| 1. |
- Neumann, Patrick, et al.
(författare)
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Trunk posture: reliability, accuracy, and risk estimates for low back pain from a video based assessment method
- 2001
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Ingår i: International Journal of Industrial Ergonomics. - 0169-8141. ; 28, s. 355-365
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Tidskriftsartikel (refereegranskat)abstract
- It has been recently reported that both dynamic movement characteristics, as well as the duration of postures adopted during work, are important in the development of low back pain (LBP). This paper presents a video-based posture assessment method capable of measuring trunk angles and angular velocities in industrial workplaces. The interobserver reliability, system accuracy, and the relationship of the measured exposures to the reporting of low back pain are reported. The video analysis workstation consisted of a desktop computer equipped with digital video capture and playback technology, a VCR, and a computer game type joystick. The operator could then use a joystick to track trunk flexion and lateral bending during computer-controlled video playback. The joystick buttons were used for binary input of twisting. The inter-observer reliability for peak flexion and percentage of time spent in posture category variables were excellent (ICC>0.8). Lower reliability levels were observed for peak and average velocity and movement related variables. The video analysis system time series data showed very high correlation to the criterion optoelectronic imaging system (r ¼ 0:92). Root mean square errors averaged 5.81 for the amplitude probability distribution function data. Trunk flexion variables including peak level, peak velocity, average velocity indicators, and percent time in flexion category indicators all showed significant differences between cases and controls in the epidemiological study. A model consisting of the measures peak trunk flexion, percent time in lateral bend and average lateral bending velocity emerged after multivariable analysis for relationship to low back pain.
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| 2. |
- Notley, Shannon M., et al.
(författare)
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Adsorbed layer structure of a weak polyelectrolyte studied by colloidal probe microscopy and QCM-D as a function of pH and ionic strength
- 2004
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 6:9, s. 2379-2386
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Tidskriftsartikel (refereegranskat)abstract
- The adsorbed layer structure of a weak polyelectrolyte poly(2-vinylpyridine), on silica and mica, has been studied using colloidal probe microscopy (CPM) and the quartz crystal microbalance (QCM-D). The adsorbed layer structure was found to be highly dependent on both the solution conditions from which it was adsorbed and the molecular weight. Conditions were altered to favour both flat adsorbed layers and the development of significant steric layers. The structural reconformation of the large steric layer was furthermore studied as a function of pH. The equilibrium interaction force, measured using CPM as a function of surface separation, was used to determine the relative extension of the polyelectrolyte away from the interface. At low pH (3.2) and high ionic strength, the adsorbed polyelectrolyte molecules adopt a highly extended conformation; as the pH is increased (to 4.6 then to 5.5) the polymer chains collapse progressively towards the interface. Reversal of this pH cycle causes a re-protonation of the adsorbed polymers and highlights the finite timescale for this process to occur. The kinetics of this process was measured from the amount of trapped solvent within the polyelectrolyte layer as determined from the QCM-D. Upon decrease in pH, the adsorbed chains swell before partially collapsing. We propose that this is due to cross-linking of the polymer in the protonated state. Furthermore, the combination of techniques used in this study, namely optical reflectometry, CPM and QCM-D, allows the determination of the solvent content of the adsorbed film of polyelectrolyte as well as the extension of the polymer from the interface as a function of pH.
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