RESUMEN
The propagation kinetics and copolymerization behavior of the biorenewable monomer γ-methyl-α-methylene-γ-butyrolactone (MeMBL) are studied using the pulsed laser polymerization (PLP)/size exclusion chromatography (SEC) technique. The propagation rate coefficient for MeMBL is 15% higher than that of its structural analogue, methyl methacrylate (MMA), with a similar activation energy of 21.8 kJ·mol(-1). When compared to MMA, MeMBL is preferentially incorporated into copolymers when reacted with styrene (ST), MMA, and n-butyl acrylate (BA); the monomer reactivity ratios fit from bulk MeMBL/ST, MeMBL/MMA, and MeMBL/BA copolymerizations are r(MeMBL) = 0.80 ± 0.04 and r(ST) = 0.34 ± 0.04, r(MeMBL) = 3.0 ± 0.3 and r(MMA) = 0.33 ± 0.01, and r(MeMBL) = 7.0 ± 2.0 and r(BA) = 0.16 ± 0.03, respectively. In all cases, no significant variation with temperature was found between 50 and 90 °C. The implicit penultimate unit effect (IPUE) model was found to adequately fit the composition-averaged copolymerization propagation rate coefficient, k(p,cop), for the three systems.
Asunto(s)
4-Butirolactona/análogos & derivados , Tecnología Química Verde/métodos , Metilmetacrilato/química , Polímeros/síntesis química , Estireno/química , 4-Butirolactona/síntesis química , Acrilatos/química , Cromatografía en Gel , Radicales Libres , Cinética , Rayos Láser , Modelos Químicos , Polimerizacion , Temperatura , Termodinámica , ViscosidadRESUMEN
Full flexion is critical for total knee arthroplasty (TKA) patients in the Middle East, where daily activities require a high range of motion in the lower limb. This study aimed to increase understanding of the knee kinematics of normal Muslim subjects during high-flexion activities of daily living, such as kneeling, Muslim prayer, sitting cross-legged, and squatting. The early postoperative kinematics for a select group of Muslim, high-flexion TKA patients are also reported. Mean curves were compared between the normal group and the TKA group. During kneeling, the average maximum flexion was 141.6° for the normal group and 140.2° for the TKA group. The normal group's maximum and minimum knee angles (flexion, abduction, external rotation) were reported and, with the exception of maximum extension, were not significantly different from the TKA group, despite short postoperative times.
Asunto(s)
Actividades Cotidianas , Artroplastia de Reemplazo de Rodilla , Islamismo , Articulación de la Rodilla/fisiología , Fenómenos Biomecánicos , Humanos , Masculino , Persona de Mediana Edad , Medio Oriente , Rango del Movimiento ArticularRESUMEN
Axial tibiofemoral joint contact forces were non-invasively determined for two high range of motion (high flexion) squatting activities. An electromagnetic motion tracking system and a non-conductive force platform were used to collect kinematic and kinetic data. An innovative scaling method was used to model subject-specific muscle group moment arms. One subject attained a peak axial tibiofemoral joint contact force of 49.7 N/kg during squatting at 149.9 degrees knee flexion. Average joint angles and average axial joint contact forces were calculated for each of the activities in order to facilitate a comparison with stair climbing data. Compared to stair climbing, the maximum average joint contact forces during the squatting activities occurred at significantly higher flexion angles (p<0.05.) The relative simplicity of the method makes it useful for application to large subject groups from diverse regions. The results of this study can be applied to the diagnosis and treatment of pathologies, and to the development of high range of motion (ROM) knee replacements.