabolism

Creating and curating an archive: Bury St Edmunds and its Anglo-Saxon past

This contribution explores the mechanisms by which the Benedictine foundation of Bury St Edmunds sought to legitimise and preserve their spurious pre-Conquest privileges and holdings throughout the Middle Ages. The archive is extraordinary in terms of the large number of surviving registers and cartularies which contain copies of Anglo-Saxon charters, many of which are wholly or partly in Old English. The essay charts the changing use to which these ancient documents were put in response to threats to the foundation's continued enjoyment of its liberties. The focus throughout the essay is to demonstrate how pragmatic considerations at every stage affects the development of the archive and the ways in which these linguistically challenging texts were presented, re-presented, and represented during the Abbey’s history

(Table 1) Isotopes on interstitial gases at DSDP Leg 64 Holes

The origin of the interstitial gases of Hole 479 is bacterial. This is indicated by a positive correlation of the 13C concentration in interstitial methane and CO2 in the shallower depths of the hole. Below a depth of 100 meters, the interstitial CO2 becomes increasingly depleted in carbon-13, which indicates a higher rate of CO2-producing decarboxylation reactions rather than a consumption of CO2 for methane production. Alternatively, dolomite formation could account for an increasing depletion of the interstitial CO2. The interstitial gases in Holes 481 and 481A strongly reflect the thermal influence of the dolerite sill. Above the sill, carbon-13 values of -52% and C2/C1 ratios of 10**-2 indicate thermogenically formed hydrocarbon gases. Below the sill, less thermogenic gas formation suggests that convective, rather than conductive, heat transport operated after the sill intruded the wet sediments

Abiotic methane flux from the Chimaera seep and Tekirova ophiolites (Turkey): Understanding gas exhalation from low temperature serpentinization and implications for Mars

The emission of abiotic methane (CH4) into the atmosphere from low temperature serpentinization in ophiolitic rocks is documented to date only in four countries, the Philippines, Oman, New Zealand, and Turkey. Serpentinization produces large amounts of hydrogen (H-2) which in theory may react with CO2 or CO to form hydrocarbons (Fischer-Tropsch Type synthesis, FTT). Similar mechanisms have been invoked to explain the CH4 detected on Mars, so that understanding flux and exhalation modality of ophiolitic gas on Earth may contribute to decipher the potential degassing on Mars. This work reports the first direct measurements of gas (CH4, CO2) flux ever done on onshore ophiolites with present-day serpentinization. We investigated the Tekirova ophiolites at Cirali, in Turkey, hosting the Chimaera seep, a system of gas vents issuing from fractures in a 5000 m(2) wide ophiolite outcrop. At this site at least 150-190 t of CH4 is annually released into the atmosphere. The molecular and isotopic compositions of C-1-C-5 alkanes, CO2, and N-2 combined with source rock maturity data and thermogenic gas formation modelling suggested a dominant abiotic component (similar to 80-90%) mixed with thermogenic gas. Abiotic H-2-rich gas is likely formed at temperatures below 50 degrees C, suggested by the low deuterium/hydrogen isotopic ratio of H-2 (delta D-H2: -720%4, consistent with the low geothermal gradient of the area. Abiotic gas synthesis must be very fast and effective in continuously producing an amount of gas equivalent to the long-lasting (>2 millennia) emission of >100 t CH4 yr(-1), otherwise pressurised gas accumulation must exist. Over the same ophiolitic formation, 3 km away from Chimaera, we detected an invisible microseepage of abiotic CH4 with fluxes from 0.07 to 1 g m(-2) d(-1). On Mars similar fluxes could be able to sustain the CH4 plume apparently recognised in the Northern Summer 2003 (10(4) or 10(5) t yr(-1)) over the wide olivine bedrock and outcrops of hydrated silicates in the Syrtis Major and Nili Fossae; just one seep like Chimaera or, more realistically, a weak, spatially sporadic microseepage, would be sufficient to maintain the atmospheric CH4 level on Mars. (C) 2011 Elsevier B.V. All rights reserved