We conducted numerical experiments to study the influence of non-propagating longitudinal and circular contractions, i.e. pendular activity and segmentation, respectively, on flow and mixing in the proximal duodenum. A lattice-Boltzmann numerical method was developed to simulate the fluid mechanical consequences for each of 22 randomly selected sequences of high-definition video of real longitudinal and radial contractile activity in the isolated proximal duodenum of the rat and guinea pig. During pendular activity in the rat duodenum, the flow was characterized by regions of high shear rate. Mixing was so governed by shearing deformation of the fluid that increased the interface between adjacent domains and accelerated their interdiffusion (for diffusion coefficients approx. less than 10 28 m 2 s 21). When pendular activity was associated with a slow gastric outflow characteristic of post-prandial period, the dispersion was also improved, especially near the walls. Mixing was not promoted by isolated segmentative contractions in the guinea pig duodenum and not notably influenced by pylorus outflow. We concluded that pendular activity generates mixing of viscous fluids 'in situ' and accelerates the diffusive mass transfer, whereas segmentation may be more important in mixing particulate suspensions with high solid volume ratios.

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Pulse wave analysis (PWA) is widely used to investigate systemic arterial stiffness. The augmentation index (AIx), the primary outcome derived from PWA, is influenced by the mean arterial pressure (MAP), age, gender and heart rate (HR). Gender-and age-specific reference values have been devised, and it is recommended that the MAP be used as a statistical covariate. The AIx is also commonly statistically adjusted to a HR of 75 b·min; however, this approach may be physiologically and statistically inappropriate. First, there appears to be an important physiological chronic interaction between HR and arterial stiffness. Second, the method used to correct to HR assumes that the relationship with AIx is uniform across populations. A more appropriate practice may be to include HR as an independent predictor or covariate; this approach is particularly recommended for longitudinal studies, in which changes in HR may help to explain changes in arterial stiffness.

A B S T R A C TA 3-D computational fluid dynamics (CFD) model was developed to describe and predict the temperature profiles of palletised polylined kiwifruit packages undergoing forced-air cooling. The geometrical configuration of the kiwifruit, polyliner and cardboard box were explicitly modelled. The model included the effects of natural convection on the airflow behaviour and heat transfer process occurring within the packed fruits inside the polyliner. The capability of the model to predict the fruit temperatures in each package was quantitatively validated against experimental data. A laboratory scaled experimental rig was used to monitor the forced-air cooling process of a half pallet of kiwifruit boxes under controlled operating conditions. The numerical model was able to predict cooling times within experimental error.Cooling within the pallet was primarily influenced by air temperature and to a lesser extent airflow distribution into each package. A maximum recommended volumetric flowrate through the pallet of 0.34 L kg À1 s À1 , far lower than flowrates recommended for the cooling of non-polylined produce, was identified. Successive increases to the flowrate, particularly beyond 0.34 L kg À1 s À1 , resulted in increasingly diminished reductions (<12%) to cooling rate.Within the polyliner there was a low transfer of energy between kiwifruit and kiwifruit surrounding air. Instead cooling was reliant on the air temperature flowing over the top of the polyliner.

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