Cardiovascular responses during submaximal cycling with and without left-lateral tilting: insights for practical applications of stress echocardiography

We investigated the cardiorespiratory responses to semi-supine exercise with (SS+45°) and without (SS-0°) a left-lateral tilt in 15 adults at fixed power output (70 W) and matched heart rates. At 70 W, oxygen uptake and heart rate reduced from upright to SS-0° then increased to SS+45° (p < 0.05). At matched heart rates, oxygen uptake and efficiency were lowest in SS+45° (p < 0.05). Left-lateral tilting should not be performed under the assumption that each position replicates the same cardiorespiratory responses. Novelty: Cardiorespiratory responses to exercise are influenced by left-lateral tilting, which should not be performed under the assumption that physiological responses are replicated between left-lateral positions.

Influence of the viscosity ratio on drop dynamics and breakup for a drop rising in an immiscible low-viscosity liquid

In a low Morton number ($\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}M$) regime, the stability of a single drop rising in an immiscible viscous liquid is experimentally and computationally examined for varying viscosity ratio $\eta $ (the viscosity of the drop divided by that of the suspending fluid) and varying Eötvös number ($\mathit{Eo}$). Three-dimensional computations, rather than three-dimensional axisymmetric computations, are necessary since non-axisymmetric unstable drop behaviour is studied. The computations are performed using the sharp-interface coupled level-set and volume-of-fluid (CLSVOF) method in order to capture the deforming drop boundary. In the lower $\eta $ regimes, $\eta = 0.02 $ or 0.1, and when $\mathit{Eo}$ exceeds a critical threshold, it is observed that a rising drop exhibits nonlinear lateral/tilting motion. In the higher $\eta $ regimes, $\eta = 0.1$, 1.94, 10 or 100, and when $\mathit{Eo}$ exceeds another critical threshold, it is found that a rising drop becomes unstable and breaks up into multiple drops. The type of breakup, either ‘dumbbell’, ‘intermediate’ or ‘toroidal’, depends intimately on $\eta $ and $\mathit{Eo}$.

Hiding responses of locusts to approaching objects

Locusts, Locusta migratoria, sitting on a plant stem hide from dark moving or expanding shapes in their environment. The fore- and middle legs perform this avoidance response by making lateral tilting movements, while the hindlegs slide laterally and guide rotation of the posterior body over the stem. During larger turns, the legs take lateral steps when lateral tilting is limited by the joints. Slow hiding movements of less than 300 degrees s-1 of angular velocity are induced by slowly changing (looming) shapes, and interposed stops or slowing of the movement can delay the progress of this hiding manoeuvre. Fast hiding movements with angular velocities between 120 degrees s-1 and 860 degrees s-1 proceed continuously and rapidly in response to rapidly expanding stimuli. Hiding responses to expanding shapes occur only after the expanding image has exceeded a threshold visual angle of 8–9.5 degrees. Hiding response latencies range between 220 ms and 1.2 s for fast hiding and are approximately 1.2 s for most slow hiding responses. Predator-avoidance responses such as freezing, jerking, crouching, walking backwards, dropping or jumping can be used instead of or in conjunction with hiding behaviour. We conclude that the fast hiding behaviour of locusts is a specific goal-directed type of optomotor behaviour requiring positional information from small-field detectors of shape expansion in the interneurone layers of the locust eye.