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Climate change is projected to constitute a significant threat to food security if no adaptation actions are taken. Transformation of agricultural systems, for example switching crop types or moving out of agriculture, is projected to be necessary in some cases. However, little attention has been paid to the timing of these transformations. Here, we develop a temporal uncertainty framework using the CMIP5 ensemble to assess when and where cultivation of key crops in sub-Saharan Africa becomes unviable. We report potential transformational changes for all major crops during the twenty-first century, as climates shift and areas become unsuitable. For most crops, however, transformation is limited to small pockets (<15% of area), and only for beans, maize and banana is transformation more widespread (∼30% area for maize and banana, 60% for beans). We envisage three overlapping adaptation phases to enable projected transformational changes: an incremental adaptation phase focused on improvements to crops and management, a preparatory phase that establishes appropriate policies and enabling environments, and a transformational adaptation phase in which farmers substitute crops, explore alternative livelihoods strategies, or relocate. To best align policies with production triggers for no-regret actions, monitoring capacities to track farming systems as well as climate are needed.

Changes in aortic flow characteristics have previously been linked with cardiovascular disease (CVD). The purpose of the study is to determine the effects of heart rate (HR), cardiac output (CO), and the temporal flow profile on retrograde flow and wall shear stress (WSS) in the thoracic aorta. Pulsatile flow in a human thoracic aorta model was simulated for eleven combinations of HR (60–150 beats per minutes, BPM), CO and temporal flow profiles. Retrograde flow and WSS effects were characterized with common biomechanical metrics along with new markers. The results underpin the importance of temporal variation of the cardiac flow rate and the impact of the deceleration phase of systole and diastole on retrograde flow. During retrograde flow, the near-wall region may be stagnant (with low WSS) at low HR. At high HR, the WSS increases and becomes oscillatory in space and time. This finding may explain the clinical observation that increasing HR is associated with risk for CVD.

The right atrium (RA) combines flows from the inferior (IVC) and superior vena cava (SVC). Here RA mixing is simulated using computational fluid dynamics, comparing four modeling approaches. A patient-averaged model (11M cells) was created from four volunteers. We compared: 1. unsteady k-? Reynolds-averaged Navier-Stokes (URANS) 2. implicit large eddy simulation with second-order upwind convection scheme (iLES-SOU) 3. iLES with bounded-central difference convection scheme (iLES-BCD) and 4. LES with wall-adapting local eddy-viscosity (LES-WALE). A constant inlet flow rate of 6L/min was applied with both IVC/SVC contributions ranging from 30-70%. A higher density mesh (37M cells) was also simulated for models 2 and 4 (equal IVC/SVC flow) to assess the accuracy models 1-4. Results from the 11M cell LES-WALE model showed good agreement with the 37M cell meshes. All four 11M cell models captured the same large-scale flow structures. There were local differences in velocity, time-averaged wall shear stress and IVC/SVC mixing when compared to LES-WALE, particularly at high SVC flow. Energy spectra and velocity animations from the LES-WALE model suggest the presence of transitional flow. For the general flow structures, all four methods provide similar results, though local quantities can vary greatly. On coarse meshes, the convection scheme and SGS model have a significant impact on results. For RA flows, URANS should be avoided and iLES models are sensitive to convection scheme unless used on a highly resolved grid.