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Quantifying the motility of micro-organisms is beneficial in understanding their biomechanical properties. This paper presents a simple image-based algorithm to derive the kinetic power and propulsive force of the nematode Caenorhabditis elegans. To avoid unnecessary disturbance, each worm was confined in an aqueous droplet of 0.5 μl. The droplet was sandwiched between two glass slides and sealed with mineral oil to prevent evaporation. For motion visualization, 3-μm fluorescent particles were dispersed in the droplet. Since the droplet formed an isolated environment, the fluid drag and energy loss due to wall frictions were associated with the worm''s kinetic power and propulsion. A microparticle image velocimetry system was used to acquire consecutive particle images for fluid analysis. The short-time interval (Δt < 20 ms) between images enabled quasi real-time measurements. A numerical simulation of the flow in a straight channel showed that the relative error of this algorithm was significantly mitigated as the image was divided into small interrogation windows. The time-averaged power and propulsive force of a N2 adult worm over three swimming cycles were estimated to be 5.2 ± 3.1 pW and 1.0 ± 0.8 nN, respectively. In addition, a mutant, KG532 [kin-2(ce179) X], and a wild-type (N2) worm in a viscous medium were investigated. Both cases showed an increase in the kinetic power as compared with the N2 worm in the nematode growth medium due to the hyperactive nature of the kin-2 mutant and the high viscosity medium used. Overall, the technique deals with less sophisticated calculations and is automation possible. 相似文献
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Lau Sie Hoe Lau Ngee Kiong Hong Kian Sam Hasbee Bin Usop 《美中教育评论》2009,6(5):51-60
Assessment is central to any educational process. Number Right （NR） scoring method is a conventional scoring method for multiple choice items, where students need to pick one option as the correct answer. One point is awarded for the correct response and zero for any other responses. However, it has been heavily criticized for guessing and failure to credit partial knowledge. Despite continued research in scoring methods, conventional NR scoring method remains the most popular and widely used procedure. Thus, the problem of crediting partial knowledge and guessing still exist. In addition, the current assessment practices do not take students＇ misconceptions into consideration. Thus, there is a need to propose a new scoring method that is able to minimize guessing, credit partial knowledge, yet able to diagnose misconceptions. This study proposed the development of a Computer-Adaptive Assessment Software （CAAS） for MC items using the new Number Right Elimination Testing （NRET） which take into consideration these three elements. This paper described the rational for using the NRET, the design and development of CAAS and the results of the pilot study carried out in three secondary schools in Malaysia. 相似文献
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