ABSTRACT
Locomotion at low Reynolds numbers encounters stringent physical constraints due to the dominance of viscous over inertial forces. A variety of swimming microorganisms have demonstrated diverse strategies to generate self-propulsion in the absence of inertia. In particular, ameboid and euglenoid movements exploit shape deformations of the cell body for locomotion. Inspired by these biological organisms, the 'push-me-pull-you' (PMPY) swimmer (Avron J Eet al2005New J. Phys.7234) represents an elegant artificial swimmer that can escape from the constraints of the scallop theorem and generate self-propulsion in highly viscous fluid environments. In this work, we present the first experimental realization of the PMPY swimmer, which consists of a pair of expandable spheres connected by an extensible link. We designed and constructed robotic PMPY swimmers and characterized their propulsion performance in highly viscous silicone oil in dynamically similar, macroscopic experiments. The proof-of-concept demonstrates the feasibility and robustness of the PMPY mechanism as a viable locomotion strategy at low Reynolds numbers.
Subject(s)
Robotics , Swimming , Locomotion , Models, Biological , ViscosityABSTRACT
The effect of fermented apple pomace (FAP) on animal health, antioxidant activity (AA), hematic biometry (HBm) and the development of ruminal epithelium were investigated in a study with 24 finishing lambs (BW = 25.4 ± 3.3 Kg). Lambs were grouped by sex (12 male and 12 female) and fed (n = 6 per group of treatment) a basal fattening diet (Control diet, T1) or the basal diet supplemented to include 10.91% of fermented apple pomace (FAP diet, T2). The animals were kept 56 d in individual metabolic cages, with ad libitum access to water and feed. Two blood samples were collected from each animal on d 0, 28, and 56 to determine AA in plasma and hematic biometry (HBm). Four samples of ruminal tissue were taken postmortem to evaluate the development of ruminal epithelium based on the length (LP) and width (WP) of papillae. AA and HBm data were analyzed with a mixed model (fixed effects: diet, sampling, sex, and their interaction; using the experimental unit nested in the effect of the diet as the random effect). LP and WP were analyzed with a hierarchical model, as simple and nested effects in the sampling site, where the fixed effects were the diet and the sex of the animal and their interaction. There was an effect of diet on AA, which was higher (P < 0.06) in T2 vs. T1 at 56 d (24.34 vs. 21.79 mM Fe2). Leukocytes increased (P < 0.05) from 7.52*10(3) ± 1.29*10/(3)µL to 9.14*10(3) ± 1.24*10(3)/µL in all the animals in the experiment, with a marked increased (P < 0.05) at 28 d after beginning of the feeding period, with values within the normal range for this species and without effect of the diet (P > 0.05) for the other indicators of HBm. Males' LP was higher in T2 than in T1 (P < 0.05). It was concluded that the use of FAP in the diets of finishing sheep reaped benefits on animal health and the development of rumen epithelium by improving antioxidant activity in plasma and stimulating the growth of papillae.
