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The maize (Zea mays) stem is a biological structure that must balance both biotic and structural load bearing duties. These competing requirements are particularly relevant in the design of new bioenergy crops. Although increased stem digestibility is typically associated with a lower structural strength and higher propensity for lodging, with the right balance between structural and biological activities it may be possible to design crops that are high-yielding and have digestible biomass. This study investigates the hypothesis that geometric factors are much more influential in determining structural strength than tissue properties. To study these influences, both physical and in silico experiments were used. First, maize stems were tested in three-point bending. Specimen-specific finite element models were created based on x-ray computed tomography scans. Models were validated by comparison with experimental data. Sensitivity analyses were used to assess the influence of structural parameters such as geometric and material properties. As hypothesized, geometry was found to have a much stronger influence on structural stability than material properties. This information reinforces the notion that deficiencies in tissue strength could be offset by manipulation of stalk morphology, thus allowing the creation of stalks which are both resilient and digestible. 

Motivated by our experimental observations of nanofibre formation via the centrifugal spinning process, we develop a string model to study the behaviours of a Newtonian, viscous curved jet, in a non-orthogonal curvilinear coordinate system including both air-drag effects and solvent evaporation for the first time. In centrifugal spinning a polymeric solution emerges from the nozzle of a spinneret rotating at high speeds around its axis of symmetry and thins as it moves away from the nozzle exit until it finally lands on the collector. Except for the Newtonian fluid assumption, our model includes the key parameters of the curved jet flow, e.g. viscous, inertial, rotational, surface tension, gravitational, mass diffusion within the jet, mass diffusion into air and aerodynamic effects, via Rossby ( $Rb$ ), Reynolds ( $Re$ ), Weber ( $We$ ), Froude ( $Fr$ ), Péclet ( $Pe$ ), air Reynolds ( $$Re^{\ast }$$ ) and air Péclet ( $$Pe^{\ast }$$ ) numbers, and the collector radial position ( $${\mathcal{R}}$$ ). Our results, including comparison to experiments, reveal that the aerodynamic effects must be considered to enable a correct prediction of the jet trajectory and radius. Decreasing $Rb$ not only renders the jet thinning much faster, but also forces the jet to wrap tighter around the rotation axis. Increasing $Re$ , $$Re^{\ast }$$ and $${\mathcal{R}}$$ leads to a longer jet. Decreasing $We$ causes the jet to wrap tighter around the spinneret but it shows trivial effects on the solvent evaporation. Changes in $Pe$ and $$Pe^{\ast }$$ do not significantly affect the jet trajectory. Finally, we propose simple relations to estimate the jet radius and the jet breakup length.