Tensile Properties of Hydroxyapatite Whisker Reinforced Polyetheretherketone

AbstractPolyetheretherketone (PEEK) was reinforced with 0-40 vol% hydroxyapatite (HA) whiskers using a novel powder processing and compression molding technique. A powder mixture was uniaxially pressed into a composite powder compact and compression molded into a flat composite bar using an open-channel die, such that the HA whiskers exhibited a preferred orientation along the length of the bar and tensile specimens. As expected, increased HA whisker reinforcement resulted in increased elastic modulus, but decreased ultimate tensile strength and strain- or work-to-failure. PEEK reinforced with 40 vol% HA whiskers exhibited an elastic modulus of 16-18 GPa. PEEK reinforced with 20 vol% HA whiskers had an ultimate tensile strength of 70-80 MPa. Human cortical bone exhibits an elastic modulus of 17-26 GPa and an ultimate tensile strength of 80-150 MPa in the longitudinal direction (direction of principal stress). Stiffness coefficients measured by ultrasonic wave propagation indicated a level orthotropy also similar to that of human cortical bone tissue.</jats:p

Effect of Increased Heart Rate on Sleep Quality

Effect of Increased Heart Rate on Sleep Quality Trey Wilson, Colby Beard, Makkenzi Converse-Olson, Gabriel Moura Abstract Studies have shown that sleep is now considered one of the three basic pillars of health together with diet and exercise. Poor sleep quality has a negative impact in different areas related to physical health (1). Insomnia has been alleviated significantly with resistance exercise and stretching (2). Thus, this IRB-approved study investigated the effects of increased heart rate induced by passive static stretching on sleep quality among 18-22 year old college students. Male and female college students of aged 18-22 (n=13) completed a regimen of 10, one minute passive static stretches prior to sleep for a duration of two weeks with students self monitoring heart rates. Overall sleep quality was assessed using questions adopted from the Pittsburgh Sleep Quality Index. Results of this study indicated that while the passive static stretch regimen significantly increased (p=0.000528) heart rate prior to sleeping, a positive correlation between the percent change in heart rate and percent change of subjective sleep quality scores was not demonstrated (R=0.0983). The pre and post sleep assessment scores were not significantly different for either group (experiment group p=0.424823, control group p=0.318507). Average morning heart rates (60-80 bpm = range of normal resting HR) between the two groups (p=0.437006) showed no significant difference as well. This study showed that there was a significant change in heart rate as induced by passive static stretching among the experimental group, however, there was no correlation with overall quality of sleep. Clement-Carbonell, V., Portilla-Tamarit, I., Rubio-Aparicio, M., & Madrid-Valero, J. J. (2021). Sleep Quality, Mental and Physical Health: A Differential Relationship. International journal of environmental research and public health, 18(2), 460. https://doi.org/10.3390/ijerph18020460 D\u27Aurea, C. V. R., Poyares, D., Passos, G. S., Santana, M. G., Youngstedt, S. D., Souza, A. A., Bicudo, J., Tufik, S., & de Mello, M. T. (2019). Effects of resistance exercise training and stretching on chronic insomnia. Revista brasileira de psiquiatria (Sao Paulo, Brazil : 1999), 41(1), 51–57. https://doi.org/10.1590/1516-4446-2018-003