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Madison, WI, United States

Slane L.C.,550 Engineering Drive | Thelen D.G.,550 Engineering Drive | Thelen D.G.,1513 University Ave | Thelen D.G.,1300 University Ave
Medical Engineering and Physics | Year: 2015

The purpose of this study was to investigate middle-age effects on Achilles displacement patterns under passive stretch and eccentric loading. Healthy young (24.1±1.4 years, n=9) and middle-aged (49.0±3.1 years, n=9) adults were positioned prone and the ankle was cyclically dorsiflexed (0.5Hz, 25° range) during passive stretch and active lengthening. Achilles displacements were tracked in cine ultrasound using 2D speckle tracking. Displacements were found to be non-uniform, with mid and deep portions of the tendon displacing more than superficial portions. However, the degree of non-uniformity was significantly reduced in middle-aged adults, suggesting a potential age-related reduction in inter-fascicle sliding or a shift in loading sharing between plantarflexors. Eccentric loading reduced displacement magnitudes, likely reflecting distal tendon stretch induced via active muscle contractions. Changes in tendon displacement with active loading were greater in middle-aged adults, which could reflect greater tendon compliance. The observed age-related changes in Achilles tendon behavior may have implications for both plantarflexor performance and injury risk. © 2015 IPEM. Source

Sun X.,1513 University Ave | Kharbas H.,1513 University Ave | Turng L.-S.,1513 University Ave
Polymer Engineering and Science | Year: 2015

Thermoplastic polyurethane (TPU) is one of the most widely used and versatile thermoplastic materials. TPU foams have been extensively applied in various industries including the furniture, automotive, sportswear, and packaging industries. In this study, two methods of producing highly expanded TPU injection molded foam were investigated: (1) microcellular injection molding (MIM) with N2 as a blowing agent, and (2) a novel gas-laden pellet/MIM combined process with N2 and CO2 as co-blowing agents. Two designs of experiments (DOEs) were performed to learn the influences of key processing parameters and to optimize foam quality. By using N2 and CO2 as co-blowing agents, a bulk density as low as 0.20g/cm3 was successfully achieved with a hysteresis compression loss of 24.4%. © 2015 Society of Plastics Engineers. Source

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