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- Huang, Q M, et al.
(författare)
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Pulling force in lateral lifting and lowering.
- 1998
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Ingår i: Ergonomics. - : Informa UK Limited. - 0014-0139 .- 1366-5847. ; 41:6, s. 899-908
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Tidskriftsartikel (refereegranskat)abstract
- This work investigated maximal voluntary lateral hand pulling force in 18 healthy, habitually active men. Measurements were made in standing at different static angles of lateral trunk flexion, as well as at different constant lifting and lowering velocities. Movement was constrained to the frontal plane, velocity was controlled by an isokinetic dynamometer, pulling force was measured with a strain gauge and overall lateral angular displacement of the trunk by an electrogoniometer. Mean peak pulling force values ranged from 478 to 658 N (static), 291 to 528 N (lifting), and 801 to 911 N (lowering), respectively. The static pulling forces were the highest in flexed positions to the loaded side (10 degrees and 20 degrees trunk angles). In lifting, peak and position-specific pulling force decreased with increasing velocity. Peak lifting force occurred in a flexed trunk position of 7 to 9 degrees to the loaded side. In lowering, pulling forces were significantly higher than during lifting at corresponding velocities and showed less changes with velocity. Peak lowering force occurred at a trunk angle of -7 to -11 degrees, that is towards the unloaded side. In conclusion, maximal voluntary pulling force in the frontal plane was found to be task dependent. Lowering was accompanied by higher forces and a different velocity and position dependency than lifting which, in addition to the fact that the trunk muscles act predominantly eccentrically during the lowering task, may impose an increased risk of injury.
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- Zhang, L, et al.
(författare)
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Biodegradability of regenerated cellulose films coated with polyurethane/natural polymers interpenetrating polymer networks
- 1999
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 38:11, s. 4284-4289
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Tidskriftsartikel (refereegranskat)abstract
- Interpenetrating polymer network (IPN) coatings synthesized from castor- oil-based polyurethane (PU) with chitosan, nitrocellulose, or elaeostearin were coated on regenerated cellulose (RC) film for curing at 80-100 °C for 2-5 min, providing biodegradable, water-resistant cellulose films coded, respectively, as RCCH, RCNC, and RCEs. The coated films were buried in natural soil for decaying and inoculated with a spore suspension of fungi on the agar medium, respectively, to test biodegradability. The viscosity- average molecular weight, M(n), and the weight of the degraded films decreased sharply with the progress of degradation. The degradation half- lifes, t(1/2), of the films in soil at 30 °C were found to be 19 days for RC, 25 days for RCNC, 32 days for RCCH, and 45 days for the RCEs films. Scanning electron microscopy (SEM) showed that the extent of decay followed in the order RC > RCNC > RCCH > RCEs. SEM, infrared (IR), high-performance liquid chromatography (HPLC), and CO2 evolution results indicated that the microorganisms directly attacked the water-resistant coating layer and then penetrated into the cellulose to speedily metabolize, while accompanying with producing CO2, H2O, glucose cleaved from cellulose, and small molecules decomposed from the coatings.Interpenetrating polymer network (IPN) coatings synthesized from castor-oil-based polyurethane (PU) with chitosan, nitrocellulose, or elaeostearin were coated on regenerated cellulose (RC) film for curing at 80-100°C for 2-5 min, providing biodegradable, water-resistant cellulose films coded, respectively, as RCCH, RCNC, and RCEs. The coated films were buried in natural soil for decaying and inoculated with a spore suspension of fungi on the agar medium, respectively, to test biodegradability. The viscosity-average molecular weight, Mη, and the weight of the degraded films decreased sharply with the process of degradation. The degradation half-lifes, t1/2, of the films in soil at 30°C were found to be 19 days for RC, 25 days for RCNC, 32 days for RCCH, and 45 days for the RCEs films. Scanning electron microscopy (SEM) showed that the extent of decay followed in the order RC > RCNC > RCCH > RCEs. SEM, infrared (IR), high-performance liquid chromatography (HPLC), and CO2 evolution results indicated that the microorganisms directly attacked the water-resistant coating layer and then penetrated into the cellulose to speedily metabolize, while accompanying with producing CO2, H2O, glucose cleaved from cellulose, and small molecules decomposed from the coatings.
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