Mapping Antarctic crevasses and their evolution with deep learning applied to satellite radar imagery

The fracturing of glaciers and ice shelves in Antarctica influences their dynamics and stability. Hence, data on the evolving distribution of crevasses are required to better understand the evolution of the ice sheet, though such data have traditionally been difficult and time-consuming to generate. Here, we present an automated method of mapping crevasses on grounded and floating ice with the application of convolutional neural networks to Sentinel-1 synthetic aperture radar backscatter data. We apply this method across Antarctica to images acquired between 2015 and 2022, producing a 7.5-year record of composite fracture maps at monthly intervals and 50 m spatial resolution and showing the distribution of crevasses around the majority of the ice sheet margin. We develop a method of quantifying changes to the density of ice shelf fractures using a time series of crevasse maps and show increases in crevassing on Thwaites and Pine Island ice shelves over the observational period, with observed changes elsewhere in the Amundsen Sea dominated by the advection of existing crevasses. Using stress fields computed using the BISICLES ice sheet model, we show that much of this structural change has occurred in buttressing regions of these ice shelves, indicating a recent and ongoing link between fracturing and the developing dynamics of the Amundsen Sea sector

Collapse of the last Eurasian Ice Sheet in the North Sea modulated by combined processes of ice flow, surface melt, and marine ice sheet instabilities

The record of the confluence and collapse of the British‐Irish Ice Sheet and the Fennoscandian Ice Sheet is obscured by the North Sea, hindering reconstructions of the glacial dynamics of this sector of the Eurasian Ice Sheet complex during the last glacial cycle. Previous numerical simulations of the deglaciation of the North Sea have also struggled to capture the confluence and separation of the British‐Irish and Fennoscandian Ice Sheets. We ran an ensemble of 70 experiments simulating the deglaciation of the North Sea between 23 and 18 ka BP using the BISICLES ice sheet model. A novel suite of quantitative model‐data comparison tools was used to identify plausible simulations of deglaciation that match empirical data for ice flow, margin position, and retreat ages, allowing comparisons to large amounts of empirical data. In ensemble members that best match the empirical data, the North Sea deglaciates through the collapse of the marine‐based Norwegian Channel Ice Stream, unzipping the confluence between the British‐Irish Ice Sheet and the Fennoscandian Ice Sheet. Thinning of the Norwegian Channel Ice Stream causes surface temperature feedbacks, rapid grounding line retreat, and ice stream acceleration, further driving separation of the British‐Irish and the Fennoscandian Ice Sheets. These simulations of the North Sea deglaciation conform with the majority of empirical evidence, and therefore provide physically plausible insights that are consistent with reconstructions based on the empirical evidence, and permit a quantitative comparison between model and data

Digital Drugs: an anatomy of new medicines

Medicines are digitalized as aspects of their regulation and use are embodied in or draw from interlinked computerized systems and databases. This paper considers how this development changes the delivery of health care, the pharma industry, and regulatory and professional structures, as it reconfigures the material character of drugs themselves. It draws on the concept of assemblage in presenting a theory-based analysis that explores digital drugs’ ontological status including how they embody benefit and value. The paper addresses three interconnected domains – that of use of drugs (practice), of research (epistemology) and of regulation (structures)

Sensitivity of the Weddell Sea sector ice streams to sub-shelf melting and surface accumulation

A recent ocean modelling study indicates that possible changes in circulation may bring warm deep-ocean water into direct contact with the grounding lines of the Filchner–Ronne ice streams, suggesting the potential for future ice losses from this sector equivalent to ~0.3 m of sea-level rise. Significant advancements have been made in our knowledge of both the basal topography and ice velocity in the Weddell Sea sector, and the ability to accurately model marine ice sheet dynamics, thus enabling an assessment to be made of the relative sensitivities of the diverse collection of ice streams feeding the Filchner–Ronne Ice Shelf. Here we use the BISICLES ice sheet model, which employs adaptive-mesh refinement to resolve grounding line dynamics, to carry out such an assessment. The impact of realistic perturbations to the surface and sub-shelf mass balance forcing fields from our 2000-year "reference" model run indicate that both the Institute and Möller ice streams are highly sensitive to changes in basal melting either near to their respective grounding lines, or in the region of the ice rises within the Filchner–Ronne Ice Shelf. These same perturbations have little impact, however, on the Rutford, Carlson or Foundation ice streams, while the Evans Ice Stream is found to enter a phase of unstable retreat only after melt at its grounding line has increased by 50% of likely present-day values

Contrast-enhanced spectral mammography improves diagnostic accuracy in the symptomatic setting

This paper was accepted for publication in the journal Clinical Radiology and the definitive published version is available at http://dx.doi.org/10.1016/j.crad.2016.05.009Aim. To assess the diagnostic accuracy of Contrast Enhanced Spectral Mammography (CESM), and gauge its “added value” in the symptomatic setting. Methods. At our institution, women aged 35-70 years with a suspicious or malignant clinical abnormality are offered CESM instead of standard Full-Field Digital Mammography (FFDM) as an initial imaging test. CESM is also offered to younger women whose ultrasound is suspicious, or who have biopsy-proven malignancy. It is occasionally used as an alternative to breast MRI following multi-disciplinary team discussion. We performed a retrospective multi-reader review of 100 consecutive CESM examinations. Anonymised Low Energy (LE) images were reviewed and given a score for malignancy. At least 3 weeks later, the entire examination (LE and recombined images) was reviewed. Pathology data was obtained for all cases. Differences in performance were assessed using receiver operative characteristic (ROC) analysis. Sensitivity, specificity and lesion size (vs MRI or histopathology) differences were calculated. Results. 73% cases were malignant at final histology, 27% were benign following standard triple assessment. ROC analysis showed improved overall performance of CESM over LE alone, with area under the curve of 93% vs 83% (p<0.025). CESM showed increased sensitivity (95% vs 84, p<0.025) and specificity (81% vs 63%, p<0.025) compared to LE alone, with all 5 readers showing improved accuracy. Tumour size estimation at CESM was significantly more accurate than LE alone, the latter tending to undersize lesions. In 75% of cases CESM was deemed a useful or significant aid to diagnosis. Conclusion. CESM provides immediately available, clinically useful information in the symptomatic clinic in patients with suspicious palpable abnormalities. Radiologist sensitivity, specificity and size accuracy for breast cancer detection and staging are all improved using CESM as the primary mammographic investigation