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Biology subjects

Hudson, D.

Publications and source records attributed to Hudson, D..

2 recordsLinked to original sources

Quantifying the wave resistance of a swimmer

AbstractQuantifying the wave resistance of a swimmer as a function of depth assists in identifying the optimum depth for the glide phases of competition. Previous experiments have inferred how immersed depth influences the drag acting on a swimmer [1], but have not directly quantified the magnitude of wave resistance. This research experimentally validates the use of thin-ship theory for quantifying the wave resistance of a realistic swimmer geometry. The drag and wave pattern of a female swimmer mannequin were experimentally measured over a range of depths from 0.05m to 1.00m at a speed of 2.50 m/s. Numerical simulations agree with experiment to confirm that there were negligible reductions in wave resistance below a depth of 0.40m. Larger swimming pool dimensions are shown to be significant at reducing wave resistance at speeds above 2.0 m/s and depths below 0.40m. Truncating the swimmer’s body at the upper thigh increases the wave resistance at speeds below 2.0m/s but is not significant at higher speeds, indicating that the upper body is the main contributor to the wave system. Numerical experiments indicate that rotating the shoulders towards the surface is more influential than the feet, demonstrating the impact of the upper body on wave resistance.Competing Interest StatementThe authors have declared no competing interest.View Full Text

bioengineering

Tendon and Motor Phenotypes in the Crtap-/- Mouse Model of Recessive Osteogenesis Imperfecta

Osteogenesis imperfecta (OI) is characterized by short stature, skeletal deformities, low bone mass with bone fragility, and motor deficits. A subset of OI patients also present with joint hypermobility; however, the role of tendon/ligament dysfunction in OI pathogenesis is largely unknown. Using the Crtap-/- mouse model of severe, recessive OI, we found that mutant Achilles tendons and patellar ligaments were thinner with increased collagen cross-links and reduced collagen fibril size at 1- and 4-months compared to wildtype. Patellar ligaments from Crtap-/- mice also had fewer progenitors with a concomitant increase in immature cells. RNA-seq analysis of Achilles tendons and patellar ligaments from 1-month Crtap-/- mice revealed dysregulation in matrix gene expression concomitant with predicted alterations in TGF-{beta}, inflammatory, and metabolic signaling. Finally, a series of behavioral tests revealed severe motor impairments and reduced grip strength in 4-month Crtap-/- mice - a phenotype that correlates with the tendon/ligament pathology.

genetics